Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 220034

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

A very dry period is in store after a weak, dry cold front
passes through overnight and early in the morning. High pressure
will then hold until another cold front with meager
precipitation rolls through in the middle of the Holiday
weekend. After that, high pressure will build back in for
several more days.


Sky has cleared for the moment, but the front and associated
clouds are on the way in from the NW. The wave rolling along the
east coast is also moving steadily this way. The timing of
precip onset is right around midnight in Warren County, but it
will take another 6 hours to get near to the Allegheny Front. By
the time it gets there, the moisture will be drying up almost
completely. The precip should only take an hour or so to turn
from the initial rain to snow. Initially warm ground may make
for icy patches on the roads as the melted snow freezes up
later in the night. Going accums looks fine at just 1.5" or less
in the far NW. Temps have dropped off very quickly at THV and
MDT where it is in the 30s. CXY hanging in at 48F, but MDT only
39F. Gotta love micro climate. Expect anything that falls from
the sky in the SE overnight to be trying to work down from far
aloft and also to be liquid with dewpoints in the 30s. Keeping
the POPs less than 30pct there, but decent frontogenesis aloft
around 8H could make a stripe of very light rain for a few


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.


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.


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.


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.




NEAR TERM...Dangelo
SHORT TERM...Dangelo/Fitzgerald/Ceru
AVIATION...Martin is the U.S. government's official web portal to all federal, state and local government web resources and services.