Special Weather Statement, NWS Philadelphia/Mount Holly

Area Forecast Discussion
National Weather Service Mount Holly NJ
344 PM EDT Mon Jul 24 2023

.SYNOPSIS...
Weak low pressure off the coast of the Carolinas is expected to
drift northeast and across the waters off the Middle Atlantic
Coast through Tuesday. High pressure should follow from the
west for Wednesday. It is anticipated to merge with a larger
high over the western North Atlantic which should then influence
our weather for Thursday into Friday which look to be the
warmest days of the year. A cold front is expected to arrive
from the northwest on Saturday and will bring a relief to the
brief heat.

&&

.NEAR TERM /THROUGH TUESDAY/...
The clouds that were across most areas this morning have pushed away
as of the early afternoon. Increasing amounts of sunshine and
moderate amounts of humidity will contribute to some good CAPE
values (1000-1500 j/kg) over the area by late afternoon. Accordingly,
we expect some scattered showers/tstms to develop and will
continue with the chance pops (low likely N/W) into the early
evening. We remain in a Marginal risk for severe weather for the
rest of today. Later this evening, showers will end leaving
partly cloudy skies for the overnight. Lows will drop into the
upper 60s/low 70s for most areas. Patchy fog will develop
overnight mostly in rural areas, but also anywhere that rains
fall later today may also get fog.

On Tuesday, the upper H5 trough will start to push through the
area, reaching wrn PA during the morning and arriving over ern
PA by evening. More shortwaves and good daytime heating will
create showers/tstms by afternoon. A line of activity could
develop and move W to E thru the afternoon and evening. The most
recent Day2 outlook has increased the Delmarva areas into the
Slight risk category while other areas remain in Marginal risk.
Wind and hail are the primary threats for Tuesday.

Highs Tuesday will reach the mid/upper 80s for the region with
cooler temps at the shore and for the southern Poconos. Humidity
levels will be uncomfortable with dew points in the upper 60s/low
70s by afternoon.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As the long wave mid level trough over the eastern states begins to
push offshore on Tuesday, a final push of shortwave energy will pass
overhead in the evening. As a result, we will carry a chance of
afternoon and evening showers and thunderstorms. Forecast soundings
depict ~1000 J/kg MUCAPE lingering into Tuesday evening, though the
overall wind field in the low levels is relatively weak, so not
expecting any severe weather. Lows on Tuesday night are
forecast to be mostly from the middle 60s to the lower 70s.

Flat upper ridging will briefly build through the day on
Wednesday and weak surface high pressure is expected to extend
along the central and southern Appalachians. The combination
will result in a dry day on Wednesday with subsidence noted in
forecast soundings. The high will drift eastward on Wednesday
afternoon and Wednesday night, merging with a larger high
located over the western North Atlantic. Wednesday is forecast
to be mostly sunny with maximum temperatures in the upper 80s
and lower 90s. Wednesday night's lows will be a few degrees
above average in the upper 60s to the middle 70s as humidity
levels continue to increase overnight.

The persistent mid level long wave trough that has been protecting
us from excessively hot temperatures is expected to lift for the end
of the week. The flow across the northern states should become
somewhat zonal and a ridge over the western North Atlantic is
forecast to retrograde a bit. Meanwhile, a surface high off the
coast will establish a southerly flow of hot humid air into our
region.

We are anticipating a buildup of heat and humidity beginning on
Thursday when our first excessive heat headlines of the year are
looking increasingly possible. Warm, moist advection will ensue on
Thursday under southerly flow through much of the column. 850 temps
are progged to reach 18-20C which will support highs in the low to
mid 90s. Dew points will rise into the low to mid 70s and this will
result in heat index values reaching the upper 90s to low 100s in
the afternoon. Some shortwave energy will slide through aloft,
mainly focused to our north and west, where we will carry 20-30%
PoPs with peak heating aiding in scattered shower and thunderstorm
development.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
The heat will continue into Friday as this will likely be the
warmest day of the week (potentially of the year). The continuing
southwesterly flow will maintain warm, moist air through the day on
Friday. 850 temps will reach around 20C and latest NBM probs
indicate a ~90% chance of temperatures exceeding 90 degrees. The
past few runs of the GFS and Euro ensembles also support this trend.
With dew points in the mid 70s, heat index values of up to 100-105
degrees are possible.

