Special Weather Statement, NWS Philadelphia/Mount Holly

Area Forecast Discussion
National Weather Service Mount Holly NJ
955 PM EDT Sun Aug 21 2022

.SYNOPSIS...
An area of low pressure will slowly meander is way our of the
Ohio River Valley and into the eastern Great Lakes tonight,
before moving across Pennsylvania and New York Monday into
Monday night. It will then move across New England Tuesday into
Tuesday night and into the Canadian Maritimes Wednesday.
Meanwhile, a warm front will lift across the Mid Atlantic region
tonight, before a cold front slowly moves across the eastern
seaboard Monday through Tuesday. High pressure weakens as it
moves into the area by mid week, before another cold front
approaches later Thursday into Friday.

&&

.NEAR TERM /THROUGH MONDAY/...
The forecast remains on general track as of the evening update.
Showers and storms are now gathering and expanding across our
southwestern zones and just southwest of our area and expanding
northeastward. PWATs continue creeping up as well.

This is the developing main show, which will envelop our area
overnight and into the morning hours as a surface low slowly
progresses through the Great Lakes region. An associated warm
front will lift north, entering our area just after midnight.
This will result in a morning round of showers and
thunderstorms. The main concern is heavy rain as PWATs will be
approaching 2 inches, however storms should be moving at a
decent clip through our region. Since this looks to be a multi-
round event though, if similar areas see convection, flooding
could be an issue. Instability will be larger than today, with
CAPE values approaching 1000-2000 J/KG. However, similar to
today, shear will be minimal, so while a few strong to severe
storms are possible, flooding will be the primary hazard.
Thinking the heaviest thunderstorms are out of the region by the
end of Monday morning.

Monday early afternoon will feature some scattered lingering
showers. As the cold front approaches and forcing gets stronger,
shower/thunderstorm coverage should increase late
afternoon/early evening Monday. Destabilization should be
limited as cloud cover will persist through the day, and
coverage will be less compared to the morning. However,
scattered storms could produce a heavy downpour and brief period
of gusty winds. Best chance to see this second round of
convection will be from the I-95 corridor and points north and
west, though all locations were included in Chc PoPs at a
minimum. Temperatures should be held down a bit with the
abundant cloud cover. Thinking upper 70s/low 80s through the
region.

In terms of total rainfall, still looking at a general 0.5-1.5"
of rain, with lower end totals around the Delmarva peninsula
and SE NJ, and higher end totals in the Lehigh Valley, Poconos
and NW NJ. Locally higher amounts of rain are possible,
primarily north and west of Philadelphia.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
An area of low pressure will continue to slowly meander across
Pennsylvania and New York Monday night, before drifting into New
England Tuesday into Tuesday night, then finally shifting into
the Canadian Maritimes Wednesday. Meanwhile, mid level troughing
will remain just to the west of the area Monday night through
Tuesday, with the Mid Atlantic region within a southwest flow
aloft. Several short wave/vorticity impulses are forecast to
move across the area, which will combine with the slow moving
frontal boundary and some instability to lead to at least
scattered showers and thunderstorms across the area. The highest
probabilities will be tied to the short waves, which are most
likely Monday evening, then during the afternoon Tuesday. While
widespread severe weather is not anticipated, a few strong
storms could be possible, especially Tuesday afternoon. Also, PW
values remain 1.5-1.75 inches, so some locally heavy rainfall
will be possible.

The cold front shifts offshore Tuesday night before high
pressure build to our west on Wednesday. A dry forecast is
expected to return Tuesday night, but an isolated sea-breeze
shower is possible in southern NJ or DE on Wednesday afternoon.
Temperatures will remain above normal.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Guidance for the general upper level pattern and its evolution
during the duration of the long range period continues to convey
large spread and uncertainty in exact timing and strength of
features. A meteorological col situation looks to setup prior to
the start of the long range period and should still be in place
by at least the Friday night time frame. In terms of this col
situation ridging will be located to our northwest and northeast
and upper level low pressure will be located well north while
to start a weak or dissipating trough is located over the
Eastern CONUS. In a meteorological col situation the general
upper level pattern is usually slow to change and often guidance
and ensembles have difficulty projecting pattern evolution and
strength change of upper level features. Eventually however the
col will have to give and will be no longer. Guidance indicates
majority breakdown of the col by Saturday night which gives way
for the ridge that was to the northwest to slide east. Sunday
could see that ridge to either our north or northeast with some
of the ensembles building the ridge for the Sunday time frame.
Confidence is high that the col will set up during this week but
confidence in the timing and exact location of the col
breakdown is lower. There is at least medium confidence that the
col will breakdown down sometime before the end of period and
there is high confidence that the ridge will slide eastward
after its breakdown. How strong that ridge will be and the
timing of its placement remains to be seen.

