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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

FXUS61 KCTP 170947

Area Forecast Discussion
National Weather Service State College PA
447 AM EST Sun Feb 17 2019

A fast flow aloft will keep the weather active through the week.
A weak disturbance will move across the region later Sunday and
Sunday night. A stronger storm will approach for the middle of 
next week. A third storm is possible at the end of the week.


Generally clear skies have allowed temps to cool off into the
teens N and W. High pressure will be retreating very quickly to
the NE today as low pressure will move up the Ohio Valley. Warm
advection will trigger precip of all types to start up late
today in the west. Continuity is high with the forecast, so
confidence is fairly high. The precip type is the big forecast
trouble. But, that has also been fairly consistent in model
progs the last few days. Maxes today will be highest over the
east, where the clouds arrive latest. Almost no guidance has
precip any farther east than route 219 by 21Z. But it does
spread over the area quickly this evening. 


Snow will be the initial precip type in most places, but it
could turn to sleet quickly everywhere south of I-80. The snow
will last longest over the nrn mtns. The temps warm aloft as the
low moves into the CWA, and most places will turn to a freezing
rain/drizzle after the best lift moves off to the north. SLRs 
will be 12-13:1 at first over the north, but drop below 10:1 by 
midnight. The QPF is not very heavy, but the duration of the 
snow in the north will likely lead to 2-4 inches there by the 
middle of the night. Elsewhere, the sleet will keep numbers 
down, but may still make a mess. The threat of FZRA/DZ is 
highest over the Laurels. But, again, the QPF is <= 0.25", so 
ice accums will likely not get into warning amounts since not 
all of it will be FZRA.

Temps remain very constant overnight...near freezing in much of
the area. The Laurels could get >32F later in the storm, but the
E/SE flow in place for most of the night doesn't give up the 
cold air very easily. 

As the low moves into NY, a small low may form over the
DelMarVA, and briefly hang precip up in the SE. But, temps will
also be warming after daybreak, and much of the area will be out
of the threat of FZDZ by 10 am. The temps will get cold enough
over the NW half to make anything left over into snow showers.
The downslope in the wake of the low will make it mild in the
SE, and help to break up the clouds there. The west wind could 
gust into the 30s in the southern tier in the afternoon. 


Monday night and Tuesday, expansive surface high pressure will 
expand from central/eastern Canada into the northeastern states,
with dry and seasonably chilly weather.

Current indications still are that another wintry mix event will
affect the Commonwealth from later Tuesday night through
Wednesday, with a snow to sleet/freezing rain to perhaps rain
transition anticipated. Stay tuned for the latest forecasts, as
specific details become clearer over time. 

Overall, our weather should dry out Thursday and Friday, as the
previous system lifts away to our northeast. Cyclonic W-NW flow
could bring some light rain or snow showers, but they look
inconsequential at this early juncture. 

Current model consensus points to a deepening storm system 
lifting northward through the Great Lakes/upper Midwestern 
states. Such a storm track would be likely to ultimately bring 
rain and milder temperatures. However, an initial wintry mix 
still appears possible prior to that. Once again, uncertainty is
high this far out, so stay tuned for later details.


Late evening satellite imagery showing clear skies across much 
of central Pa. However, MVFR stratocu remains trapped beneath 
inversion across the northwest part of the state. High pressure
will build into the area tonight, resulting in a diminishing 
breeze and likely causing the lingering stratocu to break up 
over northwest Pa. 

Excellent flying conditions are expected Sunday morning.
However, expect deteriorating conditions during the afternoon
and evening, as an approaching storm spreads a light wintry mix
and lowering cigs across the region. Latest model output 
supports widespread IFR conditions by late Sunday evening. 


Mon...AM low cigs possible. 

Tue...No sig wx expected.

Wed...Wintry mix possible. 

Thu...AM wintry mix/low cigs possible.


Winter Weather Advisory from 4 PM this afternoon to 1 PM EST 
Monday for PAZ004>006-010>012-037-041-042.
Winter Weather Advisory from 4 PM this afternoon to 10 AM EST 
Monday for PAZ017>019-045-046.
Winter Weather Advisory from 7 PM this evening to 10 AM EST 
Monday for PAZ027-028-049>053-056>059-063>066.
Winter Weather Advisory from 1 PM this afternoon to 10 AM EST 
Monday for PAZ024>026-033>036.


NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...Jurewicz