Winter Weather Advisory 5, NWS Philadelphia/Mount Holly

Area Forecast Discussion
National Weather Service Mount Holly NJ
1253 PM EST Sun Feb 26 2023

.SYNOPSIS...
Weak low pressure tracks well north of our area today, however a
weak cold front settles into our area. High pressure then extends
down into our area tonight into Monday. Strong low pressure tracks
into the Great Lakes later Monday and weakens while another low
develops off the northern Mid-Atlantic coast. This entire system
this lifts to our north and east late Monday night and Tuesday. Weak
high pressure briefly arrives Wednesday, then another system arrives
Wednesday night and Thursday. A potentially strong system may
then arrive on Friday, followed by high pressure Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Clouds and fog are slow to dissipate. As temperatures rise, fog
will dissipate by late morning, and clouds will lift through
the morning before scattering out late this afternoon.

A weak clipper will pass across New York State this afternoon,
as surface high pressure sits off the coast of the Outer Banks.
This will welcome the return of a southwesterly pressure
gradient which will tighten through the afternoon. Not expecting
too much in the way of gusty conditions, although a few
isolated gusts up to 25mph are possible especially at higher
elevations and down toward the coast. With southwesterly flow at
the surface and warm air flowing north, our afternoon highs
will reach the upper 40s to low 50s.

A weak cold front associated with clipper system will drop south
this evening, but with a moisture starved environment, no
precipitation will occur. Winds will veer to northwesterly behind
the front, then diminish overnight. Lows will range from the mid 20s
to low 30s, however a few locales may fall into the upper teens to
low 20s but only if winds become calm, allowing radiational cooling
to occur under clear skies.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Summary...Accumulating snow later Monday and Monday night for the
northern areas (mainly rain elsewhere), then gradually improving
conditions on Tuesday.

A complex setup is forecast to be in place Monday into Tuesday. An
upper-level trough tracking up the Ohio Valley Monday is forecast to
deamplify as it moves across the Northeast. Despite this, new
surface low development is expected to occur off the northern Mid-
Atlantic coast Monday night. As this occurs, the parent surface low
across the eastern Great Lakes is forecast to weaken as it moves
north of Lake Ontario Tuesday morning. This setup favors a zone of
strong ascent which results in a widespread precipitation event. The
model guidance is slowing the arrival of the precipitation Monday,
therefore we slowed down the PoP increase quite a bit during the
day. Clouds are expected to quickly increase and thicken Monday
morning.

While much of the area is expected to see primarily rain from this
with rainfall amounts mainly in the 0.50-0.75 inch range, areas
along the I-78 corridor should see some snow/sleet (locally some
freezing rain in parts of Berks County into the Lehigh Valley and
southern Poconos). It is the I-80 corridor that is expected to have
more of an accumulating snow event. There will be warm air advection
partially driving the forcing for ascent, however farther north and
west this looks to weaken as the coastal low develops and starts to
take over. The model forecast soundings for the Pocono region into
northwestern New Jersey indicate that some warming occurs in a
narrow layer however precipitation cools this. Therefore, snow
should occur for the I-80 corridor for much of the event although
some sleet should mix in for parts of the area. South of there,
there should be a zone of some mixed precipitation to even a
transition to rain. This will likely hold snow accumulations down.

Since the primary low into the eastern Great Lakes weakens with
time, the warm air advection becomes more reduced and this should
favor less mixing or a changeover to non-snow in much of the
southern Poconos into northwestern Jersey. This could be tricky
though as a bit more warming would introduce more mixing farther
north and lower the snowfall totals. For the I-80 corridor, the
highest snow totals are here with 3-5 inches currently forecast, and
the snow intensity may become heavier for a time as a northwest to
southeast ribbon of frontogenetic forcing moves through. The current
thinking is that this is a solid advisory event for the I-80
corridor and therefore we opted to hold off on a Winter Storm Watch.
For Berks County, the Lehigh Valley to some areas northeastward may
also need an advisory especially if some freezing rain ends up
occurring.

