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FXUS61 KCTP 221930

Area Forecast Discussion
National Weather Service State College PA
330 PM EDT Thu Aug 22 2019

A cold front will push through the state this evening, bringing
fairly widespread showers and scattered thunderstorms. Cooler 
and much less humid air will move in for Friday and will last 
through the weekend.


Cold front now runs from near KFIG (Clearfield) to KN38 
(Wellsboro). The wind has turned due north over the nrn
counties. A patch of --RA is moving into the far NW, well behind
the front. It should dry up slowly as it moves into our CWA. 

The current radar trends show the showers struggling to overcome
some slight warming aloft. The tallest clouds are along and just
S of the front. However, the vort max is now into SWrn PA, and
additional tall showers are cranking up over SWrn PA. This is a
good idea of what will happen through the rest of the aftn and 
evening - development of TSRA as the instability rises. Shear
still 30-40KTs, but CAPE limited thus far. Still expect the CAPE
to get big in the SE, but it could stay (well) below 1000J for
other places. Still some threat for showers to pass over the
same areas which could make an isolated flooding report.

Expect the storms to sink south of the area as they die off in
the mid-evening. All should be quiet by 10-11 PM in the far SE.
Clearing across the north may be followed by some lower clouds
later at night. But, fog is also possible in many places, esp in
the northern valleys if it stays more-clear, and anywhere the
rain stops and it clears out immediately after. Many places will
have mid-high clouds overhead for much of the night, though.
Expect some sprinkles to hang on through the night along and
south of route 22/PA Turnpike. 

Mins will get down to 50F or lower in the north due to the
clearing. If lows clouds come back, it would not be so cold and
temps may even rise before sunrise there. Mins will still be in
the 60s over the SE half of the area.


The front is still progged to stall out 100mi or so south of the
Mason-Dixon line. But, much drier air will spread through all
the area and bring dry and cooler conditions for Friday (and all
the weekend). Any early fog (and/or sprinkles in the south) will
dissipate soon after sunrise. Maxes will hold in the 60s over
the highest hill tops but still get into the u70s in the larger
cities of the Susq valley.


An extensive area of high pressure will bring fair and dry 
weather to central PA this weekend. Weekend temperatures should
be near to slightly below normal for late-August, with a dry 
airmass providing pleasantly warm afternoons and comfortable 

Heading into next week, the question will be how quickly return
flow develops and brings moisture back into the area. The GFS 
continues to be a bit more bullish, bringing showers back into 
the region Monday, while the ECMWF delays the wet weather until
Tuesday. Given the uncertainty, went with a model blend and 
gradually increase PoPs Monday into Tuesday. PoPs should peak 
Wednesday with a frontal passage, with a drying trend for the 
later part of next week.

The temperature forecast becomes less certain early next week, 
as models develop southeasterly low-level flow that may advect 
clouds into the area and result in lower high temps Monday and 
Tuesday. Following the mid-week frontal passage, cooler and 
drier weather should return late next week.


A west-east cold front has sunk southward to almost I-80 in the
west, but hanging on in about 20nmi north of KIPT. Anywhere
south of the front could see TSRA this aftn and early evening. 

The highest chc of TS is along I-80 thru 20Z, but the chcs
increase for the srn half of the area almost all at the same
time. The worst of the storms will likely hold off until after
22Z in MDT and LNS, but the threat there will be over there by 
03Z as the front will have passed thru before then. Some patchy
light rain is possible overnight for any of the southern 
terminals (KJST- KAOO- KMDT- KLNS). A little fog is possible, 
too, mainly in the far nrn valleys and anywhere the sky clears 
right after the rain ends. 

After a possible sprinkle early Friday in the srn terminals, it
should be dry weather with mostly VFR conditions all weekend. 
Morning valley fog is almost a given for each morning throughout
the weekend across the north. Some fog could also creep into 
the central and SErn valleys if it gets cold enough. 


Sat-Sun...AM fog possible. 
Mon...AM fog possible. SE low level flow, low clouds poss. 
Tue...SHRA poss.





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