Pennsylvania, 2021

Hail and Damaging Winds in Pennsylvania, April 21, 2021

April 21, 2021 · NWS PHI · 9 events in 6 counties and zones

A strong cold front approached the mid-Atlantic coast on April 21. Ahead of the front, modest instability developed in a strongly sheared and strongly forced environment.

Where it happened

Every event with a place to put it. Tap one for its entry below.

  • Tornadoes
  • Tropical storms and surge
  • Floods
  • Wind
  • Hail
  • Winter weather
  • Heat and drought
  • Cold
  • Fire, smoke and dust
  • Marine and coastal
  • Other

Open the live radar over this ground

The toll

Deaths
0
Injuries
0
Property damage
None recorded
Crop damage
None recorded
Events
9

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS PHI wrote it up.

A strong cold front approached the mid-Atlantic coast on April 21. Ahead of the front, modest instability developed in a strongly sheared and strongly forced environment. This led to the development of convection along and ahead of the front as it moved through during the mid afternoon hours. Mixed modes of linear and discrete storm cells were present, some of which became strong to severe. Scattered instances of hail and wind damage were reported across much of the eastern mid-Atlantic.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Apr 21, 7:49 AM EST, 3 hours 33 minutes earlier.

Area forecast discussion, Apr 21, 7:49 AM EST, 3 hours 33 minutes before
Area Forecast Discussion
National Weather Service Mount Holly NJ
849 AM EDT Wed Apr 21 2021

.SYNOPSIS...
A strong low and cold front will sweep through the Northeast today.
Broad high pressure will encompass much of the eastern U.S. Thursday
and Friday. A surface low developing in the central and southern
Plains Friday night will lift quickly northeastward through the Mid-
Atlantic Saturday night into the Canadian Maritimes by Monday. A
slow-moving surface high will build into the eastern U.S. and
western Atlantic through much of next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A cold front is currently stalled just NW of our area, resulting in
a fairly impressive thermal contrast between western and eastern PA
(temps in the low 30s near Pittsburgh with snow while low 60s
are being observed near Philadelphia). Low pressure, currently
in the vicinity of central PA, will continue to deepen and ride
northeast along this boundary through the day today as UL
divergence increases downstream of the deep trough over the
Great Lakes. As a result of the eastward progression of the mid-
lvl system, the cold front will also begin to rapidly progress
eastward late this morning into this afternoon... entering our
area around noon and clearing the coast by mid- afternoon.

Given the increasing UL dynamics and strengthening sfc.low the front
should be frontogenetic as it crosses our area and will thus serve
as a focus for convective development this afternoon. The primary
question marks regarding today's convective potential are how
quickly portions of area destabilize ahead of the front and
(relatedly) how quickly the front moves through the area. Low-lvl
Theta-E advection driven by an ~40kt LLJ should result in
appreciable sfc-based instability developing over the warm sector by
early afternoon. Areas around I-95 and eastward will have a couple
additional hours to diurnally mix/warm so naturally expect the
highest values of MLCAPE (generally 500-750 J/kg) to be in this
zone. The increasing residence time in the warm sector is the
primary motivation for SPC placing the eastern half or so of area in
a slight risk for convection today, while the western portion of our
area remains in a marginal risk. The kinematic fields still appear
sufficient to support organized convection with damaging winds as
the primary threat, given 0-3km shear values 30-35kts, 0-6km mean
winds around 40kts, and bulk shear values in the neighborhood of 45-
50kts. Convective mode looks to be linear given both the strongly
forced nature of the convection, and the parallel orientation of the
deep-layer shear vector to the boundary. The most likely timing for
convection would be (progressing from W-E) 1-4PM.

High temperatures will be a bit tricky today with a W-E gradient
likely due to the timing of the front. Expect portions of NJ and
Delmarva to hit the 70s, while low to mid 60s will be the norm in
eastern PA where the front crosses earlier in the day, with the
highest uncertainty around the I-95 corridor.

Temperatures and dewpoints will plummet behind the front later this
afternoon, with substantial pressure rises supporting post-frontal
gusts in the 30-35 mph range. Some light rain (snow in the Poconos)
showers will be possible behind the front, given continued height
falls/DCVA, however the magnitude of the dry air advection should
preclude these from being significant.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
Main concerns this period will be freeze potential tonight (and to a
lesser degree Thursday night) as well as winds through Thursday.
Fire weather concerns are present on Thursday, as well.

