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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

                            
000
FXUS61 KCTP 191802
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
202 PM EDT Tue Mar 19 2019

.SYNOPSIS...
High pressure will assure fair weather will last 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.

&&

.NEAR TERM /THROUGH TONIGHT/...
Cu field has expanded quite nicely and is fairly thick across
the nrn half of the CWA. The first cu of the day which popped
over Somerset Co did indeed mix out and also slide to the east
some. High pressure is almost overhead, and should be centered 
overhead tonight. The loss of heating this evening will lead to
the demise of the diurnal cu field. Some mid clouds may be found
over the north and cirrus may try to slide in as well. But, 
most of the night will be mainly clear. The fair skies and calm 
air mean good radiational cooling and will lead to seasonably 
chilly overnight with lows generally in the 20s.

&&

.SHORT TERM /WEDNESDAY/...
The surface high will move off the coast Wednesday. The
developing southerly wind on the western side of the anticyclone
will help push temperatures into the mid 40s to mid 50s. These 
numbers are pretty close to or even slightly above normal. Any
early high clouds could go away initially, but will likely 
increase/thicken from the west in the afternoon. Some cu may 
develop, too. The precip associated with the cold/occluded front
moving in from the west will likely stay off to the west until 
after sunset. 

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
A potent upper shortwave will drive a front through the Gr Lakes
Wednesday night and Thursday. This will increase the chances for
some rain by Thursday morning with periods of rain likely during
the day. 

At least a couple of complicating factors to consider going
forward:

First is the potential for some snow over the NW early Thursday
where we will start the day near or even below freezing. High 
temps will rebound into the 40s over the north so no sig 
accumulation is expected.

Second and potentially more important, the latest NAM and ECMWF
develop a potent low along the Mid Atlantic coast taking aim at
the SERN portion of the CWA with a significant QPF event. The 
NAM generates a widespread 2 to 3.5" of rain (snow?) with 1+ 
inches of QPF in the EC. The NAM even generates some heavy snow 
on the WRN edge of the precip shield in the marginally cold 
airmass. The ECMWF and ECENS have less rain and are not nearly 
as aggressive with the snow. At this stage I chose to use a 
blend of model POPs and downplayed the snow/QPF potential. 

A secondary cold front will cross the area Friday which will 
bring a reinforcing shot of colder air along with some late
season mountain snow showers.

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 Sunday climbing into the 
60s many areas through central PA and across the south. Warmer 
trend looks to last into the 8-14 day period.

Spring officially begins at 5:58PM on Wednesday 3/20.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Diurnal cu will evaporate this evening. High pressure should be
centered overhead tonight and will allow the wind to calm in 
all areas. VFR will continue through the TAF period and into 
early Wed night. But, the approach of a frontal system from the
west and a separate coastal low sliding northward up the
Atlantic Coast will put the squeeze on Central PA for Wed 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 Thurs. 

.Outlook...

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.

&&

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

&&

$$
SYNOPSIS...Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...La Corte
AVIATION...Dangelo