Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 201422
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
922 AM EST Mon Nov 20 2017

.SYNOPSIS...
High pressure over the southern Mississippi River Valley will build
east, then move off the Mid-Atlantic coast tonight. A cold front
will approach Tuesday night and pass through the area on Wednesday.
At the same time, low pressure over the southeast portion of the
country will approach the Mid- Atlantic and move out to sea. High
pressure will build through the area by the end of the work week. A
cold front is expected to pass through on Saturday, with high
pressure gradually building east early next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Flurries are gradually diminishing across the higher terrain and
this trend will continue through late morning. As the diurnal
boundary layer becomes better established, GOES 16 preliminary
non-operational satellite imagery is already indicating the
expansion of low cloudiness across the higher terrain. NAM Nest
Model soundings are also showing this trend, so increased sky
cover across the higher terrain of northern NJ and eastern PA
today. Temperatures will be several degrees below normal today
with westerly wind gusts of 25 to 30 mph.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
The surface high will progress offshore to our south tonight, and
midlevel flow will become more southwesterly as a vort max digs
southeastward into the Upper Midwest by 12Z Tuesday. Low-level warm-
air advection should be in full swing by the overnight hours, and
this will prevent much of a fall in temperatures, despite the
lighter winds and mostly clear skies expected.

Once again, statistical guidance is in good agreement regarding
temperatures, so a blend was used for lows. Generally expecting
readings around average. Temperatures may actually flatline
relatively early in the night as warm-air advection increases via
increasingly more favorable low-level trajectories.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
High pressure over the Mid-Atlantic is expected to move off the Mid-
Atlantic coast on Tuesday. Return flow sets up, and highs on Tuesday
will be about 3-5 degrees above normal, topping off in the 40s in
the Poconos, otherwise in the low to mid 50s north and west of I-95,
and near 60s in the Delmarva and southern NJ. S to SW winds increase
Tuesday afternoon to 15-20 mph with gusts up to 30 mph.

Low pressure is expected to develop over the Gulf Coast on Tuesday,
move off the Southeast U.S. coast Tuesday night, then approach the
mid-Atlantic coast before moving out to sea on Wednesday. A cold
front will pass through the region Wednesday afternoon. Based on
latest model guidance, will continue a swath of likely PoPs across
southern DE and southeast NJ, and chance PoPs for most areas south
and east of the Fall Line. Cooler temps will move into the Poconos
Wednesday afternoon, but stronger CAA will not get underway until
Wednesday night.

Chilly high pressure builds through the region Thanksgiving Day
with temperatures 6-8 degrees below normal. Highs top off in
the mid and upper 30s in the Poconos, otherwise in the low to
mid 40s.

High pressure reestablishes itself over the area Friday with
highs a few degrees warmer than Thursday.

Low pressure passing well north of the region will drag a cold
front through the region on Saturday, and then low pressure remains
over eastern Canada through next weekend even as surface high
pressure begins building in from the west. Unsettled weather
possible.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Today...VFR with west winds increasing to 10 to 15 kts with gusts to
25 kts. Confidence above average.

Tonight...VFR with west winds decreasing quickly after sunset and
likely becoming southwesterly with time. Speeds generally below 10
kts. Confidence above average.

Outlook...

Tuesday...VFR. SW winds 15-20 KT with gusts up to 25 KT Tuesday
afternoon.

Tuesday night and Wednesday...Mainly VFR. Rain possible south
and east of I-95 Tuesday night through Wednesday morning with
MVFR or lower conditions. SW winds 5-10 KT become NW Wednesday
afternoon and increase to 10-20 KT.

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

Friday...VFR. NW winds 5-10 KT.

Saturday...VFR early...then MVFR or lower conditions possible in
rain showers later in the day. SW winds 10-15 KT.

&&

.MARINE...
900 am update: Observing platforms, including Brandywine Shoal
Light in the lower Delaware Bay, indicated wind gusts below
gale force as of around 715 am with a continued downward trend
at this time. Model guidance, including the HRRR and RAP, are
in agreement with this trend as well.

Trend with the winds will be downward today, but small craft
advisory conditions will continue through the morning for
Delaware Bay and the Delaware coastal waters and through much of
the day off the New Jersey coast.

There will likely be a brief lull in winds off the New Jersey coast
late this afternoon and this evening before southwest winds pick up
again overnight. For this reason, kept the small craft advisory
going through Monday night.

Outlook...

Tuesday and Tuesday night...Brief lull in SCA conditions through
Tuesday morning. Otherwise, 25-30 KT wind gusts, primarily on the
ocean waters, may possibly over Lower DE Bay Tuesday afternoon.

Wednesday...Lull in SCA conditions possible Wednesday morning.
Otherwise, winds shift to the NW and increase to 15-20 KT with
25-30 KT gusts.

Thursday through Saturday...Sub-SCA conditions expected.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 6 AM EST Tuesday for ANZ450>453.
     Small Craft Advisory until 1 PM EST this afternoon for ANZ430-
     431-454-455.

&&

$$
Synopsis...Miketta
Near Term...CMS/Franck
Short Term...CMS
Long Term...Miketta
Aviation...CMS/Miketta
Marine...CMS/Franck/Miketta



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