The low and cold front bringing our potentially active weather today
will be well off to our northeast and east by 00z Thursday. Strong
northwest winds will occur in the wake of the low, but the timing of
surface pressure rises is not particularly favorable for efficient
mixing of winds to the surface. Winds aloft will also be weakening
by Thursday, so the potential looks low for the need for a wind
advisory. Additionally, model soundings are far less impressive
today (generally reducing forecast gusts by 5+ kt tonight and
Thursday versus those seen yesterday, both the NAM and GFS). The
larger concern wind-wise is with fire-weather potential on
Thursday. See the fire weather section below for more details.

The next forecast concern is freeze potential tonight. First, it
should be noted that this is not a slam-dunk case for areas
northwest of the Fall Line. Although the cold advection will be
quite strong upstream of the front, breezy conditions will continue
through the night. Models commonly drop temperatures too much in
these regimes, and I suspect there is at least some of this bias
with the output this morning. Nevertheless, the growing season is
well underway outside of the southern Poconos, and with strong
potential for near-freezing to subfreezing temperatures, think
confidence is high enough to upgrade the freeze watch to a freeze
warning. Added Chester County to the product, given propensity for
more sheltered/valley spots to cool readily. Will need to watch for
potential in the Pine Barrens as well, but confidence is too low
here at this point for product issuance.

For Thursday night, winds will be diminishing, and skies are
expected to be clearing. On the first night of post-frontal
northwest flow regimes, a cold bias is typically exhibited. On the
second night, a warm bias tends to occur. As a result, think a
second freeze is possible in northern New Jersey and perhaps
portions of the Lehigh Valley. We will see what happens tonight
before addressing this, however.

High pressure will be shifting southeastward into the western
Atlantic by Friday night, and midlevel ridging will take place in
much of the eastern U.S. After a cold Thursday (highs generally in
the upper 40s to low 50s), around 7-12 degrees of warming is
expected for Friday. It may still be breezy during the day, but
winds will be noticeably lower than on Thursday. The warming
trend will continue with lows Friday night, with quiet
conditions remaining.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
A potentially strong but quick-hitting storm will affect the Mid-
Atlantic this weekend, but next week looks much quieter.

At the start of the period (12z Saturday), a southern-stream
perturbation will be moving through the middle Mississippi Valley,
with an attendant surface low bringing widespread precipitation to
the Midwest and strong convection to the Mid-South and Southeast.
The low will track east-northeast, as a northern-stream vort max
interacts with the storm system. This interaction will allow the low
to begin to track more northeasterly into the Mid-Atlantic by
Saturday night. A widespread soaking rain is expected for the region
as the low tracks through, with winds beginning to increase on the
north/west side of the low during the deepening phase of the
cyclone. Though models are in relative agreement with the large-
scale details of the system's evolution, the exact track will be
fairly important in terms of pinpointing relative maxima/minima in
QPF. A track over the area would likely mean dry-slotting for
portions of the CWA, whereas a track farther to the southeast would
be more favorable for widespread heavier total rainfall. Regardless,
rain seems rather likely for the whole area, and perhaps a storm or
two in the far south, closer to the system's warm sector. Increased
PoPs, but also broadened the period of higher PoPs into late
Saturday and also into Sunday (especially for the northeast CWA), as
confidence in timing is not overly high. The storm will be
relatively fast-moving, so this entire period will not be a washout,
but there looks to be a 6-12 hour period where it will be unpleasant
(especially with the anticipated breezy conditions).

As this low moves to the northeast on Sunday, another round of
northwest-flow winds will occur. Depending on the timing of the low,
this may end up being a little more formidable versus the low
affecting us the next couple of days, as the intensity of the low
combined with the more favorable timing may allow for some gusty
winds Sunday afternoon. Breezy conditions will continue through
Monday. One noticeable difference, however, will be the lack of
strong cooling in the wake of the system given its farther south
origins.

The upper pattern appears to become quite blocky next week, and as
has been the case of late, the upper low blasting through the area
this weekend may hang up in the northwest Atlantic upstream of
highly anomalous downstream ridge amplification. A deep trough will
approach the central U.S. during this time, leading to high-
amplitude ridging along the East Coast. All systems will slow down
in this evolving pattern, and the favorable positioning of the ridge
will lead to a quiet and warm stretch for the East Coast. Expect
this to begin in earnest by Tuesday.

