386 
fxus61 kctp 201146 
afdctp 


Area forecast discussion 
National Weather Service State College PA 
746 am EDT sun Jul 20 2008 


Synopsis... 
low pressure...located over Wisconsin this morning...will track 
east across upstate New York early Monday...pushing a cold front 
into Pennsylvania. The cold front will likely stall out over 
Pennsylvania until Canadian high pressure builds into the region 
late Tuesday. High pressure will slowly push off the East Coast by 
late in the week...allowing a cold front to approach from the 
Great Lakes. 


&& 


Near term /until 6 PM this evening/... 
early am water vapor loop shows one shortwave and associated 
convection pushing through southern Ontario...an mesoscale convective vortex associated 
west/dying mesoscale convective system over the Midwest...and a potent shortwave over the 
northern plains. 


Radar trends indicate scattered showers/thunderstorms likely through the morning 
hours over the northern mountains...as S Ontario shortwave passes north 
of PA. By afternoon...heating of blyr results in ens mean convective available potential energy over 
1500 j/kg across western PA. Approach of mesoscale convective vortex likely to result in a 
good chance of thunderstorms...especially northern PA. Have leaned toward the 
higher met probability of precipitation based on 03z sref. Entire region currently under 
a slght risk of severe weather late today. However...latest model data 
suggests greatest risk is over the north mountains closest to middle level wind 
maximum/best shear. 


Clouds and potential showers early today should result in somewhat 
cooler temperatures than recent days over the north today. However...heat 
likely to continue unabated over southern/central PA...where a 
good deal of sunshine expected. 


&& 


Short term /6 PM this evening through 6 PM Monday/... 
potent shortwave...currently over the North Plains...will track north 
of PA early Monday...pushing a dying cold front through central PA. 
Sref data suggests best chance of showers will be early Monday over 
northeast PA with frontal passage...then over southwest PA by afternoon...as wave 
forms on stalled frontal boundary across the Ohio Valley. 


&& 


Long term /Monday night through Saturday/... 
with stalled frontal boundary in the vicinity of PA...will keep chance 
of showers in the forecast through Tuesday. Much drier air likely to 
overspread the region Tuesday night through Friday...as Canadian hi pressure 
builds southeast into PA. Latest gefs data indicates a high likelihood of 
dry weather Wednesday and Thursday. 


With surface high overhead and anomalous precipitable water values...expect much 
cooler nights with at or below seasonal readings. Gefs 850 temperatures near 15c suggest 
seasonal daytime highs. Will reintroduce chance probability of precipitation by late Friday...when 
a cold front may approach from Great Lakes. 


&& 


Aviation /12z Sunday through Thursday/... 
mainly MVFR to IFR visibilities across central PA again this morning in 
fog/hz. This will mix out to a 5-7sm visibility day with VFR clouds. 
Initial wave sliding across New York state spreading a line of showers 
into west PA. This will weaken as it moves eastward and affect mainly 
kbfd. Later today heating will kick convection off 
anew...spreading from northwest to southeast as the day wears on...although 
highest probability of precipitation remain in the northwest. 


Frontal boundary will sag in from the north and linger across the 
region posssibly into Tuesday...keeping weather unsettled 
especially in the afternoon Monday and Tuesday. The soup will continue 
south of the boundary as dewpoints remain high...keeping haze/fog 
around especially from evening through middle morning...but the rest 
of the time will be predominantly VFR with local restrictions from 
storms. Eventually by midweek some drier air will move in on northwest 
flow. 


&& 


Ctp watches/warnings/advisories... 
none. 


&& 


$$ 
Synopsis...Fitzgerald 
near term...Fitzgerald 
short term...Fitzgerald 
long term...Fitzgerald 
aviation...rxr