The precipitation should start ending from the southwest later
Monday night as the coastal low consolidates and starts to move
away. Precipitation should tend to become lighter across the
northern areas later Monday night but will hold on longer Tuesday
morning before ending. As we go through Tuesday, conditions are
expected to improve as the storm system moves farther to our north
and east. May hold onto the cloud cover for much of the day,
especially across the northern areas. Tuesday afternoon temperatures
should rebound nicely, mostly for the southern areas where at least
some clearing should occur sooner. A mostly clear sky then Tuesday
night with temperatures dropping back into the 20s and 30s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Summary...Mild through Thursday, then cooler overall into the
weekend. Low pressure and a front arrives Thursday, then another
storm, potentially strong, may arrive Friday however there is
uncertainty with its evolution.

Synoptic Overview...Some ridging slides over our region Wednesday.
This places surface high pressure over our area to start Wednesday
before it shifts eastward. An upper-level trough from the Plains to
the Midwest will gradually shift eastward Wednesday night into
Thursday, with a stronger part of this trough sliding across the
southwestern U.S. Surface low pressure tracks along a baroclinic
zone which runs up across the Great Lakes into Thursday, with a cold
front moving through our area during Thursday. A more potent trough
will be ejecting eastward from the Southwest U.S. later Thursday.
While the guidance differs on the details with the associated
surface low, it does appear that some impacts will occur in our area
during the Friday timeframe. Overall, there remains the potential
for a strong storm system to track from the Gulf Coast States to the
Mid-Atlantic region Thursday through Friday. High pressure should
then build in from the west during Saturday in the wake of the storm.

For Wednesday...An active flow pattern continues, with surface high
pressure over the area to start Wednesday quickly shifting offshore
during the day. As this occurs, an upper-level trough across the
Plains will start to shift eastward and support surface low
pressure. This will pull a developing warm front northward and with
increasing southerly flow between this system and the offshore high,
warm air advection will increase. The daytime should remain dry
however clouds will be on the increase. Some precipitation, mainly
in the form of rain, should start to develop Wednesday night as
increasing ascent overspreads the area. This timing carries some
uncertainty with it though as it will depend on how quickly the
trough and surface low to our west shifts eastward. Temperatures
during the day are forecast to get into the low to mid 50s for much
of the area, with even around 60 degrees across parts of Delmarva.
Given the southerly flow and increasing warm air advection,
temperatures at night will be on the much milder side with many
places only falling back into the 40s.

For Thursday...An initial upper-level trough is forecast to arrive
with surface low pressure tracking just to our west and north. This
will pull a cold front across our area in the morning, then a
secondary cold front should near our area Thursday night. There will
be enough lift and moisture with this system to result in showers or
a period of rain. Much of our area should be in the warm sector to
start, however its northern extent may be halted some as the parent
storm may be undergoing an occlusion. While some cooling follows the
system, it looks to be on the weaker side with the lower levels
remaining mild for a longer period of time. As a result, a rather
mild day is expected especially for the coastal plain where low to
mid 60s are currently forecast. It then turns colder Thursday night.
While it could dry out, this is less certainty as it will depend on
what is happening well to our southwest with the next system.

For Friday...Increased uncertainty during this time frame as our
weather will be determined by a strong upper-level trough making its
way toward the East Coast. At least some of the deterministic
guidance is showing a strong surface low running up across the Mid-
Atlantic region, however this track is much less certain. While the
ensemble guidance does show this storm, there is variability in this
guidance which results in lowered confidence. If a storm does occur,
it may tend to be quick moving given the continued active flow it is
embedded in. Given the uncertainty with the details including
surface temperatures and vertical thermal profiles, kept the
precipitation types more simplified and the flavor of the forecast
follows closely to the National Blend of Models (NBM).

For Saturday...The storm should be well to our northeast to start
Saturday with surface high pressure building in from the west. The
flow aloft is still forecast to be active and from the west-
northwest, which could send some additonal ripples of energy our
way. For now, kept the forecast dry as we look to be between systems
with high pressure in control. High temperatures may tend to be a
bit below average.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

As of 18z...Skies are rapidly clearing across the region. What
remains of the low level cloud deck from this morning continues
to lift and dissipate. Not much in way of cloud cover can be
seen on satellite as of 18z. However, most sites are still
carrying a broken layer above 2kft. Expecting all sites to give
way to VFR conditions for the rest of the day shortly. Winds
will be out of the SW at 10 to 15 kts today with gusts around 20
kts. High confidence.

Sunday night...VFR through the period. Winds will drop off
while veering to the northwest this evening, and remain NW/NNW
around 3-5 kt overnight. High confidence.