&&

.AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Today... VFR conditions will prevail for most of the day, however a
convective line is expected to pass through most of the terminals
(particularly I-95 and eastward) this afternoon. The most likely
timing for this line will be (from W-E) 17-20Z, with gusty winds,
lightning, and temporarily reduced flight categories possible. Winds
will generally be SW around 10-15kts with gusts 20-25ks through
early this afternoon, then shift WNW sustained at 15-20kts with
gusts to 30kts behind the front. High confidence in most aspects of
the forecast, lower confidence on if the convective line will impact
KRDG/KABE.

Tonight... Generally VFR although some sporadic MVFR cigs may be
possible at KRDG/KABE at times this evening. WNW winds sustained 10-
15kts with gusts 20-25kts expected. High confidence.

Outlook...

Thursday...VFR with northwest winds 15 to 25 kt with gusts to 30+
kt. High confidence.

Thursday night and Friday...VFR with west winds 7 to 15 kt with
gusts to 20+ kt (higher speeds/gusts during the day). High
confidence.

Friday night and Saturday...Mainly VFR, but clouds should be on the
increase on Saturday. Light west or southwest winds on Friday night
becoming south and increasing to 7 to 15 kt on Saturday. Moderate
confidence.

Saturday night and Sunday...Rain and associated restrictions likely,
especially through Sunday morning. May see some improvement by late
Sunday. Winds will be quite variable and potentially gusty through
this period. Moderate confidence.

&&

.MARINE...
Southerly winds will increase to around 25-30kts over the waters
today and thus an SCA is currently in effect through the daytime
hours. A line of showers and thunderstorms is expected to pass over
the waters in the mid-afternoon time frame and strong winds and
lightning will be possible with these storms. Behind the storms
expect Northwest winds to increase to gale force this evening into
the overnight period. Seas will also increase into the 5-6 foot
range overnight.

Outlook...

Thursday...Northwest gales likely. A gale warning remains in effect
for all waters.

Thursday night...Lingering gales are possible during the evening,
with advisory conditions expected through the night.

Friday...Lingering advisory conditions possible, but conditions are
expected to improve with time.

Friday night and Saturday...Sub-advisory conditions expected.

Saturday night and Sunday...Advisory conditions probable as a strong
low moves through the region. As winds become northwest on Sunday,
advisory conditions become most likely. Gales cannot be ruled out.
Rain is likely Saturday night and Sunday morning.

&&

.FIRE WEATHER...
Windy and dry conditions are expected on Thursday across the
area. With low total rainfall amounts expected today, concern is
increasing that favorable fire-weather conditions will occur for
several hours during the day, as winds are forecast to gust to
30+ mph and minimum relative humidity will likely fall well
below 30 percent from late Thursday morning through the
afternoon. We will contact fire-weather partners today
regarding the need for a special weather statement or fire-
weather products on Thursday.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Freeze Warning from 1 AM to 9 AM EDT Thursday for PAZ060>062-
     101>103-105.
NJ...Freeze Warning from 1 AM to 9 AM EDT Thursday for NJZ001-
     007>010.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ430-
     431-450>455.
     Gale Warning from 6 PM this evening to 6 PM EDT Thursday for
     ANZ430-431-450>455.

&&

Synopsis...CMS
Near Term...Carr/Staarmann
Short Term...CMS
Long Term...CMS
Aviation...CMS/Carr
Marine...CMS/Carr
Fire Weather...CMS
Hazardous weather outlook, Apr 21, 2:36 AM EST, 8 hours 46 minutes before
Hazardous Weather Outlook
National Weather Service Mount Holly NJ
0336 AM EDT Wed Apr 21 2021

DEZ001-220736-
New Castle-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for New Castle County in Delaware.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

DEZ002-220736-
Kent-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Kent County in Delaware.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

DEZ003-220736-
Inland Sussex-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for inland portions of Sussex County
in Delaware.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

DEZ004-220736-
Delaware Beaches-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for the Atlantic coastal portions of
Sussex County in Delaware.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

PAZ054-220736-
Carbon-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Carbon County in Pennsylvania.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

PAZ055-220736-
Monroe-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Monroe County in Pennsylvania.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

PAZ060-220736-
Berks-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Berks County in Pennsylvania.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

PAZ061-220736-
Lehigh-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Lehigh County in Pennsylvania.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

PAZ062-220736-
Northampton-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Northampton County in
Pennsylvania.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

PAZ070-220736-
Delaware-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Delaware County in Pennsylvania.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

PAZ071-220736-
Philadelphia-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Philadelphia County in
Pennsylvania.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

PAZ101-220736-
Western Chester-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for western Chester County in
Pennsylvania.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

