Preview of NWS' New Version of Forecast
This preview is not operational and should not be used for support decisions.

Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

FXUS61 KCTP 201203

Area Forecast Discussion
National Weather Service State College PA
803 AM EDT Wed Mar 20 2019

     Spring officially begins at 5:58PM today...

High pressure will assure fair weather into Wednesday. A 
frontal system approaching from the west and a coastal low 
sliding north along the Atlantic Seaboard will bring inclement 
weather Wednesday night into Friday. High pressure will return 
for the weekend.


A few thin high clouds are drifting across from the west, but
otherwise we are clear and chilly with a light wind. High
pressure off the southern New England coast will help establish
a southerly flow. Highs today will rise into the mid 40s to mid
50s from north to south. This will be a few deg above normal in
most areas.


The weather will begin to deteriorate this evening as we get
pinched between an approaching cold front moving through the Gr
Lakes and a developing storm system over the Mid Atlantic 

The southern system will be the bigger weather maker bringing a
soaking 1-2 inches of rain over about the SERN 1/3 of the
forecast area from tonight through the day tomorrow. The NAM was
the first model to catch onto this last night at this time, but
it differs tonight in that it is no longer stalling the low. 
The ECMWF and GFS all agree that the low will move up through 
the Chesapeake Thursday and into southern new England Thursday 
night. Ensembles indicate a respectable SLY low level jet 
develops and pushes a bubble of slightly above normal PWATs up 
along the coastal plain, but models keep things chugging along 
which will limit the QPF potential.

Meanwhile the cold front to the west is forecast to be absorbed
in the growing cyclonic circulation of the coastal system, the 
main effect will be to see colder air move in and maybe change 
the rain showers to wet snow showers over the NRN Mountains, 
as early as the evening hours. No accums are expected.


After the surface low moves off to our NE, a series of potent 
upper shortwaves will dive out of the upper Gr Lakes and lead to
a closed upper low moving down over NRN PA/SRN NY during the 
day Friday. A new shot of cold air will bring widespread 
cloudiness and snow showers over western and northern higher 
elevations, with a rain or a rain/snow mix over central and 
eastern areas. Accumulations will be on the light side, but a 
fresh coating to an inch or two of late season snow cannot be 
ruled out over the normal NW snow belts locations down into the 

Friday will also become breezy as the low deepens over New
England, with gusts to 30-40 mph possible. Highs in the 30s and
40s will feel much cooler.

High pressure will build in for the weekend with warmer days 
and cool nights. Temps will be remain below normal Friday and 
Saturday, but will warm significantly by Sunday and Monday.

By early next week big differences arise in the medium range
guidance. Both the ECMWF and GFS drive a cold front through the
area, with the GFS lagging the EC in timing as well as bringing
more precip compared to the ECMWF which makes for a mainly dry 
fropa. From there the GFS dries us out by Tuesday, while the EC 
gathers a significant storm uncomfortably close to our southern 
border. I tried to choose a middle ground POPs-wise, but the 
confidence after Sunday is pretty low overall.


For the 12Z updated drop in cigs and vsbys for the approach of 
a frontal system from the west and a separate coastal low 
sliding northward up the Atlantic Coast. This will put the 
squeeze on Central PA for Wednesday night and Thursday. Rain is 
likely everywhere, but the higher elevations could have snowfall
or at least rain mixed with snow later Wed night and early 
 MDT and LNS will see periods of rain after 09Z with MVFR cigs
and all southern and Eastern TAF sites with IFR possible at MDT
and LNS. 


Wed night...-SN/-RA NW. Rain poss by sunrise SE. Reductions to
MVFR likely NW, and poss SE.

Thu...RA SE, RA/SN NW. +RA poss SE. MVFR with IFR possible NW 
and SE, but mainly VFR central.

Fri...Becoming windy. AM low cigs/SHSN NW.

Sat...Gusty NW wind. Otherwise, no sig wx.

Sun...No sig wx.




NEAR TERM...La Corte
LONG TERM...Dangelo/La Corte