Area Forecast Discussion
Issued by NWS State College, PA

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839
FXUS61 KCTP 261821
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
221 PM EDT Mon Sep 26 2016

.SYNOPSIS...
A cold front with a line of showers will sweep through the region
overnight. A developing deep cut-off low will bring cool cloudy
weather into the region late Wednesday and into early this
weekend. The deep cold air should trigger showers Thursday through
most of the coming weekend before it slowly begins to lift out.

&&

.NEAR TERM /THROUGH TONIGHT/...
Forecast has not changed much in the HRRR and NCEP models. The
front is a bit slower and there is a lead band of showers/isolated
thunder in western PA now.

The cold air damming in central areas has held on well and the
cool stable air remains to the east.

Showers will move into western areas over the next few areas with
main area to the west still just entering PA. The unforecast lead
band in southwest PA could bring a shower to Clearfield-Cambria
and Somerset in the next 1-3 hours well ahead of the larger scale
band of rain.

HRRR pretty much, the the GEFS, has a 3 hour window for most areas
of rain and exists all the rain 0.10 or more rainfall to our east
in the 06 to 09Z rain. Some lingering light stuff in extreme east
probably a bit later than 09Z.

Dry air behind front should clear it out. Do not expect lingering
low clouds and fog behind this front.

&&

.SHORT TERM /TUESDAY/...
Sunny breezy day some clouds especially in mountains. Probably the
best day of the week. No real anticyclone behind front due to
building trough to our west and wave along the coast.

But -1sigma PW and 6-10C 850 mb temperatures imply a pleasant
early autumn day. It could be breezy a few hours after sunrise and
the winds should diminish in the late afternoon.

My bet is the statewide is the best day of the week as the cut-off
is going to make things ugly by Wed-Thu.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Big change in the weather pattern will set up with a long wave
trough and a cut off low dropping down over the Eastern U.S. and
several days with rain in the forecast.

Tuesday night into Wednesday morning will see some drying and
seasonable temperatures behind the cold front. But a large upper
level low is dropping southeast across the Great Lake Region. By
Wed afternoon the upper low is over Ohio and moisture is being
pulled back north along the Eastern Coast into PA. Chances for
rain showers will increase Wed afternoon with periods of rain
showers likely Wed night into Thurs night as the low continues
south into Western VA. Friday the low begins to shift back to the
northwest continuing the wet pattern into Saturday. Models hint
that Central PA may be dry slotted for a bit friday afternoon and
night. Upper low begins to lift northeast Saturday into Monday
with gradually decreasing POPs. Lower Susq will be driest over the
weekend and dry Monday with increasing chances farther north
across the higher terrain of the northern tier where chances will
linger into Monday morning. Temperatures will be a little milder
at night but cooler during the day with clouds and periods of
showers thereby averaging around normal.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Updated the TAFS with the latest guidance and tweaked shower
timing to the 16Z HRRR. VFR will dominate the rest of today. Some areas
of MVFR in west as the front is entering westernmost PA this
afternoon. There are considerable areas strong surface winds which
could affect approaches.

This front will bring a 1-3 hour shot at showers and isolated
thunderstorms in the northwestern areas and mainly a 1-3 hour
shot at showers in the central and east later this evening and
early tonight. Tried to time this frontal passage over the next
12-15 hours. Expect 1 to 6 hours of MVFR and areas IFR with this
line.

Very dry air behind the front with only brief period of IFR/MVFR
as the system moves to the east. Then conditions rapidly improve.

VFR Tuesday though a breezy day.

Wed should be the last good VFR day then more showery and cloudy
conditions later in the week into the weekend suggest mix MVFR/VFR
and locally VFR.

Outlook...

Tue...No sig wx expected.

Wed...Showers/cig reductions possible late.

Thu-Fri...Sct showers/cig reductions possible, esp w mountains.

&&

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

&&

$$
SYNOPSIS...Grumm
NEAR TERM...Grumm
SHORT TERM...Grumm
LONG TERM...Watson
AVIATION...Grumm



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