Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 190708
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
308 AM EDT Tue Oct 19 2021

.SYNOPSIS...
A ridge of high pressure extending from the Upper Great Lakes to
the Lower Ohio Valley will slide east through midweek.

A cold front will pass through the state by Friday morning, and
cause showers and a few thunderstorms Thursday and Thursday
night.

Temperatures will be cool this morning before a moderating
trend starts today. Temperatures will cool back to near normal
by late week behind the cold front.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Stratocumulus cloud deck has exited off to the east as surface
ridging builds in across the Ohio Valley into the Great Lakes.

While surface dewpoints remain in the mid to upper 30s, winds
remaining in the 3-5 mph range have allowed for just enough
mixing to keep radiational cooling from being more robust this
morning. Additionally already seeing some warm air advection as
winds back westerly. Certainly will still see some valley
locales in the northern tier drop into the upper 30s, keeping
patchy frost in the offing. The least likely location for frost
will be in the south central counties.

The frost should only be patchy with min temps just getting
into the mid to upper 30s in the coldest of the eastern
valleys. Thus, we do not anticipate the need for a frost
advisory anywhere in the forecast area.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...
Patchy stratocu clouds over the nrn mtns and any river valley
fog in the morning should dissipate quickly between 13-14Z. The
wind backs more westerly and taps milder air to our west through
the day. So, even without a notable southerly component to the
wind, WAA is expected to remain in place. Deeper mixing without
the subsidence inversion overhead and nearly full sunshine
should add 5-10F onto our maxes vs. Monday`s high temps.

WAA aloft will bring a band of cirrus overhead Tues night. Low
temperatures should only dip into the mid-upper 40s early Wed,
which will be about 5-10F above normal for late Oct.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
A ridge of high pressure will slide east across the state
Wed/Wed night, providing central PA with a dry and warm
Wednesday, although it will still be breezy with gusts to 20 mph
possible. On Thursday, a sfc cold front will approach the area,
providing our next chance of showers. Thursday should still be
a warm day, as southwesterly flow advects warm air ahead of the
front.

A several hour period of moderate rain showers is expected
Thursday afternoon and evening (especially across the NW third
to half of the CWA) as a potent low-mid level southwesterly jet
of 45-55 KTS creates some pulses of mdtly strong meso-b forcing.

This forcing will spread across an area of MDT instability and
sfc based CAPE of 400-800 J/KG (locally up to 1000 J/KG near and
to the west of RT 219 in NW PA) creating the potential for
isolated/embedded TSRA that could produce some localized,
strong/gusty wet microbursts

A return to cooler temperatures is expected Friday into this
weekend as a trough sets up over the East, although it doesn`t
look like it will get quite as cool immediately behind the front
as it had on past model runs. A shortwave rounding the base of
the trough late Fri night and early Sat could touch off some
rain showers, although the timing of this shortwave is still
uncertain. Lake effect rain showers are likely to continue into
later Saturday. The ECMWF and GFS also differ on the timing of
another potential light rain maker late Sun into Mon, when some
southern stream energy may phase up with the northern stream
and a front hung up across the PA-MD border.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
Skies will clear tonight as high pressure builds into the area.
Winds will diminish at the surface overnight, but a 35-40 kt
wind will persist just off the surface and produce some LLWS.
Patchy low clouds and perhaps fog is possible in the valleys
across northern PA towards daybreak on Tuesday.

Expect widespread VFR conds on Tuesday, with a west-northwest
breeze that should be a bit less gusty than Monday.

Outlook...

Tue-Wed...Generally VFR.

Thu...Restrictions possible late in SHRA with cold frontal
passage.

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

&&

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

&&

$$
SYNOPSIS...Lambert/Dangelo/Guseman
NEAR TERM...Lambert/Dangelo/Guseman
SHORT TERM...Lambert/Dangelo/Guseman
LONG TERM...Evanego/Colbert
AVIATION...Evanego/Colbert


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