Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 191724

Area Forecast Discussion
National Weather Service Mount Holly NJ
1224 PM EST Sun Nov 19 2017

Low pressure over upstate New York will lift northeast into the
Saint Lawrence Valley today. The attendant cold front will move
through the Mid Atlantic early this morning. High pressure will
build in from the south and west tonight into Monday before moving
off the Southeast coast on Tuesday. A cold front is expected to pass
through the region late Tuesday night or Wednesday morning. High
pressure builds back into the area for Thanksgiving. The high will
eventually weaken and move offshore late in the week as a cold front
approaches from the Midwest. The front will likely move through the
Mid Atlantic on Saturday.



Blustery conditions will continue through today as the brisk
west to northwest wind has set up across the area. Winds
continue to gust 35-45 mph, with occasional gusts up to 50 mph.
The Wind Advisory continues across the area.

Temperatures will not rise much more today, and will likely
begin falling through the remainder of the afternoon for most
areas. Precipitation has ended for now across the area, but a
few showers associated with some lake effect streamers may make
their way into the the Poconos later this afternoon.


Main question tonight is the potential for some snow showers in the
Poconos. With a strongly mixed boundary layer and saturation around
900-850 mb, there are indications that snow showers will develop
periodically to the northwest, occasionally progressing into the
southern Poconos. The best time window for this looks to be late
this evening and overnight as the deep-layer flow becomes more
northwesterly (more favorable fetch for lake-effect "streamers").
Additionally, the main vort max associated with today`s system will
be moving through Sunday night, which will supply additional lift
and cold air aloft to aid in the development of a shallow (nearly)
dry-adiabatic boundary layer in the post-frontal environment. Have
kept and even prolonged slight-chances or chances of snow showers in
this region, with potential for snow squalls given the strong low-
level wind field and favorable low-level thermodynamic profile.

Meanwhile, temperatures will turn colder across the area, though the
bottom will not fall out given the continued elevated winds (though
much lighter than during the day). Current forecast is a mix of
MAV/MET/ECS MOS, which are in reasonable agreement, and features
temperatures generally a few degrees below seasonal averages.


A rather tranquil and predominately cool weather pattern is in
store for next week.

Monday and Monday night... High pressure builds to our south across
the Southeast states on Monday. Westerly winds will still be breezy
(gusts 20-30 mph) owing a tight pressure gradient to the north of
the surface high but not nearly as strong as today. CAA thermal
pattern in the low levels transitions to neutral Monday morning and
eventually even to a WAA pattern once the cold pool progress
downstream of the area late afternoon and night. Dry and cool
conditions can be expected with high temps 6-9F below normal and
lows 3-6 below normal.

Tuesday... High pressure moves off the eastern seaboard. Southerly
return flow around the high will draw milder air into the region.
Highs return to near normal. Winds will once again be breezy,
especially during peak afternoon heating with gusts 20-30 mph.

Tuesday night and Wednesday... A cold front will approach from the
Tuesday evening before moving through the forecast area late Tuesday
night into early Wednesday morning. Models continue to hint at a
band of rain developing over the Mid-Atlantic region Tuesday night
in response to frontogenetical lift that occurs in between a
northern stream shortwave trough and a southern stream disturbance
that is tracking off the Southeast coast. These systems do not
appear to phase in time to bring more significant rains to our area,
instead provide us with a glancing blow. PoPs and QPF increase from
northwest to southeast across the forecast area with models in
agreement that the better dynamics pass near the coast. Rain is
forecast to end from west to east during the first half of the
morning as drier air arrives in wake of fropa. Similar to what
happens today, temperatures initially in the 40s and 50s will
struggle to rise much during the day Wednesday as CAA offsets
daytime heating.

Wednesday night through Friday...Quiet weather is in store for
Thanksgiving with high pressure building overhead and even into
Black Friday when the high starts to retreat offshore. Below normal
temperatures return with highs in the lower to mid 40s on Thursday
and mid 40s (N/W of the Fall Line) to lower 50s (S/E of
Philadelphia) Friday.

Friday night and Saturday...A cold front will approach from the
Midwest Friday night and then move through the region sometime on
Saturday. The setup with this system is similar to the predecessor
one Tuesday night/Wednesday morning system where both northern and
southern stream systems fail to phase in time to produce a
significant rainfall event across the forecast area. The airmass
moderates to within a few degrees of climo in pre-frontal warm
sector on Saturday before colder air moves back into the region
later in the weekend.


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

Today...VFR conditions will prevail through today. Gust winds
30-40 knots for much of the remainder of the day, although winds
will begin to diminish some later this afternoon. High

Tonight...VFR with west winds slowly diminishing to around 10
kts after midnight. Gusts to 25 kts or so possible through the
evening hours. Confidence above average.


Monday through Tuesday...VFR. W winds 10-15 kt with gusts around 25
kt on Monday become SW and weaken to under 10 kt Monday night. SW
winds increase on Tuesday to around 10 kt with gusts to 20 kt during
the afternoon. Forecast confidence:  High.

Tuesday night and Wednesday...Mainly VFR. However, the chance for
rain increases late Tuesday night into early Wednesday morning,
especially closer to the coast. Cannot rule out MVFR CIGs if
steadier rain develops along and especially east of I-95 terminals
between 06-12Z Wednesday. Wind shift from SW to NW will in wake of
cold fropa early Wednesday. NW winds gusts to around kt on
Wednesday. Forecast confidence: Medium overall; low for MVFR CIGs.

Wednesday night and Thursday...VFR. NW winds gradually diminishing.
A storm system is currently expected to remain offshore. Forecast
confidence: Medium to High.


Gale conditions are generally occurring across the waters at this
time, Winds 40-45 kts are likely during this time window. Very
choppy/erratic seas are likely through the day.


Monday and Monday night...SCA conditions likely with NW winds
gusting to 25-30 KT around daybreak, gradually decreasing
throughout the day. Seas in the coastal waters will also
subside, starting out at 4-5 ft in the morning, then becoming
2-4 ft by late afternoon.

Monday night...No marine headlines anticipated. NW winds drop below
25 kt and seas decrease to 2-3 ft.

Tuesday and Tuesday night...SCA likely beginning late morning and
continuing through the evening. SW winds increase to 15-20 kt with
gusts 25-30 kt gusts. Seas in the ocean waters are forecast to peak
in the 5-6 ft range by early Tuesday evening. Winds and seas
diminish overnight.


A Low Water Advisory was issued for the Delaware Bay north of a
line from East Point, NJ to Slaughter Beach, DE (ANZ430 marine
zone). This was based on the latest Total Water Level forecast
of around -2 ft MLLW near high tide late this afternoon-early
evening. A more westerly wind direction (vs northwesterly) of
the strong winds should limit the blow out potential in the
tidal portion of the Delaware River (including Philadelphia)
this evening.


PA...Wind Advisory until 4 PM EST this afternoon for PAZ054-055-
NJ...Wind Advisory until 4 PM EST this afternoon for NJZ001-007>010-
DE...Wind Advisory until 4 PM EST this afternoon for DEZ001>004.
MD...Wind Advisory until 4 PM EST this afternoon for MDZ008-012-015-
MARINE...Gale Warning until 5 AM EST Monday for ANZ430-431-450>455.
     Low Water Advisory until 7 PM EST this evening for ANZ430.



Near Term...CMS/Robertson
Short Term...CMS
Long Term...Klein
Tides/Coastal Flooding...Klein is the U.S. government's official web portal to all federal, state and local government web resources and services.