At the surface level the upper level situation favors high
pressure to mainly be dominate for most of the long range period
with temperatures remaining mainly above average. Surface high
pressure should remain over the region Wednesday night into
Thursday morning. A cold front looks to approach from the
northwest Friday and make way through the region possibly by
Saturday morning. Guidance indicates little forcing with this
front but the chance of showers cannot be ruled out for now.
High pressure builds in after the frontal passage and should
remain over the region into Sunday. Guidance indicates a surface
low developing to the south Sunday but it is too early to have
any confidence in the development of this low.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...As showers (and a few embedded storms) become more
widespread, ceilings should lower to MVFR and even IFR for most
locations, and have already begun to do so at southern
terminals. Have VCTS and/or tempo groups for TSRA for all
terminals overnight. Following the initial round of morning
showers and thunderstorms, ceilings look to go down to IFR
levels for all terminals.

Monday...A break looks likely just after sunrise, though some
lingering showers will persist through the morning. IFR ceilings
look to lift to MVFR toward midday, however some afternoon
showers and thunderstorms likely fire up again. Generally east
to southeast winds less than 10 kt. Moderate confidence on the
overall pattern and lower confidence on timing details.

Monday night...Showers and thunderstorms in the evening likely
diminish rapidly overnight, with at least a period of VFR
conditions likely. However, with enough breaks in the clouds and
plenty of low-level moisture present, the risk of low clouds and
fog resulting in IFR conditions exists later at night. Low
confidence.

Outlook...

Monday night...At least a chance of showers in the evening
hours, with the possibility of sub-VFR conditions. Southeast
winds around 5 knots become light and variable overnight.
Moderate confidence.

Tuesday...There is at least a chance of showers in the
afternoon, with the possibility of sub-VFR conditions through
the day. West to southwest winds 5-10 knots. Moderate
confidence.

Tuesday night...Showers taper off during the evening. Some
scattered MVFR ceilings are possible. West to southwest wind
early, become northwest overnight with speeds around 5 knots or
less. Moderate confidence.

Wednesday-Wednesday night...Generally VFR. West to northwest
winds 5- 10 knots become light and variable overnight. Moderate
confidence.

Thursday-Friday...Generally VFR. Slight chance of showers which
could occasionally lead to lower conditions. Winds will vary
between southwest to northwest 5-10 knots during the day, then
be light and variable overnight. Moderate confidence.

&&

.MARINE...
Through Tonight... Sub-Advisory conditions with no marine
headlines expected. Southeast winds around 10 kts. Seas 2 to 3
feet. Showers and thunderstorms likely late tonight/early
tomorrow morning.

Monday...Sub-advisory conditions expected. Southerly winds
around 10- 15 kts with gusts up to 20 kts. Seas 2 to 3 feet.
Showers and thunderstorms at times through the day.

Outlook...

Monday night-Friday...Conditions will remain below advisory
levels through the period. Winds will periodically gust around
20 knots, and seas may approach 4 feet at times. There is a
chance of showers and thunderstorms Monday evening into Tuesday,
which could produce locally higher winds and waves.

Rip Currents...

For Monday, a southerly wind around 10 kts and wave heights of
1-3 feet with southerly swell of 2 feet on a period of 4 seconds
should result in a LOW risk for the formation of dangerous rip
currents.

For Tuesday, a southwesterly wind around 10 kts and wave
heights of 2-3 feet with southerly swell of 2 feet on a period
of 5 seconds should result in a LOW risk for the formation of
dangerous rip currents.

&&

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

&&

SYNOPSIS...Robertson/RCM
NEAR TERM...Hoeflich/RCM
SHORT TERM...Robertson/RCM
LONG TERM...Wunderlin
AVIATION...Hoeflich/Robertson/RCM
MARINE...Hoeflich/Robertson/RCM

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Special Weather Statement
National Weather Service Mount Holly NJ
1112 PM EDT Sun Aug 21 2022

MDZ019-020-220345-
Talbot MD-Caroline MD-
1112 PM EDT Sun Aug 21 2022

...A strong thunderstorm will impact portions of eastern Talbot and
southern Caroline Counties through 1145 PM EDT...

At 1111 PM EDT, Doppler radar was tracking a strong thunderstorm over
Trappe, or near Cambridge, moving northeast at 30 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...
Easton, Federalsburg, Trappe, Preston, Agner, Matthews, Choptank,
Tanyard, Harmony, Hambleton, Windyhill and Cordova.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 3859 7606 3860 7606 3863 7608 3864 7615
      3866 7616 3890 7605 3875 7571 3864 7571
      3869 7577 3868 7580 3870 7580 3871 7584
      3868 7593 3863 7598 3860 7599 3857 7603
TIME...MOT...LOC 0311Z 208DEG 24KT 3865 7602

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

SFJ