PAZ102-220736-
Eastern Chester-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for eastern Chester County in
Pennsylvania.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

PAZ103-220736-
Western Montgomery-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for western Montgomery County in
Pennsylvania.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

PAZ104-220736-
Eastern Montgomery-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for eastern Montgomery County in
Pennsylvania.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

PAZ105-220736-
Upper Bucks-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for upper Bucks County in
Pennsylvania.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

PAZ106-220736-
Lower Bucks-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for lower Bucks County in
Pennsylvania.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ001-220736-
Sussex-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Sussex County in New Jersey.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ007-220736-
Warren-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Warren County in New Jersey.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ008-220736-
Morris-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Morris County in New Jersey.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ009-220736-
Hunterdon-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Hunterdon County in New Jersey.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ010-220736-
Somerset-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Somerset County in New Jersey.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Freeze Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ012-220736-
Middlesex-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Middlesex County in New Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ013-220736-
Western Monmouth-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for western Monmouth County in New
Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ014-220736-
Eastern Monmouth-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for eastern Monmouth County in New
Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ015-220736-
Mercer-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Mercer County in New Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ016-220736-
Salem-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Salem County in New Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ017-220736-
Gloucester-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Gloucester County in New Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ018-220736-
Camden-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Camden County in New Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ019-220736-
Northwestern Burlington-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for northwestern Burlington County in
New Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ020-220736-
Ocean-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for inland portions of Ocean County
in New Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ021-220736-
Cumberland-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Cumberland County in New Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ022-220736-
Atlantic-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for inland portions of Atlantic
County in New Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ023-220736-
Cape May-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Cape May County excluding the
Atlantic coast in New Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ024-220736-
Atlantic Coastal Cape May-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for the Atlantic coastal portions of
Cape May County in New Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ025-220736-
Coastal Atlantic-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for coastal portions of Atlantic
County in New Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ026-220736-
Coastal Ocean-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for coastal portions of Ocean County
in New Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ027-220736-
Southeastern Burlington-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for southeastern Burlington County in
New Jersey.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

MDZ012-220736-
Kent MD-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Kent County in Maryland.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

MDZ015-220736-
Queen Annes-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Queen Annes County in Maryland.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

MDZ019-220736-
Talbot-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Talbot County in Maryland.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

MDZ020-220736-
Caroline-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for Caroline County in Maryland.

.DAY ONE...Through tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

ANZ430-220736-
Delaware Bay waters north of East Point NJ to Slaughter Beach DE-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for upper Delaware Bay.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

ANZ431-220736-
Delaware Bay waters south of East Point NJ to Slaughter Beach DE-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for lower Delaware Bay.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

ANZ450-220736-
Coastal waters from Sandy Hook to Manasquan Inlet NJ out 20 nm-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for the Atlantic coastal waters
adjacent to Monmouth County out 20 nm.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

ANZ451-220736-
Coastal waters from Manasquan Inlet to Little Egg Inlet NJ out 20 nm-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for the Atlantic coastal waters
adjacent to Ocean County out 20 nm.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

ANZ452-220736-
Coastal waters from Little Egg Inlet to Great Egg Inlet NJ out 20 nm-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for the Atlantic coastal waters
adjacent to Atlantic County out 20 nm.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

ANZ453-220736-
Coastal waters from Great Egg Inlet to Cape May NJ out 20 nm-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for the Atlantic coastal waters
adjacent to Cape May County out 20 nm.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

ANZ454-220736-
Coastal waters from Cape May NJ to Cape Henlopen DE out 20 nm-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for the Atlantic coastal waters
adjacent to the mouth of Delaware Bay out 20 nm.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

ANZ455-220736-
Coastal waters from Cape Henlopen to Fenwick Island DE out 20 nm-
0336 AM EDT Wed Apr 21 2021

This Hazardous Weather Outlook is for the Atlantic coastal waters
adjacent to Sussex County out 20 nm.

.DAY ONE...Through tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Gale Warning.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

In the hours before

Special weather statement, Apr 21, 11:03 AM EST, 19 minutes before
Special Weather Statement
National Weather Service Mount Holly NJ
1203 PM EDT Wed Apr 21 2021

DEZ001-PAZ060-061-070-101>103-105-211645-
New Castle-Upper Bucks-Lehigh-Western Montgomery-Delaware-Western
Chester-Eastern Chester-Berks-
1203 PM EDT Wed Apr 21 2021

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT NORTHWESTERN NEW
CASTLE...EASTERN BERKS...LEHIGH...NORTHWESTERN MONTGOMERY...WEST
CENTRAL BUCKS...CHESTER AND WEST CENTRAL DELAWARE COUNTIES...

