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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

FXUS61 KCTP 180313

Area Forecast Discussion
National Weather Service State College PA
1113 PM EDT Fri May 17 2019

A weak cold front overhead will push south and to near the MD
border by morning, then try to return north as a warm front on 
Saturday. Low pressure will track north of Pennsylvania Monday, 
as its trailing cold front comes through the state.


The air is drying slightly from N-S and we have not seen any fog
so far. Mid clouds sliding in from the west could keep any fog,
esp valley fog in the W, from forming. But, these might not get
into the far northern and northeastern counties. Will have to
keep an eye on this, but a widespread dense fog is not expected.
Will add a little mention into the NE, though since they did
have rain in many places and the dewpoint hasn't been going down
too quickly as of yet.

Rest of the fcst is rolling along. Showers over the SW may
linger, but will likely take a break for a few hours. No heavy
rain and little if any ltg now. 

Heating waning and the showers, esp those across the nrn
territories (of PA) are almost gone. The only CAPE left is over
SWrn PA, and even those showers have only produced sporadic 
cloud flashes and perhaps only 1-2 CGs. Expect those to remain 
more- steady state, though, this evening as the short wave 
energy rolls overhead there. However, they, too continue to inch
southward. Much of the night will be dry over 90% of the CWA. 
Keeping just a low PoP along the MD border, and in the far west 
near sunrise. Much drier air (~50F dewpoints already and 40s 
overnight) moving in from the north. However, clearing may take 
a while, and may self-destruct (fog) in those places that did 
receive rain late today. Will hold off on mentions of fog for 
the time being. If it clears as expected, mins could touch 40F 
in the nrn valleys.


The frontal boundary will return as a warm front pushing north
on the region Saturday. Heating of warm, humid air mass south 
of this boundary will likely result in scattered diurnally- 
driven convection, focused mainly along the spine of the 
Appalachians in the afternoon and evening.


Rising heights and building upper level ridging will spell a 
warmer and more humid sensible wx trend Sunday-Monday. While 
there will be plenty of dry breaks, we still cannot rule out a 
few spotty showers or isolated t-storm during this time. Expect 
sparse coverage with limited rainfall. 

Medium range guidance lends increasing confidence in a period 
of dry/cooler weather Tuesday, as high pressure and low pwat air
mass builds southeast into the area. 00Z NAEFS indicates 
Pennsylvania will be on the northern periphery of a building 
subtropical ridge the second half of next week. Shortwave riding
over the top of the ridge will bring back the chance of showers
both Wednesday and Thursday. This potential will likely continue
into Friday as a nearby boundary on Thursday will lift back
north through the region.


Spotty showers should continue to dissipate overnight. KJST and
KBFD are already seeing some fog begin to form, and model 
guidance suggests that they will both dip to IFR conditions 
during the pre-dawn hours.

Low vsbys and cigs across the western highlands will begin to 
improve towards or shortly after after daybreak on Saturday. 
A weak frontal boundary will sit just to our south on Saturday,
and a few shra/tsra could pop up across mainly southwestern PA.


Sat...AM low cigs and vsbys western highlands. Isolated aftn 
shra/tsra possible over mainly SW PA.

Sun...Scattered aftn shra/tsra possible area-wide.

Mon...AM low cigs possible. Scattered aftn tsra impacts 
possible eastern PA.

Tue-Wed...Mainly VFR.




NEAR TERM...Dangelo
SHORT TERM...Fitzgerald/Lambert/Colbert
LONG TERM...Fitzgerald/Gartner