Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 210323
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1023 PM EST Tue Feb 20 2018

.SYNOPSIS...
An anomalous upper level ridge will remain parked off the
southeast coast through the upcoming week. At the surface, a dying
cold front will push southeast across the area late Wednesday,
then stall in the vicinity of Pennsylvania late this week into
the weekend.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
A very mild February night is in store for the area within
broad southwest flow circulating around Bermuda high. Mostly
clear skies and light wind will likely result in areas of fog
tonight over the eastern portion of the forecast area, where low
level cool air wasn`t completely scoured out today. KIPT already
down to 1/4sm at 03Z and dewpoint depressions are quite low
across most of the Susq Valley, so expect patchy fog to become
more widespread late tonight. Mins will range from the mid to
upper 50s across the high ground of the Alleghenies to the mid
40s in parts of the Middle Susq Valley.

Will introduce a slight chance of showers toward dawn across
Warren County associated with approaching cold front.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
The warmth continues into Wednesday, with a spring like start
to the day. Areas of fog especially east will give way to mixed
clouds and sun with near-record to record high temps across
much of the forecast area. A weakening area of showers will
accompany a cold front dropping across the commonwealth
Wednesday, beginning mid to late morning NW and reaching into
the Lower Susq Valley by evening. This will hold down highs
over the northwest, but allow another day of 60s and 70s
elsewhere.

Colder/drier air to come Wednesday evening thanks to strong
1040 mb high pressure buildings eastward from the Midwest.
Stalled frontal boundary south of Pa will begin to return
northward late Wed night, spreading rain into much of the
region, with mixed precip likely along the northern tier.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Did not change a lot for the period Wednesday night into Friday.
Current fcst looks good. Potential for a significant change in
practical weather...if frontal position changes very much. Some
downward adjustments made earlier today on ice amts. My main
change was to add additional grids.

Still looking like another warm up on Sunday. Potential
for some heavy showers across the west...but several days
out.

Still looks dry behind the front Sunday Night...so I took
out the showers of the fcst after 06Z Monday.

Left Monday into Tuesday dry...weak system fcst to cut under
the ridge...but not seeing much moisture with this.

More information below from earlier shifts.

*Periods of rain with a several hour period of icing from
 freezing rain expected late Wed night through Thur morning.
 brief interval of mixed precip possible Wed. night- AM Fri. A
 light accumulation of snow could precede the freezing rain
 across the Northern Mountains early Thursday.

*Pattern favors above average temperatures this weekend into
 next week

The cold front will become quasi stationary near the MD line
Wed. night. The wavy frontal boundary will bring periods of rain
into the weekend, with several (to as much as 8) hour period of
mixed wintry precip likely across mainly the Central and
northern mountains Wed. night and Thu morning, thanks to an
increasing and moderately strong northerly, 1000 mb
Ageostrophic flow that will serve to pump shallow/sub-freezing
air south into the region.

Confidence is moderate with respect to the exact ptype details
(and the location and amount of fzra). However, there is at
least some risk for a light snow and/or ice accumulation. We`re
in good agreement with WPC`s Winter Weather graphics ATTM, with
a coating to 2 inches of snow possible at the onset across parts
of northcentral and NW PA, before a changeover to sleet and or
Freezing Rain.

Another round or two or rain is likely over the weekend. We
will need to monitor the potential for flooding especially
across south- central PA where the ground is very saturated from
previous rain/snowmelt and streamflows are well above normal.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Patchy fog to form again overnight at most airfields under
clear skies and generally calm to light southwesterly winds.
Over the eastern airspace expect thicker fog/ low ceilings
to redevelop / move back into the Susq Valley from the east
into Wed morning where a tongue of higher surface dewpoints
exists.

VFR conditions should return to the region later Wed morning.
An exception will be over the NW mtns as a sharp cold front
will spread rain and restrictions in from the NW, with
restrictions possible in the afternoon/evening into the central
mountains.

That will be followed by several weak waves of low pressure
bringing bouts of rain for the second half of the week, and even
some light freezing precipitation Thursday morning.

Outlook...

Wed...Restrictions from fog early then likely in rain showers
mainly NW half.

Thu...Widespread restrictions in rain south/wintry mix north.

Fri-Sun...Widespread restrictions in periods of rain.

&&

.HYDROLOGY...
Recent rainfall and snowmelt has resulted in wet soil and well
above normal streamflows across much of the area especially
south-central PA. Rainfall of 0.50 to 1.00 inch is forecast
between Wednesday and Thursday night, with additional rainfall
likely into/over the weekend. River flood potential (including
small streams, creeks and tributaries) is above normal and we
will continue to monitor the risk in the coming days.

&&

.CLIMATE...
Looks like another day of record highs across southern Pa
Wednesday. Here are current records for Wednesday February
21st:

MDT: 71/1997
IPT: 69/1930
BFD: 64/1997
AOO: 71/1997

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...Fitzgerald
NEAR TERM...Fitzgerald
SHORT TERM...DeVoir/Fitzgerald
LONG TERM...Lambert/Martin
AVIATION...DeVoir
HYDROLOGY...
CLIMATE...



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