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000
FXUS61 KPHI 220852
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
352 AM EST Wed Jan 22 2020

.SYNOPSIS...
High pressure will build eastward across the Mid Atlantic and
northeast states today through Thursday. This high will weaken
and retreat to the northeast Friday before a storm system moves
across the Mid Atlantic and northeast states late in the week
and into the weekend. This low will strengthen as it moves into
the Canadian Maritimes early next week while high pressure
builds to our southwest, then across the east coast by the
middle of the week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Expansive high pressure over the Ohio and Tennessee Valleys
will build east throughout the day, and should be nearly
overhead by late afternoon.

Clear and cold this morning with temperatures generally in the
teens, but winds will be light, so not much in the way of a wind
chill.

Abundant sunshine on tap today, and with WAA and increasing low
level moisture, highs will top off in the 30s to around 40.
These temperatures will be right around normal for this time of
year.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
High pressure will be over the area tonight. With the center of
the high right over New Jersey, winds will be calm and skies
will be clear. This will allow for excellent radiational cooling
conditions. With a slightly warmer airmass over the region,
lows will generally drop into the teens and low 20s, which will
be a few degrees warmer than this morning.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Quiet weather continues through the beginning of the long term
forecast, then unsettled weather returns for the end of the week
into the weekend, then quiet weather is expected to return
again early next week.

High pressure remains across the Mid Atlantic and northeast
states through Thursday, keeping dry, quiet weather in the
forecast. Temperatures warm above normal by Thursday as
thicknesses increase. Actually, temperatures through the
extended period are forecast to be above normal.

The high pressure will begin to weaken and retreat to the
northeast by Thursday night and Friday. The forecast remains dry
through Friday, however, cloud cover will be on the increase in
advance of an approaching storm system as a couple of short
wave moves across the area.

The main story of the long term forecast continues to be the
storm system over the weekend. An area of low pressure will be
lifting across the Mid-West and into the Great Lakes Friday into
Friday night, while lifting a frontal system toward the Mid-
Atlantic region. A secondary low is forecast to develop to our
southwest across the central Appalachians Friday night near the
triple point of the occluding frontal system, then lift to the
northeast near our region Saturday, and strengthen and become
the main low of the storm system. There continues to be slight
timing and placement differences with the development of this
secondary low, and this will have an impact on the precipitation
type. The GFS continues to be faster and closer to the coast,
while the ECMWF is slower and farther inland, although the
differences are not as big as last night. What this leads to is
the potential for a wintry mix for areas along and north of I-78
starting Friday night and continuing through Saturday into
Saturday night. Areas along the I-78 corridor may change over to
all rain for a time Saturday, before changing back to snow by
Saturday night. Areas farther north, especially along and north
of the I-80 corridor will likely remain all snow during the
event. Those areas that see all snow may end up with several
inches of snow, while areas farther south could see a couple of
inches along with some icing. Areas farther south of the I-78
corridor will likely remain all rain until Saturday night into
Sunday as the precipitation changes to snow for many areas as
colder air wraps around the low as it moves to the northeast.
Any precipitation will begin to end later Sunday into Sunday
night as the low pulls farther away from the area.

High pressure will build to our southwest early next week,
while low pressure moves through the Canadian Maritimes. Winds
will become gusty due to a tight pressure gradient between the
low to our northeast and the high to our southwest, beginning
later Saturday, and continuing through Monday. Dry weather will
return to the forecast for Monday and continue into Tuesday. As
high pressure begins to build toward the east coast Tuesday,
winds will begin to diminish as well.

&&

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

Today...VFR/SKC. LGT/VRB winds this morning, becoming SW 5-7 kt
this afternoon. High confidence.

Tonight...VFR/SKC. LGT/VRB winds. High confidence.

Outlook...

Thursday-Friday...VFR conditions will continue through the
period. Winds will be fairly light through the period. -High
confidence.

Friday night...Conditions begin to lower to MVFR the IFR
overnight as precipitation moves into the area. Rain is expected
across southeast Pennsylvania, central/southern New Jersey,
Delaware, and eastern Maryland. A wintry mix is possible across
portions of northeast Pennsylvania and northern New Jersey.
Light winds become easterly overnight -Moderate confidence.

Saturday-Saturday night...Precipitation continues across the
area with IFR conditions in place. Winds shift front easterly,
to north, to northwest and become gusty 15-25 knots at times.
-Moderate confidence.

Sunday...Conditions improve to MVFR then VFR during the day.
Wind remain northwest 20-30 knots. -Moderate confidence.

&&

.MARINE...
Sub-SCA conditions with high pressure building into the region.
Light north winds today, then light and variable winds tonight.
Seas 1-3 feet on the ocean and 1-2 feet on DE Bay.

OUTLOOK...

Wednesday-Thursday...Conditions expected to remain below
advisory levels.

Thursday night-Friday night...Winds expected to remain below
advisory levels, however, seas are expected to build above
advisory levels to 5-7 feet.

Saturday-Sunday...Seas remain above advisory levels, and winds
are expected to increase above advisory levels as well. There
may be a brief period of gale force winds during the day
Saturday.

&&

.TIDES/COASTAL FLOODING...
The combination of a new moon on Friday, along with an onshore
flow may lead to areas of coastal flooding with the high tide
Saturday.

&&

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

&&

$$
Synopsis...Robertson
Near Term...MPS
Short Term...MPS
Long Term...MPS/Robertson
Aviation...MPS/Robertson
Marine...MPS/Robertson
Tides/Coastal Flooding...Robertson