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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

FXUS61 KCTP 211109

Area Forecast Discussion
National Weather Service State College PA
709 AM EDT Sun Apr 21 2019

A weakening upper low and associated cold air aloft will drift 
slowly east across the state today through tonight bringing more 
clouds and scattered showers, especially during the afternoon 
hours. Temperatures today will also be several degrees cooler 
than Saturday.  

A ridge of high pressure will build east from the Ohio Valley and 
provide us with fair, dry weather for much of Monday and Tuesday 
before a fast moving cold front brings a few showers or a 
thunderstorm late Tuesday or Tuesday night.  

Wednesday and Thursday should feature mainly dry conditions once
again under the influence of another area of high pressure.


Upper level trough axis was located over western PA early today
and will progress very slowly east across the CWA today before
becoming located over Eastern PA early Monday morning. 

Temps aloft will be cooling by a few to several deg C, which
will translate into daytime max temps anywhere from 6-12 deg F
cooler than Saturday's. 

Sfc based cape is minimal and under 200 j/kg at its peak today,
so isolated instability showers early today will increase in 
coverage to the scattered (30-50 percent) category during the 
late morning and afternoon hours. However, this convection will 
have notably lower tops and an inability to produce small hail 
that was prevalent in the stronger cells on Saturday.

Showers will once again diminish tonight and become quite 
isolated as llvl heating wanes.  

Min temps to start today will vary from the low to mid 40s
across the NW Mtns and Laurel Highlands to the low to mid 50s in
the Susquehanna Valley.

This afternoon's highs will be only in the low to mid 50s across
the higher terrain of the west where 850 mb temps will cool off
to plus 2-4C, while max temps in the mid 60s will be common
throughout the Susq Valley.


Morning clouds Monday, and perhaps a few stray showers drifting
south on the back side of the departing upper trough, will 
transition into a partly to mostly sunny afternoon with rainfree
conditions over all of the region (except for perhaps the 
Western Poconos and SE PA where a few showers will still be 

High temps Monday will increase by about 10 deg F over the west
and by 5 or 6 deg F in the east, ranging from the mid 60s across
the Mtns, to around 70F in the Susq Valley. The mercury will 
rise by another 5-8 Deg F in all areas for Tuesday under a ridge
of high pressure in the morning followed by increasing llvl 
warm advection and southwesterly flow in the afternoon. 
Widespread 70s will be found for highs on Tuesday and a few 80F 
readings are possible in the southern valleys.


There is decent model agreement in the next cold frontal system
moving through the area during the midweek period. Showers and 
poss a tstm impact mainly NW areas Tue night, with scattered 
light showers poss areawide early Wed. 

Beyond Wednesday, weak frontal boundary gets hung up south of
the region with a breezy, but mainly dry Wed in store. Models 
showing some divergence for late in the week, but trend looks 
to be a transition to SW flow. Looking like a chilly morning 
Thursday with dry air in place and light winds, with lows 
potentially dipping into the upper 30s in the valleys of the 
northern mountains.

A potent shortwave progged in around Friday will bring another 
shot for showers/tstms followed by dry, breezy and cooler to
start the weekend with another chilly morning Sat before
trending toward warmer temps on Sunday.


VFR conditions across much of central Pennsylvania airfields
this morning, but MVFR conditions exist across the northern and
western mountains. Isolated showers this morning will become
more numerous with daytime heating, with the upper low spinning
overhead. MVFR conditions at KBFD and KJST will be difficult to
break today, but thinking is that at least a brief period of VFR
conditions may develop even at these locations for a time this

Showers should end this evening, as the upper low slides east 
of the area. 


Mon...Morning MVFR ceilings possible N and W, otherwise VFR.

Tue...Mainly VFR. Scattered SHRA/TSRA possible far NW late.

Tue PM...Cold frontal passage, with accompanying SHRA/TSRA.

Wed-Thurs...Mainly VFR, but with scattered showers.




NEAR TERM...Lambert
SHORT TERM...Lambert
LONG TERM...Lambert/RXR/Steinbugl