Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 202224
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
524 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/...
The last of the scattered showers associated with low level jet
over the eastern Grt Lks are lifting north of the border, so
will remove mention of rain for the rest of the evening. Will
reintroduce a slight chance of showers toward dawn over Warren
County associated with approaching cold front.

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. Dewpoint
depressions already quite low at 22Z in some spots, so expect
patchy fog to form this evening and become more widespread late
tonight. Mins will range from the middle to upper 50s across
the west, and lower to middle 50s central and even some upper
40s likely over portions of the Susq River Valley.

&&

.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 portions of Central and Western PA. 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. by evening. This will hold down
highs over the northwest, but allow another day of 60s and 70s
elsewhere.

Showers will accompany the front later Wed morning (NW) and
during the afternoon and evening elsewhere across the Central
Mountains, then Lower Susq Valley. Considered thunder
possibility but instability appears absent this go around.
Colder air to come Wednesday night thanks to strong 1040 mb high
pressure buildings eastward from the Midwest.

&&

.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 /22Z TUESDAY THROUGH SUNDAY/...
Most areas improved to VFR for this afternoon, except for KIPT
which keeps some MFVR cigs into mid afternoon.Patchy fog / low
ceilings edge back into the Susq Valley from the east tonight
into Wed morning, then give way to VFR conditions across most of
the region. 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 likely in rain showers mainly NW half.

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

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

&&

.HYDROLOGY...
Recent rainfall and snowmelt has resulted in very saturated 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 some sites at or above record highs for today.

CLI data will be out by 530 - 6 PM. See CLI data for more
details later this aft.

Record highs for selected sites for Tuesday and Wednesday
February 20th and 21st:

MDT: 72/1930;71/1997
IPT: 67/2016;69/1930
BFD: 58/2016;64/1997
AOO: 62/2016;71/1997

&&

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

&&

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



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