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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

FXUS61 KCTP 231059

Area Forecast Discussion
National Weather Service State College PA
659 AM EDT Fri Aug 23 2019

A few weak waves of low pressure will ride east across the
southern tier of Pennsylvania this morning bringing widespread
clouds and occasional light to moderate intensity rain showers. 
A large area of high pressure over Lake Superior will drift 
gradually to the east, reaching northern New England on Sunday. 
This weather feature will bring us a several day string of dry 
and cooler weather with low humidity right into early next week.


Surface cold front lies just south of the Mason-Dixon Line early
today, but several distinct bands of 850-700 FGEN and associated
UVVEL (beneath the RE region of a 90-100 kt jet core over
Western and Northern New York) were found drifting east across 
the southern few layers of PA counties. Light to moderate rain 
bands were the result of this low to mid level forcing, and the
past several runs of the HRRR and HREFV2 maintain periods of
light to moderate rain/showers (falling from a thick
AS/high-based NS layer) across Scent PA and the Lower Susq 
Valley through much of the remainder of this morning. Lighter 
and more scattered showers could linger into the early 
afternoon hours to the south and east of the I-81/I-76 corridor.

Near and to the north of I-80, a mid-level OVC (with a few 
light showers possible across the Middle Susq Valley this 
morning), will transition into increasing amounts of sunshine 
this afternoon (filtered through a high cloud deck of Cirrus 
and Cirrostratus). 

A 2-3kft thick layer of high-based strato cu will likely advect
south into the northern mtns this afternoon and persist into 
this evening. 

Trimmed hourly and previous fcst high temps down by a few-svrl  
deg F across mainly the central and southern zones, where clouds
and or showers will linger the longest today. 

Max temps will range from the upper 60s across the northern mtns
and highest terrain of the Laurels, to the low and mid 70s
elsewhere in Central PA and the Susq Valley.


Dry and cooler conditions will occur tonight and Saturday as
high pressure advects an early fall-like, modified CP airmass SE
into the region. 

A large air/water delta T late tonight/early Saturday will
result in some patchy valley fog across the north. However, the
light northerly breeze should prevent it from getting dense in
most locations. 

Min temps early Sunday morning will be in the mid-upper 40s
across the north and lower to mid 50s over much of the south.

High temps will be about 1-3 deg F warmer in most areas
Saturday, and perhaps as much as 3-4 F higher throughout the
southern valleys.

p builds SE from 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.


For the 12Z TAFS, slowed down the clearing some for today.

Strong upper level jet just to the north is aiding in keeping
the rain going across the south.

Overall conditions not real bad across most of the area as of 
7 AM.

Expect slow improvement from north to south today, as high
pressure builds southward with drier air.

Most of the weekend and next Monday should be dry with VFR
conditions. Perhaps some early morning fog.


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




NEAR TERM...Lambert
SHORT TERM...Lambert
LONG TERM...Evanego