At 1203 PM EDT, radar indicated strong thunderstorms were located
along a line extending from near Kutztown to Oxford. Movement was
east at 40 mph.

Wind gusts up to 50 mph and pea size hail are possible with these
storms.

Locations impacted include...
Allentown, Newark, West Chester, Bethlehem, Pottstown, Phoenixville,
Coatesville, Emmaus, Westtown, Northampton, Downingtown, Elsmere,
Kennett Square, Birdsboro, Collegeville, Oxford, Kutztown,
Royersford, Fleetwood and Parkesburg.

This includes the following highways...
 Pennsylvania Turnpike between mile markers 296 and 322.
 Northeast Extension between mile markers 42 and 62.
 Interstate 78 in Pennsylvania between mile markers 41 and 63.
 Interstate 176 in Pennsylvania between mile markers 1 and 5.

If outdoors, consider seeking shelter inside a building.

LAT...LON 3987 7599 3998 7598 4004 7593 4011 7594
      4014 7588 4017 7593 4060 7582 4069 7550
      4066 7548 4067 7544 4062 7538 4058 7541
      4057 7539 4022 7544 3970 7561 3970 7579
      3972 7579 3972 7604
TIME...MOT...LOC 1603Z 253DEG 35KT 4055 7576 3979 7596

Davis

The radar

The Philadelphia radar (KDIX), 112 km away, was scanning. The volume nearest the first event began at 16:23 UTC.

Open the radar archive at this moment

Event by event

6 thunderstorm wind, 3 hail. Local standard time, as filed.

Hail, Berks

When
April 21, 11:22 AM EST
Where
Berks County, 0.87 mi SW of Boyertown
Measured
1 in hail
Reported by
Trained Spotter
Coordinates
40.320, -75.640

Thunderstorm Wind, Lehigh

When
April 21, 11:35 AM EST
Where
Lehigh County, 0.89 mi N of Allentown Muni
Measured
50 kt (58 mph) estimated gust
Reported by
Utility Company
Coordinates
40.583, -75.480

A tree was downed on wires near Lehigh Parkway. Time estimated from radar.

Hail, Northampton

When
April 21, 11:45 AM EST
Where
Northampton County, 1.25 mi ESE of Ulhers
Measured
0.88 in hail
Reported by
Trained Spotter
Coordinates
40.740, -75.210

Hail, Montgomery

When
April 21, 12:03 PM EST
Where
Montgomery County, 0.87 mi SW of Collegeville
Measured
0.88 in hail
Reported by
Trained Spotter
Coordinates
40.190, -75.460

Thunderstorm Wind, Bucks

When
April 21, 12:05 PM EST
Where
Bucks County, Upper Black Eddy
Measured
50 kt (58 mph) estimated gust
Reported by
Public
Coordinates
40.570, -75.100

A large tree was downed.

Thunderstorm Wind, Montgomery

When
April 21, 12:40 PM EST
Where
Montgomery County, 0.94 mi E of Hill Crest
Measured
50 kt (58 mph) estimated gust
Reported by
Utility Company
Coordinates
40.081, -75.152

Tree limbs were downed onto wires on Rock Creek Dr. Time estimated from radar.

Thunderstorm Wind, Philadelphia

When
April 21, 12:40 PM EST
Where
Philadelphia County, 2.74 mi ENE of (Phl)philadelphia in
Measured
51 kt (59 mph) measured gust
Reported by
Mesonet
Coordinates
39.890, -75.200

Measured by Pennsylvania DOT RWIS station at I-95 and Girard Ave.

Thunderstorm Wind, Montgomery

When
April 21, 12:45 PM EST
Where
Montgomery County, Erdenheim
Measured
50 kt (58 mph) estimated gust
Reported by
Utility Company
Coordinates
40.100, -75.200

A tree was downed onto wires on Tyson Rd. Time estimated from radar.

Thunderstorm Wind, Philadelphia

When
April 21, 12:58 PM EST
Where
Philadelphia County, 1.6 mi WNW of Torresdale
Measured
50 kt (58 mph) estimated gust
Reported by
Utility Company
Coordinates
40.057, -75.029

Power outage due to severe weather near Holme Circle. Time estimated from radar.

What these are

Hail
Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
Thunderstorm Wind
Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in Pennsylvania in 2021Every state in 2021This day in weather historyWarnings in Pennsylvania, April 2021

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 947439, 947441, 947440, 947447, 947442, 947443, 947446, 947444, 947445.