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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

                            
000
FXUS61 KCTP 202317
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
717 PM EDT Wed Mar 20 2019

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

A frontal system approaching from the west and a coastal low 
sliding north along the Atlantic Seaboard will bring inclement 
weather starting late tonight into Friday. High pressure will 
return for the weekend, with warmer temperatures Sunday into
Monday.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Clouds increasing this evening as high pressure continues to
exit the New England Coast and weather deterioriates
accordingly. Central PA will find itself between an approaching
cold front moving through the Great Lakes and a developing 
storm system lifting northward across the the Mid Atlantic 
states tonight and Thursday. The coastal system will be the 
bigger weather maker, spreading a lowering cloud deck into the 
region overnight with light rain developing mainly over eastern 
sections late. The models are better locked onto this low 
pressure area after transitioning its track westward over the 
last couple of runs. A period of moderate rain is expected over 
the eastern portions on Thursday.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
The weather will begin to deteriorate tonight as we get pinched
between an approaching cold front moving through the Great 
Lakes and a developing storm system lifting northward across the
the Mid Atlantic states.

The southern system will be the bigger weather maker bringing a
soaking 1 to locally up to 2 inches of rain over about the SERN
1/3 of the forecast area from sunrise through early Thursday
night. The NAM/ECMWF/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. No
accums are expected.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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 
Laurels.

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.

&&

.AVIATION /23Z WEDNESDAY THROUGH MONDAY/...
No big changes for the 00Z TAFS.

Made some minor adjustments to the winds.

Earlier discussion below.

Still VFR conditions across the area.

Two areas of showers, one across the western Ohio Valley, and
another small area into southeast VA.

Expect far western areas and southeast areas to see MVFR and 
IFR conditions first late tonight into Thursday.

For the late afternoon update, made a few minor changes. 

I will use these on the 00Z TAF package.

More information below.

High pressure will continue to move away from the southern New 
England coast through tonight. Southerly winds around 10 mph 
with intermittent gusts to 15-20 mph will diminish by sunset as
thin high clouds fill the sky under widespread VFR conditions.

The weather will begin to deteriorate tonight as we get pinched
between an approaching cold front moving through the Great 
Lakes and a developing storm system lifting northward across the 
the Mid Atlantic states. The coastal system will be the bigger
weather maker, developing an MVFR cloud deck that will lower to
IFR by early Friday, initially in the Lower Susq but spreading
into the central mountains. Rain will also lower vsbys with most
intense rain over the SE. The higher elevations could have 
snowfall or at least rain mixed with snow later tonight and 
early Thurs. 

Improving conditions over the SE half late Thu night into Fri,
but another shortwave dropping across the Great Lakes will
reinforce cloud restrictions over the NW half and bring
scattered snow showers to the higher terrain as well.

.Outlook...

Thu...RA SE, RA/SN NW. +RA poss SE. IFR SE half, MVFR NW half. 

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

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

Sun-Mon...No sig wx.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...RXR
NEAR TERM...DeVoir/RXR
SHORT TERM...RXR
LONG TERM...Dangelo/La Corte/Gartner
AVIATION...Martin