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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

                            
000
FXUS61 KCTP 232119
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
419 PM EST Sat Feb 23 2019

.SYNOPSIS...
A complex frontal system will move into the forecast area tonight
and move through the region Sunday. Very windy conditions will 
will develop in the wake of the cold front Sunday afternoon, 
and will continue into Monday. Colder and mainly dry conditions
will prevail for much of the upcoming work week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
The first of the spotty light rain is streaking NE over the area
as of early afternoon. This spotty mainly light precip will
continue into the overnight, before becoming steadier and
heavier after midnight.

Temperatures over the higher elevations are still hanging tough
a degree or two either side of freezing, bringing about reports
of some light icing at Johnstown and Somerset airports. The 
HREF shows the ridges having this light freezing rain/drizzle 
right into the evening hours so we will keep the advisory
running through 7PM. It may need to be extended, that will have
to be monitored. Ice amounts will be light, but any ice can 
cause travel problems.

QPF through 00Z will vary from a few hundredths of an inch 
across the NE half of the CWA, to around an one tenth of an inch
in the southwest zones.

Models agree in ramping the precip up after midnight as the
occlusion enters western PA. Guidance shows a pretty solid cold
air damming scenario overnight, so while temperatures will
remain steady or even rise slowly, it will not mix out quickly
and will lead to a chilly rain.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
The occlusion/cold front will hop across the CWA during the
morning through mid afternoon. Temperatures will actually spike
up once the front mixes out the cold air damming wedge, so 
temperatures will begin rising early in the day and continue 
through about mid afternoon when the cold air begins to make a 
return once again. 

Models do erode stability somewhat, indicating the potential for
an elevated thunderstorm as the front enters the area. 

The big thing for Sunday will be the potential for strong
damaging wind gusts to develop behind the cold front. Winds
aloft will be well aligned up through at least 500mb where
progged speeds exceed 100kt by mid to late morning. I'd like to
see a better isallobaric pressure couplet entering the region, 
but the cold advection should be enough to bring about some deep
mixing and allow us to tap the strong winds aloft for some 
warning criteria wind gusts. The ridges will be the most likely 
areas to really blow hard.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Deep low pressure lifting north of the Great Lakes area late 
Sunday will likely reset the large scale pattern. 

Thus given the the above feature, the airmass to the north and 
west, and latest guidance, did lower temperatures a few degrees 
for some periods Sunday night into Friday. These changes also
fit in better with others.

Did look at taking rain and snow showers out of the fcst for 
Friday, but 12Z EC now has something, more in line with the 
GFS. Thus left mention in the fcst of some rain and snow.

I did cut back some on the rain and snow showers for Wed.
Given northwest flow, models show much of the snow showers
just falling apart as they move into central PA.

&&

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
Some late afternoon TAF updates, as CIGS continue to lower.

Still some fzra at JST, but near back edge of small patch
of rain northeast of the main area well to the southeast
and southwest of PA.

Temperature near 32 degrees at UNV, so added in zome fzra
until 00Z.

Earlier discussion below.

Lingering VFR will continue to trend to MVFR/IFR as the
afternoon progresses and the rain/drizzle keeps spreading 
north. Pockets of freezing rain or drizzle will be possible over
the higher elevation terminals in the Laurels through at least 
early evening.

A period of steadier/moderate rain is expected for the second
half of the overnight into early Sunday morning out ahead of an
occluded front that will be moving into and eventually through
the flying area. LLWS is likely late tonight into Sunday 
morning before strong post-frontal wind gusts kick in by Sunday
afternoon. 

Outlook...

Sun...Scattered rain showers early, then strong FROPA/windshift.
Turning very windy with sfc gusts to 50KT from ~260 degrees. 
Crosswind impacts and moderate to severe turbulence possible 
during takeoff and FAP. MVFR/IFR conditions in snow showers 
likely western 1/3 into Sunday night.

Mon...MVFR/-shsn western 1/3 trending VFR. Windy with gusts to 
50KT from ~290 degrees in the morning, then gradually subsiding
winds west to east into Monday evening. Crosswind impacts and 
moderate to severe turbulence possible during takeoff and FAP.

Tue...No sig wx.

Wed...VFR/MVFR with chance of light rain/snow showers.

Thu...No sig wx.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from 1 PM Sunday to 1 PM EST Monday for 
PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-
049>053-056>059-063>066.
Winter Weather Advisory until 7 PM EST this evening for PAZ018-
024-025-033-034.

&&

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