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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

                            
000
FXUS61 KCTP 222115
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
415 PM EST Fri Feb 22 2019

.SYNOPSIS...
Fair weather will hold through tonight thanks to high pressure 
tracking north of the region. The high will move off the 
Southern New England Coast on Saturday, and a gusty southeast to
south wind will develop with clouds thickening up during the 
day followed by rain late Saturday into early Sunday. The air 
could be cold enough late Saturday afternoon and evening 
throughout the valleys of Central Pennsylvania for the rain to 
begin as a brief period of freezing rain.

Gusty and potentially damaging westerly wind gusts will develop 
in the wake of cold front late Sunday morning and will continue 
through Midday Monday.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Varying amounts of high clouds streaming overhead across central
PA this afternoon, while thicker mid cloud covers the south, 
and mostly sunny conditions are over the north. This should 
continue to be the case through evening as the high provides a 
drier flow to areas north of I80.

Skies will be clear to partly cloudy across Central and 
Northern PA tonight, while thickening mid and high clouds 
build across the southern few layers of PA counties. 

Lows will be cool (in the upper teens throughout the perennial 
cold spots up north, to around 30F in the south thanks to the 
cloud cover), but still a few deg F above normal in many 
locations.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
Main story for Saturday PM and beyond into Sunday is for a
soaking rainfall for most of central PA. PWs will jump upward 
to moderately high levels (0.75 to one inch) during the mid to 
late morning hours Sat across the SW third of PA, and during the
afternoon hours central and NEPA.


Clouds increase and thicken during the day with rain spreading 
in from the south/southwest early Sat afternoon acrs the Laurel 
Highlands, and during the mid to late afternoon hours elsewhere 
as a neg tilt 850-700 mb trough moves northeast. Precip is
delayed a few hours from previous solutions, which decreases the
already marginal chc of fzra over PA. Best chance for spotty
glaze at the onset of rainfall is over the Laurel Highlands
where POPs increase soonest Saturday morning. Farther north a
few more hours of warming should keep valleys plain rain with
just a few ridgetops seeing patchy fzra at the onset. No
headlines at this time given the low end threat.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Higher PWAT air (between 1-1.25 inches) will spread in from the
Ohio River Valley Saturday night and a soaking rainfall for 7 to
9 hours will ensue as uvvel increases at the nose of a 55 to 65
kt swrly LLJ. Consensus rainfall amounts are between 0.6 and 1.0
inch by around sunrise Sunday, which should be very manageable
regarding stream levels since a significant percentage of the 
snow from the midweek storm melted on Thursday, and most will be
gone and flowing into the larger tribs and rivers before the
bulk of the rain arrives late Saturday into early Sunday.

Focus shifts toward the potential of strong winds Sunday PM, as
trailing cold front sweeps through the area, allowing strong 
winds associated with Grt Lks storm to mix to ground level. This
scenario of a powerful low passing north of Pa fits the pattern
we see with our strongest winds across central Pa and a quick 
look at model 850mb winds suggest >50kt gusts are possible.

High Wind Watch for our Entire Area from Late Morning Sunday 
into Monday afternoon, with strongest winds over the west
several hours before they expand into eastern areas.

As the Temperatures continue to warm aloft, expect a likely 
surge to springlike readings Sunday. The shallow cool air should
mix out then there should be a return to seasonal readings for 
next week. 

Med range guidance points toward dry weather early next week, 
as high pressure builds across the region. However, model spread
and forecast uncertainty ramps up by the middle of next week 
concerning the track, timing and strength of a fast moving 
shortwave approaching from the midwest. Given when the 
instability is for the storm next midweek, have changed precip 
type to mostly snow.

GFS forecasting potential for another system next weekend, with 
ECMWF developing a weaker coastal low by Sunday. Much
uncertainty through this portion of the forecast so low
confidence equals low pops.

&&

.AVIATION /21Z FRIDAY THROUGH WEDNESDAY/...
VFR flying will continue over the next 24 hours with sct-bkn
high clouds and light/variable winds. Clouds and moisture
increase on Saturday with rain spreading south to north. Slgt
chc of patchy freezing rain at the onset over the Laurel
Highlands.

Outlook...

Sat...Trending MVFR to IFR with rain spreading south to north. 

Sun...Windy with showers. Some snow showers possible late 
across the northwest. 

Mon...Windy. Mainly VFR. Still a chance of snow showers across 
the northwest.

Tue...Mainly VFR. Chc of snow late across the northwest.

Wed...MVFR with chc of flurries.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from Sunday afternoon through Monday afternoon 
for PAZ028-036-037-041-042-046-049>053-056>059-063>066.
High Wind Watch from Sunday morning through Monday afternoon 
for PAZ004>006-010>012-017>019-024>027-033>035-045.

&&

$$
SYNOPSIS...Lambert
NEAR TERM...DeVoir/Lambert
SHORT TERM...DeVoir/Lambert
LONG TERM...Lambert/RXR
AVIATION...DeVoir/Steinbugl