Outlook...

Monday...MVFR to possibly IFR conditions in the afternoon, then IFR
much more likely at night with rain. Some snow or a wintry mix for a
time at KRDG and KABE. The precipitation will start to end from
southwest to northeast later Monday night. East-northeast winds 5-10
knots becoming east-southeast 10-15 knots, then becoming northeast
to north 10 knots or less overnight. Low confidence with the details.

Tuesday...Gradual improvement to VFR during the day. Northerly winds
around 10 knots, becoming west-northwest. Moderate confidence.

Wednesday...VFR. East-northeast winds around 10 knots, becoming
southeast. Moderate confidence.

Wednesday night and Thursday...Sub-VFR conditions probable with
rain. Southeast to south winds 5-10 knots, becoming southwest to
west-northwest 10-15 knots Thursday and Thursday night. Low
confidence.

&&

.MARINE...
Buoy 44065 is starting to gust to 23 kt. With clouds scattering
out, and the pressure gradient tightening over the waters this
afternoon, think wind gusts will increase a bit further for this
afternoon. Will go ahead and issue a Small Craft Advisory for
ANZ450-451 until 7 pm. Winds should diminish fairly quickly
after sunset.

Otherwise, winds will increase out of the SW at 10-15kt with
gusts up to 20kt. Seas of 2-4ft.

Tonight...Following the passage of cold front, winds out of the SW-W
will become NW-N during the evening and overnight period. Widespread
area of sustained winds of 15-20kt are likely for all marine zones.
Will have to closely watch the zones off of Monmouth and Ocean
County NJ as a few spots offshore may gust up to 25kt. Due to
localized areas and relatively low confidence if these gusts will
occur, we not issuing a Small Craft Advisory with this update for
these zones. Seas of 3-4ft.

Outlook...

Monday...Small Craft Advisory conditions develop late in the
afternoon and continue at night. A period of low-end gale force wind
gusts possible mainly across the northern New Jersey waters, and a
Gale Watch has been issued for there.

Tuesday...A period of Small Craft Advisory conditions probable in
the morning, then conditions should gradually improve through the
afternoon.

Wednesday...The conditions should mostly be below Small Craft
Advisory criteria.

Wednesday night through Thursday...Small Craft Advisory conditions
probable.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ450-
     451.
     Gale Watch from Monday evening through late Monday night for
     ANZ450-451.

&&

SYNOPSIS...Gorse
NEAR TERM...Dodd/DeSilva/MPS
SHORT TERM...Gorse
LONG TERM...Gorse
AVIATION...Dodd/Gorse/Wunderlin
MARINE...Dodd/DeSilva/Gorse

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
916 AM EST SUN FEB 26 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0700 AM     SNOW             1 ESE CANADENSIS        41.19N 75.24W
02/26/2023  M0.1 INCH        MONROE             PA   CO-OP OBSERVER

            CO-OP OBSERVER STATION CNDP1 CANADENSIS.

&&

STAARMANN

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1025 AM EST SUN FEB 26 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0400 PM     SNOW             2 E NASSAU              38.72N 75.12W
02/25/2023  E1.0 INCH        SUSSEX             DE   PUBLIC

            RELAYED ESTIMATED REPORT OF 1 TO 2 INCHES OF
            SNOW ABOUT 2 MILES INLAND FROM REHOBOTH
            BEACH. ACCUMULATION WAS MAINLY ON THE GRASS,
            BUT ALSO ON THE CARS AND BRIEFLY ON
            PAVEMENT.

&&

STAARMANN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1027 AM EST SUN FEB 26 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0400 PM     SNOW             REHOBOTH BEACH          38.72N 75.08W
02/25/2023  E0.3 INCH        SUSSEX             DE   BROADCAST MEDIA

            RELAYED REPORT VIA BROADCAST MEDIA. TIME
            LAPSE VIDEO SHOWING A LIGHT COATING OF SNOW
            ACCUMULATING ON ELEVATED SURFACES, INCLUDING
            THE BOARDWALK IN REHOBOTH BEACH.

&&

STAARMANN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1258 PM EST SUN FEB 26 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0700 PM     SNOW             ATLANTIC CITY INTERNATI 39.45N 74.57W
02/25/2023  M0.1 INCH        ATLANTIC           NJ   ASOS

&&

STAARMANN