Tuesday, May 21, 2019, 2:51 PM EDT
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Area Forecast Discussion
Valid At
Wed, Dec 31, 7:00pm EST
FXUS61 KCTP 211639

Area Forecast Discussion
National Weather Service State College PA
1239 PM EDT Tue May 21 2019

A ridge of high pressure will build east across the Commonwealth 
tonight and slide off the Mid Atlantic Coast by Wednesday 
evening. Fair weather will prevail through Wednesday afternoon,
but much higher humidity will surge into the state from the 
Ohio Valley Wednesday night and Thursday, bringing an increasing
chance for showers and Thunderstorms. Pennsylvania will be on 
the northern periphery of a building subtropical ridge late this
week and over the upcoming weekend. This will mean occasional 
bouts of mainly afternoon and evening showers and thunderstorms.


Scattered to broken mainly thin high cloud remnants from 
overnight and early morning midwestern convective clusters are 
streaming across parts of western and central PA this afternoon.
A breisk north to northwest flow is making temperatures in the 
50s and 60s feel much cooler, but at least it's fair and 
pleasantly cool. Seeing gusts in the teens and lower 20s thanks 
to rather efficient 3-5k AGL mixing height. 

Expect to see better decoupling tonight as sfc high builds into
the region. Winds will become light after 00z, and given still 
dry air over much of the CWA, expect similar, if not cooler min 
temps early Wednesday morning. We saw local mid 30 readings over
Warren and McKean Counties this morning, so will mention patchy
frost there as most areas should remain in the upper 30s for 
lows. Official growing season began in these areas today. Min 
temps at sunrise Wed will generally vary from the upper 30s in 
the perennial cold spots of the north, to around 50F in the 
larger metro areas of the southeast, but we could again see
highly localized mid 30s in the coldest spots.


After a fair tranquil and cool start with high pressure
overhead, southeasterly llvl flow will increase during the day 
as the high pressure ridge drifts off the NJ Coast. Several 
layers of clouds will also form/advect east into region as the 
nose of much higher PWAT air (30-35mm or +2-3 sigma) spreads 
into Western PA late in the day. A small chc for showers exists 
across the northern tier and Alleghenies of west-central PA 
later in the afternoon and evening Wednesday, and kept low chc
POPs in the forecast for the NW Mountains as a result. Highs
will moderate into the upper 60s and 70s throughout with a 
noticeable uptick in humidity in the afternoon as dewpoints 
rise through the 60s.


00Z NAEFS indicates Pennsylvania will be on the northern 
periphery of a building subtropical ridge late this week into 
next weekend. 

A much higher chc for SHRA/TSRA will develop late Wed night and
early Thursday, associated with an area of +2-3 sigma 850 mb 
moisture flux (as depicted by the latest - 00Z GEFS) that will 
spread east across the CWA accompanied by elevated instability 
and 850 mb LIs dipping t between -2 and -4C.

Pops were nudged up into the high chc to low likely range
Wednesday night/early Thursday. 

Shortwaves riding over the top of the aforementioned ridge will
bring back the daily chance of convection. However, bulk of med
range guidance supports a brief period of fair weather Friday, 
as drier air builds in behind a Thursday PM cold front.


A ridge of high pressure will build east across the Commonwealth 
today and slide off the Mid Atlantic Coast Wednesday evening. 
VFR expected over all routes today and tonight. NW winds will 
persist at 10-15 mph with gusts around 20 mph before diminishing
by sunset. VFR conds prevail tonight and Wednesday, with winds
shifting to the southeast and increasing later Wednesday
morning afternoon.


Tue-Wed...Mainly VFR.

Thu...VFR into the afternoon, then strong thunderstorms possible
mid afternoon into Thu night.

Fri...Ceiling restrictions poss NW early, then mainly VFR.

Sat...scattered restrictions possible from potential showers 
and thunderstorms.




SHORT TERM...Lambert
LONG TERM...Lambert/Gartner

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