Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 152312
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
612 PM EST Fri Dec 15 2017

.SYNOPSIS...
Surface low pressure, off the Delmarva, will track northeast
into the open Atlantic this evening. High pressure, centered
over the southeastern United States, will nose into the region
early on Saturday. This will be short-lived as a cold front,
coming in from the north, will move into or through the area on
Saturday night and Sunday. This front will then stall before
lifting northward as a warm front Sunday night and Monday. A
cold front will progress through the region around the middle of
next week. Another system may affect the area near the close of
next week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Our upper level jet enhanced light snow event was gradually
coming to an end early this evening. The back edge of the
accumulating snow was along the Interstate 95 corridor around
6:00 PM. It should be off the coast in the 7:00 to 8:00 PM time
frame.

Snowfall accumulations in the 1 to 3 inch range were common,
except in the Poconos and far northern New Jersey and in parts
of northeastern Maryland and central and southern Delaware where
totals were less than an inch.

Gradual clearing is anticipated for tonight as the system moves
farther off the coast.

A west wind should increase to 5 to 10 MPH. Minimum
temperatures are forecast to favor the teens in much of eastern
Pennsylvania and northern New Jersey, and the lower and middle
20s in southern New Jersey and on the upper Delmarva.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
Shortwave energy rotating around the based of the large scale
trough is forecast to move across the Great Lakes and Northeast
states on Saturday. At the surface, a weak area of low pressure
will pass to our north but a northwest flow behind this
disturbance will help steer a cold front southward into the I-80
corridor by the late afternoon.

Even with the deepest, more organized synoptic lift staying to
our north, models show a ribbon of low-level
convergence/frontogenetical lift near the front that could
support some snow shower activity across the I-80 and I-78
corridor during the mid to late afternoon. We are currently only
expecting minor accumulations. Elsewhere, expect clouds to
increase as the day progresses.

Forecast high temperatures range from the lower 30s across the
I-80 corridor to the lower 40s in Delmarva and coastal NJ.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Overview...The period starts with a deepening surface low off
Delmarva. This low will track to the northeast overnight into
the open Atlantic. Surface high pressure, centered across the
deep south, will push up into the Mid-Atlantic by daybreak
Saturday. This high won`t hang around long. A cold front, coming
in from the north, will move into or through the forecast area
Saturday night into Sunday. This front will back up as a warm
front Sunday night into Monday. Another cold front will push
through the region in the Tuesday/Wednesday timeframe. Surface
high pressure is expected on Thursday. This will elide to a warm
front later on Thursday into Friday and a cold front very late
in the period. Both of these fronts are associated with low
pressure moving across the eastern Great Lakes.

Temperatures...For reference, normals for KPHL are around 30
and in the middle 40s. Sunday will be slightly below normal.
Monday and Tuesday will be above normal with some mid-50s
possible across portions of the coastal plain. Wednesday looks
to be about normal with Thursday slightly below. Friday will
rebound once again with above normal temperatures. Once again,
portions of the coastal plain could see temperatures top out in
the middle 50s.

Precipitation...Small PoPs have been inserted late Sunday and
maintained into Sunday night. This associated with the warm
front in the vicinity. Small PoPs will continue into Monday and
through Tuesday night. Wednesday and Thursday will be PoP free
behind the mid-week cold front. Some chance PoPs will be
inserted into the grids on Friday.

Winds...Fairly benign through the period. Moist noticeable
winds will be right ahead and behind the cold front Tuesday and
Wednesday.

Impacts...While the forecast will see a roller coaster week
with temperatures and multiple chances of precipitation, none
are expected to create widespread hazardous weather at this
time.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

This evening...Improving to VFR with snow ending. Light and
variable wind.

Overnight...VFR. Clearing. West wind 4 to 8 knots.

Saturday...VFR. Mostly clear in the morning, then increasing
clouds. West to southwest wind 5 to 10 knots.

Outlook...
Saturday night...Generally VFR with light and variable winds.
Medium confidence.

Sunday...Generally VFR. Light northeast winds to start the day
and southeast to finish. Increasing clouds and a small chance of
precipitation later in the day. Medium confidence.

Sunday night and Monday...Generally VFR, though brief sub-VFR
conditions are possible with light rain or snow, especially
north of PHL. Light winds generally transitioning from southeast
to southwest during the period. Low confidence.

Monday night and Tuesday: Sub-VFR conditions possible, with
scattered showers during the period, especially on Tuesday.
Winds primarily southwest at 5 to 15 kts. Medium confidence.

Tuesday night and Wednesday...Generally VFR. Decreasing clouds
and showers on Tuesday night. No precipitation expected on
Wednesday. Winds west or northwest 10 to 20 mph. Medium
confidence.

&&

.MARINE...
N-NW winds expected increase this evening and become NWly as
low pressure intensifies while tracking to our east. Opted for a
SCA instead of a GLW for tonight and Saturday with winds
generally in the 25-30 kt range. However, a brief ramp up in
winds are expected late tonight when pressure rises behind the
offshore low are greatest. An isolated gust to near gale force
at our offshore buoys is certainly a possibility.

Outlook...
Saturday night: Residual advisory-level northwest winds in the
evening will diminish overnight. Gale force gusts during the
evening can`t be ruled out. Seas below criteria.

Sunday and Sunday night: Sub small craft advisory conditions.
No headlines anticipated. There may be some light rain in the
afternoon and overnight with potential for some visibility
restrictions.

Monday and Monday night: Sub small craft advisory conditions.
No headlines anticipated. Scattered showers, at times, could
create visibility restrictions.

Tuesday: Southwest winds increasing to near advisory levels by
afternoon with seas also building. A chance of showers and
visibility restrictions.

Tuesday night and Wednesday...Small craft advisory conditions
expected due to northwest winds behind the front and building
seas.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Winter Weather Advisory until 9 PM EST this evening for PAZ070-
     071.
     Winter Weather Advisory until 7 PM EST this evening for PAZ102-
     104-106.
NJ...Winter Weather Advisory until 9 PM EST this evening for
     NJZ012>027.
DE...Winter Weather Advisory until 9 PM EST this evening for
     DEZ001>003.
MD...Winter Weather Advisory until 9 PM EST this evening for MDZ008-
     012-015-019-020.
MARINE...Small Craft Advisory until 1 AM EST Sunday for ANZ452>455.
     Small Craft Advisory from 11 PM this evening to 1 AM EST
     Sunday for ANZ450-451.
     Small Craft Advisory from 1 AM to 6 PM EST Saturday for ANZ430-
     431.

&&

$$

Synopsis...Kruzdlo
Near Term...Iovino
Short Term...Klein
Long Term...Kruzdlo
Aviation...Iovino/Kruzdlo
Marine...Klein/Kruzdlo



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