NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Mar 7, 3:36 PM EST, 1 hour 24 minutes earlier.
Area forecast discussion, Mar 7, 3:36 PM EST, 1 hour 24 minutes before
Area Forecast Discussion
National Weather Service Mount Holly NJ
336 PM EST Tue Mar 7 2023
.SYNOPSIS...
Canadian high pressure will build down across the Great Lakes into
the mid-Atlantic through Thursday. Low pressure is forecast to
approach from the Ohio River Valley on Friday. The low is
anticipated to shift to the waters off the Middle Atlantic Coast on
Saturday where it should intensify rapidly before moving farther out
over the ocean. High pressure is expected to follow for Sunday with
another low possibly approaching from the west and southwest on
Monday.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
In the wake of last night's snowfall, at least for northern portions
of our region, skies quickly cleared around mid-morning, giving way
to sunny and windy conditions this afternoon. Winds have been quite
gusty, generally peaking in the 30 to 40 mph range, but locally
higher along some of the exposed mountain ridges near Carbon and
Monroe Counties in Pennsylvania (where a Wind Advisory continues
into the overnight), as well as near High Point, NJ. With another
mid/upper-level shortwave trough passing southward across the
Northeastern U.S. this evening, with a reinforcing shot of cold air
advection, winds will stay strong and gusty right into this evening,
and even remain breezy through the overnight. Some clouds will
increase from north to south this evening associated with this
shortwave, with even a few flurries possible near Mount Pocono, but
otherwise expect tonight to turn out fairly clear in most areas.
As low pressure continues to pull away to the east tonight, well
offshore, and strong Canadian high pressure builds southward across
the Great Lakes and toward the Mid-Atlantic on Wednesday, the
pressure gradient will relax slightly. Still, the lower atmosphere
will remain fairly well-mixed with enough of a surface pressure
gradient for another breezy day. Temperatures will turn out very
similar to Tuesday, with highs mainly in the 40s to around 50. Winds
should be about 5-8 mph lighter and a bit less gusty. Otherwise
expect a sunny and dry day.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
An upper level ridge will build into the area beginning on Wednesday
Night. At the surface, high pressure will nudge its way in from the
northwest. This will result in an overall quiet period until Friday
afternoon. The pressure gradient will slowly weaken, though gusts
will still be around 20 MPH or so through the night. Gusts around 30
MPH or so are possible around the Pocono Plateau. Overnight lows
will be in the mid to upper 20s, with the urban corridor and most of
Delmarva hovering around 30.
Should be a pleasant Thursday as we shake the blustery weather.
Highs will get into the upper 40s/low 50s region wide. Some cloud
cover could hang up in the northern third of the CWA, keeping
temperatures a bit lower. Looking at upper 30s/low 40s around the
southern Poconos/NW NJ. Overnight lows Thursday into Friday will be
very similar to the previous night, with mid to upper 20s for most,
and low 30s around Delmarva and the Philly metro.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
Long-term period looks to be defined as a more active and unsettled
timeframe compared to the middle of this week. Confidence is
increasing in a system impacting the area this weekend with another
potential disturbance moving through early next week. Some wintry
precipitation is possible with at least the first system, though
with the lack of a deep cold airmass, not expecting widespread large
snowfall totals. Currently looks like the best chance for wintry
precipitation/accumulating snow will be from the I-78 corridor
on north for the weekend system. For the early next week system,
guidance is still all over the place with some guidance having
an impactful coastal storm (GEM/ECMWF) and some having no storm
at all (GFS and associated ensemble).
Getting into the day by day forecast, a mid and upper level ridge
axis will move through our area on Friday morning. This will slide
offshore as an upper level trough approaches from the upper Midwest.
Should be quiet for most of Friday, before precipitation begins to
move in later in the day.
A mid-level trough ejecting out of the Central Rockies will move
through the Great Plains and is expected to become a cutoff H5 low
over the central US. The closed low will move east towards our
region, moving offshore by Saturday morning. At the surface, an
area of low pressure will move through the Midwest into western
Pennsylvania, where it is expected to weaken. A secondary low looks
to develop nearby our area. Exact location of the secondary low
remains uncertain. Taking a look at the 12z suite of guidance, the
general trend between the deterministic and ensembles has been a bit
further south with secondary cyclogenesis, having it occur more
towards the Mid-Atlantic Coast. Additionally, it does look like a
bulk of the precipitation will come in during the overnight hours
Friday into Saturday, with temperatures being more favorable for
wintry precipitation. This would open the door for some snowfall for
more of the area, but continue to think that the higher
accumulations will be near/north of I-78 while areas south seeing
mainly rain. A few limiting factors worth mentioning are the
progressive nature of the pattern and the lack of a cold airmass
overall. While confidence is high on a system moving through on
Friday Night/Saturday, confidence on specific impacts, precipitation
type, and any accumulations remains low.
A break in between the two systems looks to comes Saturday night
into Sunday with dry weather as a weak mid-level ridge builds in.
This break will be short-lived as another system may impact the
region early next week.
