Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 151550

Area Forecast Discussion
National Weather Service Mount Holly NJ
1150 AM EDT Thu Mar 15 2018

Low pressure will remain over the Canadian Maritimes through
Saturday, then weaken as it moves eastward. Meanwhile, a cold front
will move through the region tonight and be followed by high
pressure which will dominate our weather Friday through Friday
night. A weak low pressure system will pass by to the south Saturday
followed by more high pressure for Sunday. Low pressure in the
Central Plains later Sunday and Monday tracks eastward, and this may
result in another coastal storm in the east by next Tuesday into


Snow showers over central PA continue to track east and will be
moving into western portions of the forecast area early this
afternoon. Temperatures, however, are above freezing, and will
continue to warm through the 40s for most of southeast PA and
most of NJ, so expecting a mix of rain and/or snow showers. The
southern Poconos, Carbon and Monroe counties, however, will
remain below freezing, so locally moderate snow is possible
there with accumulations of up to 2". Elsewhere, accumulating
snow is not expected. Bumped up PoPs a bit, but think by the
time the showers make it through NJ, it will not be until early
evening, and the loss of diurnal heating will allow the showers
to dissipate, and they will not be as numerous as they will be
to the west.


The cold front will quickly move through the region early this
evening. The potential for convective showers will linger behind the
front through at least the first half of the evening (6-9 PM),
possibly later in the southern Poconos where lake-effect enhancement
will prolong the threat of snow showers into the overnight. The
higher elevations in northern Carbon and Monroe Counties could
receive an additional 1-4" inches of snow (with most of it falling
in a 6-hr period from about 4-10 PM), which are the same areas that
received 1" to locally as high as 7.5" of snow yesterday.

A pressure surge and CAA in wake of the cold front should result in
gusty W-NW winds tonight. Models generally agree that the strongest
winds will occur during the evening across SE PA, S NJ and Delmarva
where gusts to around 35 mph are possible.

Low temperatures range from the around 20 degrees in the southern
Poconos to around 30 degrees in the urban I-95 corridor and coastal


Friday through Saturday night...

Fairly quiet for this part of the forecast as upper trough remains
in place over eastern Canada keeping broad cyclonic flow over the

To start the period, strong NW flow will remain in place Friday as
strong pressure gradient continues between low pressure over
Atlantic Canada and high pressure over the Great Lakes. Expect winds
generally gusting 25 to 30 mph during the day. Temperatures will
also be cooler with temperatures near the top of the mixed layer
near 850 mb around -10 to -12 C suggesting max Temps generally
in the upper 30s to low 40s and even colder in the southern
Poconos and NW NJ (upper 20s to mid 30s) where there could be
some lingering stray snow showers. Otherwise, expect a mix of
sun and clouds due to diurnal Cu with the most sun in the south
and clouds in the north.

For Friday night, winds ease as pressure gradient relaxes and also
due to loss of heating. In fact weak surface ridging will move in
just to the south so expect clearing skies to lead to fairly good
radiational cooling. Lows by Saturday morning will be generally in
the 20s except upper teens across the southern Poconos.

For Saturday, upper level low and associated surface low remain in
place over Atlantic Canada keeping a broad cyclonic NW flow over the
area. This should suppress a southern stream wave moving in from the
west mainly to our south but expect skies to become mainly cloudy by
the afternoon across the southern Delmarva with the northern edge of
the system possibly just brushing this area with a little light
rain. Chances for this are low so only have slight chance POPs
mentioned. Otherwise, expect sunshine farther north which will be
filtered at times through mid and high clouds. Winds will be lighter
with moderating temperatures and generally expect highs in the 40s
except 30s across the southern Poconos.

For Saturday night, system to the south moves out with mainly clear
and cool conditions. Lows range from the upper teens to low 20s
north to the upper 20s to low 30s south.

Sunday through Wednesday...

High pressure re-establishes itself over the area for Sunday
bringing sunshine and relatively light winds with highs mainly in
the 40s, except 30s over the southern Poconos. This high will weaken
and move off to the east Monday as clouds begin to increase ahead of
the next system. At this time, forecast models are still indicating
the potential of for a storm on the east coast beginning next Monday
night into Tuesday however there remain many uncertainties. This
system will be driven by upper level energy currently along with
west coast that is progged to move across the country over the
weekend into early next week. However there is uncertainty regarding
whether this energy comes across as one main piece or fractures into
several weaker waves and this will have a bearing on the storms
evolution, strength, and track. Also, if the primary low remains
dominant and tracks north into the Ohio Valley this would mean
warmer temperatures and mainly rain while secondary development off
the coast would favor colder temperatures with a better chance for
snow. This all said, current forecast does not stray much from
previous forecast due to this uncertainty although we did bring
likely POPs for rain/snow a little farther north into the I-95
corridor for Tuesday. The latest guidance suggests the upper trough
associated with this system may close off to the south by later next
Wednesday so we keep chances for rain/snow showers in the forecast
through midweek.


The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

This afternoon and evening...Predominately VFR. A PROB30 group
was included at all TAF sites except ACY from about 18Z-00Z with
scattered coverage of showers anticipated. Brief/localized MVFR
CIGs possible with these showers. Vsby restrictions will also
be a possibility at ABE and RDG, where it will be cold enough to
allow for rain at the onset to change to snow. A wind shift
from SW to W-NW is expected late this afternoon-early this
evening in conjunction with a cold fropa. Winds will become
gusty, especially across southern terminals (PHL-ILG-MIV-ACY)
this evening, where peak gusts near 30 kt are forecast.

Late tonight...VFR expected. W-NW winds should gradually weaken.


Friday...VFR. NW winds generally around 15 to 20 gusting up to
30 knots. High confidence.

Friday night...VFR with diminishing winds. High confidence

Saturday through Sunday...VFR overall. High confidence.

Monday...Clouds increase especially late day and at night, with
possible MVFR/IFR conditions developing overnight if
precipitation develops. Moderate confidence.


Wind gusts on the waters range from 25-30 kt today, so went
ahead and issued a Small Craft Advisory for today and maintained
the Gale Warning that is in effect for tonight for DE Bay and
southern NJ ocean and DE ocean waters. SCA remains in effect for
northern NJ ocean waters.

The greatest risk for gales will be focus around a 5 hr period
between approximately 10 PM and 3 AM.


Friday...Strong SCA to marginal Gale conditions with NW winds
generally gusting to near 30 knots with gusts to 35 knots
possible across the northern waters. These winds begin to
diminish Friday night.

Saturday and Sunday...Diminishing conditions, therefore mainly sub-
Small Craft Advisory criteria.

Monday...The conditions should be below Small Craft Advisory
criteria, although winds should start to increase from the east-
northeast later Monday.


MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ430-
     Gale Warning from 6 PM this evening to 6 AM EDT Friday for
     Small Craft Advisory until 6 AM EDT Friday for ANZ450-451.


Near Term...Klein/MPS
Short Term...Klein
Long Term...Fitzsimmons
Marine...Fitzsimmons/Klein/MPS is the U.S. government's official web portal to all federal, state and local government web resources and services.