Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 220015
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
715 PM EST Tue Nov 21 2017

.SYNOPSIS...
Pennsylvania will remain under a mean upper level trough through
the week, with a succession of shortwaves and accompanying cold
fronts pushing southeast across the state.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Warm daytime temperatures from the return flow and strong 850MB
winds forming a low level jet will keep gusty winds across the
region through the afternoon and early evening. The latest
models have continued the warming trend with 12Z model
soundings become well mixed through at least 850mb, so have
increased daytime maxes by a few degrees accordingly. The latest
CAMS show the mixing should continue until around 22 to 23Z.
 Latest satellite has bands of cirrus over the region. Mid to
low level clouds will increase tonight as a cold front treks
across the central Pennsylvania. There is a lack of a moisture
with this system, however there remains impressive large scale
forcing ahead of a potent mid level shortwave that should
support a period of light rain beginning between 00Z to 03Z.
That should change to snow across the northwest mountains after
06Z tonight. The GFS, NAM and EC all showing a band of 850-700mb
fgen forcing within right jet entrance region, resulting in
bulk of precip falling in colder air behind surface cold front.
So even though latest models have around a tenth of an inch in
moisture, it should be in the regions with the best forcing and
colder air through the NW mtns. Given this, have increased QPF
and snow amounts slightly. Expecting around an inch to an inch
and a half through Warren and an inch through far western
McKean.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
As the front moves eastward through Pa early Wednesday the
bands of rain/snow should diminish as it pushes southeast. The
HREFV3 data supporting only slight chance of measurable precip
southeast of the Allegheny Plateau. However, incipient secondary
low off the Mid Atlantic coast could clip the southeast
counties with a period of rain Wednesday morning.

The brief period of lake effect snow showers Wed morning will
end by mid to late Wednesday morning as the approach of high
pressure and falling inversion heights should result in minimal
accums early in the day across the western mountains. For most
of central Pa, Wednesday should be dry and breezy with temps
below normal. GEFS mean 8h temps between -4C and -9C should
translate to highs from the low 30s across the high terrain of
northwest Pa, to the upper 40s across Lancaster Co.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
High confidence a period of fair and seasonable weather for
Wednesday night through Friday, thanks to high pressure
tracking from the GLAKS to the mid Atlantic region. Moderating
temps for Friday into Sat as return SW flow arrives ahead of a
fast moving cold front tracking from the northern Plains to the
ern GLAKS by Sat morning. A light mix of RW/SW is possible along
the PA/NY border with the front, followed by post frontal lake
effect regime Sat PM through Sunday. Fair weather arrives for
all Sun night through Tuesday with strong high pressure
rebuilding across the region.

There remains to be fairly good agreement in the large scale
features this weekend through early next week. Initially below
normal temperatures early next week will moderate as return SW
flow reaches the region Tuesday ahead of another approaching
cold front for Tue night-Wed.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Weak band of showers pushing into NW Ohio early this evening,
but airmass over central PA on the dry side.

Thus other than the BFD and JST TAF sites, hard to see nay
rain and snow showers with reduced cigs later tonight and
early Wed.

Gusty downslope winds at IPT for several more hours.

Left some fog in at MDT and LNS late tonight, based
on earlier TAF packages and latest guidance. Not sure this
will happen, given the low dewpoints, but left in for now,
may take out later.

Overall pattern favors no big weather systems into the
upcoming weekend, but frontal passages with limited moisture
every few days.

Outlook...

Thu-Fri...No sig wx expected.

Sat...Chance of rain/snow showers.

Sun...Chance of snow showers across the NW in the morning.
Otherwise no sig wx expected.

&&

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

&&

$$
SYNOPSIS...Fitzgerald
NEAR TERM...Fitzgerald/Ceru
SHORT TERM...Fitzgerald/Ceru
LONG TERM...DeVoir
AVIATION...Martin



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