As mentioned in the opening summary, the forecast beyond Sunday is
highly uncertain. Deterministic guidance has a trough over the
Eastern US early next week, developing a surface low somewhere along
the East Coast. The strength and orientation of the trough will
determine where the low will develop and the eventual storm track.
There is still a wide spread in both the deterministic and ensemble
guidance overall to the point where trends have yet to be even
established. It will bear watching over the next several days.
&&
.AVIATION /21Z TUESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
Tonight...NW winds 15 to 25 kt with gusts 30 to 35 kt at times
continuing through this evening, then easing to 10-15 G20 kt
overnight. Some lower VFR ceilings will attempt to pass by around 02-
07Z from north to south, maybe around 040-070, but may just be SCT
to BKN periodically. High confidence.
Wednesday...Mostly clear skies outside of locally around the
Poconos. VFR conditions and unrestricted VSBY. Still breezy, with NW
winds 10 to 15 kt with gusts around 25 kt in the afternoon. High
confidence.
Outlook...
Wednesday Night...VFR. Northwest winds around 10 kts. High
confidence.
Thursday through Thursday Night...VFR. North/Northwest winds around
10 kts. High confidence.
Friday...Primarily VFR. North/Northeast winds in the morning around
5-10 kts will shift to a more southeast direction in the afternoon,
remaining around 5-10 kts. Rain/Snow showers approach late in the
day. Moderate confidence.
Friday Night...sub-VFR conditions likely. Periods of rain with some
snow mixed in, especially around KRDG/KABE. Brief period of snow
possible at the I-95 terminals. East/Southeast winds around 10 kts.
Moderate confidence.
Saturday through Saturday Night...sub-VFR conditions possible with
rain/snow showers in the morning, potentially lingering into the
early afternoon. North/Northeast wind around 10-15 kts, with gusts
up to 25 kts possible. Low confidence.
Sunday through Sunday Night...VFR. North/Northwest winds around 10
kts. Moderate confidence.
&&
.MARINE...
Strong Canadian high pressure building in across the Great
Lakes and into the mid-Atlantic as low pressure tracks out to
sea will maintain a strong pressure gradient this evening, that
will gradually loosen through mid-week. That will result in
increasing winds across the NJ and DE coastal waters and DE Bay,
with Gale Warnings going into effect and continuing at least
through this evening. Winds appear to ease slightly north of
Atlantic City overnight, then gradually drop off further into
Wednesday. That will maintain Small Craft Advisory conditions
through Wednesday afternoon for much of our coastal waters, with
seas around 3 to 5 feet lingering.
Outlook...
Wednesday Night...SCA conditions possible. Northwest winds around 15-
20 kts, with gusts nearing 25 kts. Seas 3 to 5 feet.
Thursday through Thursday Night...No marine headlines anticipated.
North/Northwest winds around 10-15 kts. Seas 2 to 4 feet.
Friday...No marine headlines anticipated. Northerly winds will shift
to a more south/southeasterly direction. Wind speeds around 10 kts.
Seas 2 to 4 feet.
Friday Night...SCA conditions possible. Southeasterly winds around
10-15 kts gusting to 20 kts. Seas building, getting near 5 feet.
Saturday through Saturday Night...SCA conditions likely with
possible gales Saturday Night. Winds become northwesterly around 20-
25 kts with gusts getting close to 35 kts at night. Seas 4 to 7 feet.
Sunday through Sunday Night...SCA conditions likely. Northerly winds
around 10-20 kts, with gusts nearing 25 kts. Seas 4 to 6 feet.
&&
.FIRE WEATHER...
An SPS continues for elevated fire weather conditions over much of
the Delmarva Peninsula. Additionally, RH was lower than forecast
this afternoon around the NJ Pine Barrens, down to around 25 to 30
percent. There was a wildfire start there, and 25 to 35 mph ocnl 40
mph wind gusts will continue into early evening. Breezy conditions
will remain overnight even as winds ease somewhat, and that will
keep RH recoveries modest, around 60 to 65 percent. Heading into
Wednesday, that will set the stage for drier fine fuel moisture.
However, dewpoints are expected to come up a little bit, with
afternoon RH about 10 percent higher than Tuesday; around 35 to 40
percent at minimum. That will combine with less windy, but still
breezy conditions, with some gusts at least over 25 mph likely much
of the day. Will likely need an SPS for elevated fire weather
conditions for much of our region, but will reassess overnight and
first thing in the morning.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Wind Advisory until 6 AM EST Wednesday for PAZ054-055.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 4 PM EST this afternoon for ANZ430-
431-450>455.
Gale Warning until 7 AM EST Wednesday for ANZ430-431-453>455.
Gale Warning until 1 AM EST Wednesday for ANZ450>452.
&&
SYNOPSIS...Hoeflich/Iovino
NEAR TERM...Dodd
SHORT TERM...Hoeflich
LONG TERM...Hoeflich
AVIATION...Dodd/Hoeflich
MARINE...Dodd/Hoeflich
FIRE WEATHER...Dodd