Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 200003
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
803 PM EDT Tue Oct 19 2021

.SYNOPSIS...
High pressure over the Carolinas will slide off the east coast
the second half of this week. Low pressure will track north of
Pennsylvania late Thursday, dragging a cold front through the
area. An upper level trough will swing over Pennsylvania
Saturday, then begin lifting out by late in the weekend.

&&

.NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/...
Central Pa remains under the influence of large high pressure
system and low-pwat air mass, centered over the Carolinas. An
upstream shortwave will spread nothing more than a bit of
cirrus over the region late tonight.

The pressure gradient between the high to our south and a cold
front pushing into the Grt Lks should keep the breeze up a bit
tonight, resulting in a slightly milder night than last, and
probably no fog. Expect min temps to range from the mid 40s in
the cooler valleys of the Alleghenies, to the low 50s over parts
of the Susq Valley.

&&

.SHORT TERM /7 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Upper level ridging is progged to build over the state behind
departing shortwave on Wednesday, providing fair and warm
conditions. Model soundings mix to 3-4kft Wednesday afternoon,
supporting wind gusts to around 15kts in most places. Mostly
sunny skies and modest warm advection should push temps a bit
above those of today, with highs ranging from the mid 60s over
the highest terrain of the Alleghenies, to the mid 70s across
the Lower Susq Valley.

A southerly low level jet and surge of warm advection will clip
northwest Pa Wed night, bringing an increase in clouds and the
outside chance of a shower. Elsewhere, fair weather is expected
under surface ridge. Calm winds and a mainly clear sky should
promote patchy late night valley fog across central and southeast
Pa, as the latest HREF and NAMNest indicate. 18Z GEFS 2m temp
plumes suggest lows will be similar to tonight`s, ranging from
the upper 40s to low 50s most places.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
On Thursday, a cold front will approach the area, providing our
next chance of showers. Thursday should still be a very mild
day, as southwesterly flow advects in warm air ahead of the
front.

Showers will accompany the front from west to east across
Pennsylvania Thursday afternoon and evening, and there should
be enough instability for isolated/embedded thunderstorms into
at least the western highlands. This activity should tend to
diminish as it progresses eastward across the area Thursday
evening.

A return to cooler temperatures is expected Friday into this
weekend as a trough sets up over the eastern United States. A
shortwave rounding the base of the trough Friday night or
Saturday could touch off some rain showers, although the exact
timing of this system remains uncertain.

Upper-level ridging will attempt to build into the Great Lakes
and eventually the northeastern United States early next week.
However, there are some differences in the long-range model`s
handling of energy that comes into the west coast Friday night
which would have ramifications on how quickly the ridging is
able to establish itself over us. Regardless, it looks like we
should see moderating temperatures heading through early next
week.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Clear sky but just a little gusty wind. The strength and
position of the high pressure ridge to our south won`t change
much tonight or Wed. The wind will likely stay up above 5KT
overnight at most locations, with the ridgetops of the Laurels
and northern mountains perhaps staying above 10KT. There is a
strong low level jet developing, but it will be coming from the
NW instead of a more- normal south or southwesterly direction.
The threat for LLWS will develop through the night as the llvl
inversion steepens, and continue into the morning before mixing
starts coincident with the mesoscale forcing sliding to our
east. Cirrus will spread across the state tonight, but exit
stage right in the early morning. VFR will continue Wed, but
clouds from the west will lower and thicken Wed PM.

Outlook...

Thu-Thu night...Restrictions possible late day and overnight in
SHRA/TSRA assocd with cold frontal passage.

Fri-Sat...Lingering MVFR cigs possible, mainly N/W.

Sun...AM valley fog, then --RA poss mainly S.

&&

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

&&

$$
SYNOPSIS...Dangelo
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald
LONG TERM...Evanego
AVIATION...Dangelo


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