A cold front is expected to arrive from the northwest on Saturday,
resulting in an increase in the potential for afternoon and evening
showers and thunderstorms on that day. The timing of the arrival of
the coldfront to our region is still uncertain, and may impact how
warm temperatures will be. In addition, there is the possibility of
showers and thunderstorms associated with the front. Will continue
to iron out any details in the week. Due to the timing differences,
we opted to stick with NBM guidance, showing highs in the upper 80s
to low 90s with chance PoPs in the afternoon.

In general, after the cold front moves through Saturday, we expect
temperatures to return closer to climatological averages to close
out the weekend.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

Tonight... Scattered showers/tstms will diminish after sunset with
predominately VFR conditions after that. Later tonight, patchy fog
may affect the terminals, especially if rains occur. I have written
some MVFR fog for most 'non-Delaware Valley' terminals. South to
Southwest winds 5 to 10 knots early, then light and variable
overnight. Medium confid.

Tuesday... Patchy morning fog possible then VFR with southwest winds
5 to 10 knots developing. Scattered afternoon showers or tstms
expected, but not in terminal fcst attm. Medium confid.

Outlook...

Wednesday...VFR. Southwesterly wind 5-10 knots. High confidence.

Thursday...Primarily VFR. A few scattered showers and
thunderstorms in the afternoon. Southwesterly wind 10-15 knots.
Moderate confidence.

Friday...Primarily VFR. A few scattered showers and thunderstorms in
the afternoon. Southwesterly wind 10-15 knots with gusts to 20
knots. Moderate confidence.

Saturday...Primarily VFR. A few scattered showers and thunderstorms
with the passage of cold front. Southwesterly wind 10-15 knots with
gusts to 20 knots. Low confidence.

&&

.MARINE...
Good conditions on the waters with an onshore or mostly S-SE winds
this afternoon. Speeds will increase to 10 to 15 kts with some gusts
around 20 knots into the early evening. A few scattered showers/tstms
later this afternoon. Fair weather overnight and into Tuesday.
More scattered tstms expected Tue afternoon. sub-SCA expected
thru the period. Expect higher winds and seas near tstms.

Outlook...

Wednesday...No marine headlines expected. Southerly wind 10-15
knots. Seas around 2 feet.

Thursday...A brief period of SCA conditions possible in the
afternoon with southerly wind 15-20 knots and gusts up to 25 knots.
Seas 3-4 feet.

Friday...SCA conditions possible with southerly sustained winds of
15-20 knots with gusts up to 25 knots. Seas 3-4 feet.

Saturday...SCA conditions possible with southerly sustained winds of
10-15 knots with gusts up to 25 knots. Seas 4-5 feet.

Rip Currents...

There is a LOW risk for the development of dangerous rip currents at
New Jersey and Delaware beaches on Monday. S to SE winds 5 to 10 mph
along with a short period east/southeast swell and breaking waves
around 2 to 3 feet.

Winds will be a bit more onshore on Tuesday, generally E-NE, turning
SE in the afternoon at 5 to 10 mph. A light easterly swell with
breaking waves of 2 to 3 feet will once again be in place. As a
result, there is a LOW risk for the development of dangerous rip
currents at New Jersey and Delaware beaches on Tuesday.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

SYNOPSIS...Brudy
NEAR TERM...OHara
SHORT TERM...Brudy/Henry
LONG TERM...Brudy/Henry
AVIATION...Brudy/OHara/Henry
MARINE...Brudy/OHara/Henry

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Special Weather Statement
National Weather Service Mount Holly NJ
455 PM EDT Mon Jul 24 2023

PAZ060-242130-
Berks PA-
455 PM EDT Mon Jul 24 2023

...A strong thunderstorm will impact portions of south central Berks
County through 530 PM EDT...

At 455 PM EDT, Doppler radar was tracking a strong thunderstorm near
Adamstown, or 8 miles northeast of Ephrata, moving northeast at 10
mph.

HAZARD...Wind gusts up to 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Wyomissing, Sinking Spring, Wernersville, Robesonia, Shillington,
Mohnton, Kenhorst, West Lawn, Whitfield and West Wyomissing.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4040 7613 4030 7593 4024 7603 4032 7616
TIME...MOT...LOC 2055Z 216DEG 10KT 4028 7609

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

AKL