Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 140816
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
316 AM EST Fri Dec 14 2018

.SYNOPSIS...
High pressure over the Gulf of Maine continues to drift out to
sea today. Low pressure over the lower Mississippi Valley will
track to the north and east today, then a new low pressure
system forms over the Mid-Atlantic tonight before moving out to
sea on Saturday. Low pressure then continues to work its way
through the region on Sunday. A cold front moves across the
region on Monday, followed by high pressure for much of the new
week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Low level moisture has increased overnight and quite a bit of
fog and low clouds have developed across the forecast area.
Additionally, areas of patchy drizzle will develop as there is
sufficient lift present in the moist layer and will then persist
through around mid day. In the colder areas of the Poconos and
northern New Jersey, some patchy freezing drizzle may occur
through this morning before temperatures rise above freezing.

High pressure centered off the coast of New England will nose
westward across our area for today. Unfortunately, this will
keep us in the easterly, onshore flow and we are not likely to
see much improvement in conditions for the day. Cloudy skies
will remain through the day but with a more southerly component
to the surface flow, we will benefit from some warmer air
pushing northward into the region. As a result, high
temperatures will be on average around 5 degrees above normal.
Highs will range from the low to mid 40s across the Poconos and
northwest New Jersey to around 50 through the I-95 corridor to
mid 50s across Delmarva.

A low pressure system will be located to the southwest of our
area today. As this system starts to push northward, we will see
increasing chances for rain, from south to north this
afternoon. Guidance continues to slow the onset of precipitation
across the area so while we may some showers arrive by this
afternoon, the bulk of the rain is not expected to move into the
forecast area until this evening.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Broad low pressure over the Gulf Coast states, fairly
vertically stacked low pressure from the surface up to 300 mb,
continues to track to the east tonight. A new area of surface
low pressure develops out ahead of it over the Mid-Atlantic
states as 100-110 kt jet streak moves into the Mid-Atlantic out
ahead of the primary system this evening, and this new low will
pass south of Delmarva late tonight, and then out to sea on
Saturday.

00Z model trends keep the heaviest rain in far southeast PA,
southeast NJ, and Delmarva, generally along and south of I-195.
PWATs will generally range from 1-1.25" from the southern
Poconos to around I-195, and then from 1.25-1.5" from there down
to Delmarva. 3 hour and 6 hour FFG values are fairly high,
generally 3-4", and 1 hour FFG guidance values are around 1 inch
in northern zones, and 2-3" in southern zones where the
heaviest rain should fall. Although some minor poor drainage
flooding is possible, do not expect widespread flooding, so will
not issue a Flood Watch at this time.

During this time, storm total QPF values should be around 1/2"
to 1" for the northern half of the forecast area, and from
1-1.5" in the southern half with the heaviest rain falling late
this evening through Saturday morning. Minimal additional QPF
possible through Saturday afternoon as some shortwave energy
tracking east develops another weak surface low over the Mid-
Atlantic.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
The primary low moves towards the Mid-Atlantic Saturday night,
and then passes across Delmarva Sunday morning before moving out
to sea during the day. This system has some fairly cold air
associated with it, especially across northern zones.
Temperatures Saturday night will drop into the low to mid 30s
for far northern zones, generally along and north of I-80, and
from the upper 30s to low 40s from I-80 down through southern NJ
and SE PA. Lows will be a bit warmer in Delmarva. As a result,
do think this will allow for a period of snow, or at least a
rain/snow mix, for the northern areas Saturday night. Important
to note that NAM BUFKIT profile soundings indicating a freezing
rain profile in Mount Pocono Saturday night and Sunday, while
GFS BUFKIT profile is much warmer at Mount Pocono, keeping
precip all rain. For now, will keep precip as snow or rain/snow
and will shy towards the NAM and not the GFS for Sunday. Low
pressure moves out to sea on Sunday, and then the upper low
cross the region Sunday night. More cold air seeps into the
region allowing for the snow line to creep southward through the
Lehigh Valley and northern NJ, and more in the way of a
rain/snow mix spreads into all but southern Delmarva.

A cold front moves across the region on Monday, and a surge of
arctic air infiltrates the region Monday night and Tuesday. Some
snow showers possible across southern Poconos and northern NJ
with passage of cold front and with some lingering Lake Effect
snow bands.

High pressure then builds into the region for the middle of
next week with dry conditions through Wednesday. Another storm
system will dig through the nation on Thursday, and some precip
may develop out ahead of it by Thursday afternoon.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Today...Mainly MVFR/IFR conditions prevail at the terminals
this morning as low clouds and fog have moved across the region,
except KACY where VFR conditions continue early this morning.
Patchy drizzle and fog will continue through mid morning before
conditions may start to improve by around midday, with an
expectation of a return to VFR for this afternoon.

Rain will develop late this morning to our southwest and begin
to move into the terminals later this afternoon.

Light winds this morning will become east to southeast mainly
less than 10 knots.

Tonight...Rain will continue to move into the area and
conditions will deteriorate through this evening and tonight.
VFR will drop to MVFR and then dropping to IFR late tonight.
Winds become light and variable through tonight.

Outlook...

Saturday through Saturday night...Periods of MVFR or lower in
rain. NE winds 10 kt or less, increasing to 10-20 kt Saturday
night.

Sunday...Periods of MVFR or lower in rain, except rain/snow
possible at KRDG/KABE. NE winds 10-15 kt.

Sunday night...MVFR in rain/snow possible. N winds becoming NW
10 kt or less.

Monday...Generally VFR conditions. Brief snow showers possible
at KABE. NW winds 10-20 kt, with gusts to 25 kt.

Monday night through Tuesday...VFR. NW winds 10-20 kt with
gusts up to 25 kt.

&&

.MARINE...
Sub-Small Craft Advisory conditions are expected to continue on
the area waters through today. East to southeast winds around
10 to 15 knots with a few gusts around 20 to 23 knots, mainly on
the northern waters this morning. Seas will be around 2 to 4
feet on the ocean and around 1 to 3 feet in the Delaware Bay.

Tonight...Generally sub-SCA conditions. VSBY restrictions in
rain/fog.

Outlook...

Saturday and Sunday...SCA conditions with NE winds increasing
to 15-20 kt with 25-30 kt gusts. Gale force gusts possible on
northern NJ ocean waters Saturday night and Sunday. Ocean seas
building to 6-10 feet.

Sunday night through Monday...SCA conditions remain on the
waters. Winds will remain gusty out of the north to northwest
around 15 to 20 knots with gale force gusts possible.

Tuesday...Winds and seas should be gradually diminishing but
could remain above SCA criteria for much of the day.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$
Synopsis...MPS
Near Term...Meola
Short Term...MPS
Long Term...MPS
Aviation...Meola/MPS
Marine...Meola/MPS


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