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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

FXUS61 KCTP 182205

Area Forecast Discussion
National Weather Service State College PA
605 PM EDT Sun Aug 18 2019

It will remain very warm and humid into early this coming week 
and a meandering trough of low pressure will keep the mention of
mainly afternoon and evening showers and thunderstorms in the 
forecast. Cooler and much less humid air will arrive for 
Thursday through Saturday with dry conditions expected.


Scattered, mainly pulse-type convection continues to fire 
across central Pa early this evening. Capes over 2000 j/kg per
21Z SPC mesoanalysis will continue to support localized severe 
weather through around 01Z. However, weak deep layer shear 
should limit the threat of organized, widespread severe weather.

Expect convection to disspate after sunset. However, a 
weakening shortwave is progged to push into the region late 
tonight, so keeping low POPs in the forecast through the night, 
especially over the northwest counties. 

It will be another muggy overnight with lows ranging from the 
low 60s over the north to around 70F SE.


Scattered, diurnally-driven convection is expected again on Monday. 

A hot and humid day is on tap with heat indices around 100 for 
much central and SE PA. Scattered afternoon and evening showers 
and thunderstorms may knock some temps down but it will feel 
muggy. Moderate CAPEs in the 1000-2000J range could support a 
few strong storms, but fairly weak deep layer wind shear 
suggests little risk of organized severe weather. 

Model soundings indicate max temps will be a few deg warmer than
today, with highs ranging from the low 80s along the NY border
to the lower 90s in the valleys of southern PA. The combination
of heat and humidity may warrant the issuance of a Heat Advisory
for a few hours Monday afternoon.


Made some very small changes to this part of the package, given
not a lot of change on guidance and storms on the radar.

A trend toward cooler and drier weather is expected for the 
later part of the week, as a cold front moves east of the area.

Perhaps a shower toward the later part of the weekend.

More detail below.

Guidance continues to show a fairly vigorous upper trough 
crossing the northeast quadrant of the lower 48 this period. 
Within the upper trough, there are still smaller scale detail 
differences that will affect progression/speed of the leading 
surface cold front and will take more time to be resolved. The 
cold front will be a focus for convection as it pushes southeast
Wed-Thu. While predictability is too low and limited at this 
range, severe storm risk upgrades are possible into the short 

Late-summer heat episode continues into midweek with max temperature 
anomalies +5-10F above normal on Wednesday. At this time, expect 
Thursday to be the transition day with a relative cooling trend and 
push of drier air throttling temps back to near/slightly below avg. 
Friday into the weekend. Lower humidity will spell pleasant days and 
comfortably cool nights.


Brief restrictions will affect terminals in the path of the 
showers and thunderstorms into the evening. 

Abundant low level moisture, light winds and at least partial 
clearing should favor fog formation again late tonight into 
early Monday morning. 


Mon-Wed...Rounds of PM showers/thunderstorms. Late night and 
early morning fog/low clouds.

Thu...Trending VFR northwest; chance of t-storms southeast. 
FROPA Thursday night.

Fri...No Sig Wx.


Record max temperatures for August 19:

Harrisburg 97 in 1966
Williamsport 94 in 1899
Altoona 91 in 1983
Bradford 86 in 1978
State College 96 in 1899




NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/La Corte
LONG TERM...Martin/Steinbugl