Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 140329
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1029 PM EST Thu Dec 13 2018

.SYNOPSIS...
Weak low pressure will exit the Commonwealth this evening as
a ridge of high pressure overspreads the state tonight. A slow
moving storm system over the Gulf Coast states will track
northeast to the Mid Atlantic region this weekend, bringing
periods of rain Friday afternoon through Sunday. Cooler and
drier conditions are expected Monday and Tuesday with lake
effect snow showers and flurries over the west and north.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
SW flow aloft with heights increasing tonight ahead of next
weather system. At the surface decent radiational cooling early
this evening. Expect temperatures to level out or even rise a
bit with mid and high clouds approaching.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
Focus on Friday will be on the arrival of rain associated with
slow moving cut off low lifting out of the Mississippi River
Valley. Deep southerly flow and rich deep layer moisture will
overrun cool/stable air residing over PA, causing rain to
overspread the southern half of the state during the afternoon.
12z models in good agreement on timing for Friday PM and night.
Periods of rain to continue for much of the weekend, especially
over the southern 3/4 of the state.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
A southern stream closed low is still expected to impact Central
PA this weekend, as it migrates from the Lower MS Valley into
the Mid-Atlantic region. An initial shot of precipitation is
anticipated Friday night into Saturday morning, followed perhaps
by a brief lull, then more steadier precipitation Saturday
night into Sunday. Due to a distinct lack of cold air, a
primarily rain event is foreseen. The one potential exception to
this is late Saturday night into early Sunday over the Northern
Mountains, when a small window for freezing rain exists, if
surface based temperatures can lower enough.

By Sunday night, a colder and drier northwest flow regime will
settle in, as surface low pressure deepens off the New England
coast, and high pressure slowly approaches from the Midwest.
Typical lake enhanced snow showers/flurries are foreseen over
our Northwestern Mountains and the Laurel Highlands through
early Tuesday. However, the lack of both deep moisture or a very
strong cold push should produce light amounts. South and east
of the higher ridges, over much of Central PA, the weather
looks dry.

Wednesday and Thursday, as the flow aloft flattens out, and
surface high pressure moves towards the east coast, generally
dry weather should continue, with gradually modifying
temperatures.

&&

.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
Adjusted the 03Z TAF set some. Some low clds at times, but
mainly clear across most of the area.

Strong inversion resulting in radiational cooling and expect
more in the way of fog and hz overnight.

Earlier discussion below.

For the 00Z TAF set, minor changes to the 21Z TAF
input.

Made some changes to the TAFS on the 21Z updates.

First change was to adjust for clearing taking place now.

Second change was to add haze and fog to some sites, given
lack of wind and a strong inversion.

Third change was to add a group just before 18Z Friday to
improve conditions ahead of the rain, which looks like it
will be on the light side to start and not much before
sunset.

Rain will spread from south to north Friday afternoon and night
and continue on and off throughout the weekend, with restrictions
expected through Sunday.

.Outlook...

Sat-Sun...Ocnl rain and MVFR cigs.

Mon-Tue...MVFR cigs/snow showers psbl north/west airspace.

&&

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

&&

$$
SYNOPSIS...Ross/DeVoir
NEAR TERM...DeVoir/Fitzgerald
SHORT TERM...DeVoir/Fitzgerald
LONG TERM...La Corte
AVIATION...Martin


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