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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

                            
000
FXUS61 KCTP 202308
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
608 PM EST Wed Feb 20 2019

.SYNOPSIS...
A winter storm that brought snow to the region today will
transition to a period of light to moderate freezing rain this 
evening, keeping travel difficult across central Pennsylvania 
through the overnight. Conditions will improve into Thursday as 
a breezy west wind directs drier air into the region. Fair 
weather will continue into Friday before another round of 
precipitation over the weekend. It will turn windy and colder 
Sunday night into Monday with little to no precipitation 
expected early next week.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
*Winter storm impacts transitioning to ice accumulation this
 evening*
 
After several hours of robust isentropic lift/theta-e advection
generated a burst of moderate to heavy snow across southern
third of the CWA (and lighter amounts as one moves northward),
the accumulating snow portion of this event has ended as notable
"dry slot" as raced across the region transitioning 
precipitation from heavy snow over to mainly light freezing 
rain.

Another wave sliding quickly up the Ohio River from IN/KY will
bring a renewed round of precipitation in the form of freezing 
rain this evening transitioning to plain rain over western and
southern sections before precip ends after midnight. QPFs 
fairly impressive with convective look of this wave, with WPC
also promoting potential for up to 0.25" of ice accretion over
much of eastern third of CWA. So held on to ongoing
warnings/advisories through tonight. 

Precip intensity will decrease btwn 06-09Z with west wind shift
drying things out east of the Alleghenies. The shift to upslope
flow favors very light QPF/drizzle over the western ridges into
the predawn hours Thursday. Temperatures will slowly climb 
above freezing overnight by 12Z Thursday.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/...
Precipitation will be over by sunrise Thursday, but pockets of
icy conditions may persist through the morning rush hour -
mainly over the NE portion of the CWA and on untreated surfaces
until temperatures rise above freezing areawide by mid morning.

Breezy and dry wx expected on Thursday with temps rebounding
into the 40s. High pressure returns Thu night into Friday
bringing fair and dry weather. 

Another shot of WAA precip into a retreating cold sector 
with departing sfc high pressure is likely heading into the 
weekend. Timing will be important with a period of snow or ice to
start the weekend over south-central PA.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
The mid range models are in fair agreement through the weekend.
A fairly strong high pressure will continue to build into the
early weekend before a closed low propagating through the 
central US moves through the region Saturday night into Sunday. 

The models disagree on the depth of he cold air but there will
be warm air aloft which should bring the possibility of mixed 
precipitation early Saturday. After that expect periods of rain
throughout the weekend. Temperatures will trend milder Saturday
into Sunday with fcst highs in the upper 40s north to near 60F 
in the LSV. 

It will turn windy and colder into early next week. Model
guidance suggest advisory level wind gusts are possible Sunday
night into Monday. The colder NW flow should produce snow
showers downwind of Lake Erie. Otherwise, the wx looks mainly
dry Monday and Tuesday.

&&

.AVIATION /22Z WEDNESDAY THROUGH MONDAY/...
23Z update...IFR to fuel alternate restrictions will be common 
through the overnight hours, due to lower ceilings and 
persistent precipitation. 

As for precipitation type, mean cloud layer temps have warmed to
support just super-cooled water droplets (NE half of PA) or 
plain liquid (SW third of the CWA), with a mixture in between
where the cloud layer between 3 KFT AGL and 10 KFT AGL was a few
deg C above freezing, while the lower portion of the cloud and
ground was still hovering up to a few Deg C below freezing. 

Therefore, the next batch of precipitation racing NE toward
Central PA and Western Mtn airfields will be mainly in the form
of light to moderate intensity freezing rain that will last in
any one location about 3-4 hours during the first half of
tonight, with about 2-4 tenths of an inch of Liquid Equivalent.

The Freezing Rain will taper to freezing drizzle for a few hours
late this evening before temperatures inch above freezing after
05Z-08z, and then we're left generally with patchy drizzle and 
light fog/mist.

Thursday morning, as drier air slowly works its way in,
conditions will improve with time. KMDT, KLNS, and KIPT should
be VFR by 14-16z, with MVFR at KUNV and KAOO. Upslope westerly
flow will keep lower conditions going longer at KJST and KBFD.

Gusty E-SE surface winds will continue into the early evening,
along with LLWS conditions, before diminishing somewhat and 
veering into the S this evening. Winds will become W-NW and 
increase Thursday morning. 

Outlook...

Thu night and Fri...Possible lingering lower ceilings at KBFD
and KJST, with VFR elsewhere.

Sat...Deteriorating conditions, with steadier rain or freezing 
rain developing.

Sun...Windy with at least scattered rain showers, and associated
restrictions.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM EST Thursday for PAZ004>006-
010>012-017>019-037-041-042-045-046-049>053-058.
Winter Storm Warning until 6 AM EST Thursday for PAZ024>028-
033>036-056-057-059-063>066.

&&

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