975 
fxus61 kctp 240025 
afdctp 


Area forecast discussion 
National Weather Service State College PA 
825 PM EDT Wednesday Jul 23 2008 


Synopsis... 
a slow moving cold front will move across the state tonight. 
Several waves of low pressure riding northward along the front 
will bring heavy rainfall of 2 inches or more to parts of eastern 
Pennsylvania. Improving conditions will occur Thursday as high 
pressure builds into the region. Friday will be warm and dry. 
Another cold front will approach the region this weekend with 
another round of showers and thunderstorms on Saturday. 


&& 


Near term /until 6 am Thursday morning/... 
00z surface analysis places surface trough over extreme southeast PA and 
cold front over western PA. Although radar still shows pretty good 
coverage of showers/thunderstorms over northwest mountains near upper low...will continue 
to place highest probability of precipitation across the southeast zones...where strong large 
scale forcing...favorable right entrance of jet and anomalous 
precipitable waters  all point toward the potential of locally heavy convective 
rainfall overnight. Latest radar loop also supports the idea of 
heavy rain potential late this evening and overnight. Flash flood 
guidance remains high across the lower susq valley...so no flood 
watches planned at this time...but smaller scale nuisance flooding 
seems likely from some of the locally heavy bands that manage to 
train along for any amount of time. 


Have lowered overnight probability of precipitation across the central mountains based on 
latest radar trends and 18z guidance. However...can/T rule out 
another shower/thunderstorm with passage of surface cold front later tonight. Have 
also added fog to the forecast...which seems all but certain given the 
recent rain...light wind and partial clearing expected. 


&& 


Short term /6 am Thursday morning through Friday night/... 
cold front should be exiting our area come Thursday morning. Both 
NAM and GFS say that precipitation should be east of our area after 12z 
Thursday. However the sref keeps a decent probability of precipitation 
Tom morning and therefore will leave in a chance across the far 
eastern zones. The upper level trough will still be to our west 
Thursday... meaning a chance of showers and an isolated 
thunderstorm will continue. The 700mb trough will slide just to 
our east which should act to cap US from widespread 
showers...however our northern and central counties should see a 
few showers. Even without any showers it should become mostly 
cloudy with mostly fair weather cumulus in the afternoon. 850mb 
temperatures of only near 12c and the mostly cloudy skies should keep 
highs of near 70 in the high terrain of the north to near 80 in 
the lower Susquehanna valley. 


Thursday night should see clearing skies and cool temperatures. 
Lows should fall around 5 degrees below normal across most areas. 


Friday should be a dry day with just some fair weather cumulus clouds. 
Expect more sunshine than on Thursday and slightly warmer 850mb 
temperatures near 13-14c. This should support highs about 5 degrees 
warmer than Thursday. 


Our next disturbance will approach the area Friday night in the 
form a shortwave ejecting out of the plains. This will likely be 
associated with an area of showers and thunderstorms well off to 
our west... but they should dissipate before reaching our County Warning Area. 
Therefore went dry for Friday night with just an increase in the cloud 
cover expected. 


&& 


Long term /Saturday through Wednesday/... 
not a lot of change from yesterday. Did edge probability of precipitation up some for 
Sunday and Sunday night...as the upper level trough moves across. 


Left Monday and Tuesday dry...and went with dry conditions for 
Wednesday. Expect northwest flow...and not ready to buy into blow up of 
feature on GFS. 


&& 


Aviation /00z Thursday through Monday/... 
areas of showers and thunderstorms continue this evening along a 
cold front moving through western Pennsylvania. Most of the sig 
convective activity is expected over northwestern mountains /kbfd/ and eastern 
part of district...kmdt and kipt. Behind the earlier and current storms 
a broken layer around fl100 will be common until widespread br 
sets up after sunset due to abundant low level moisture. Placed 
lower visibilities and ceilings in the airfields most prone to 
it...kjst...kipt and kmdt. 


The front should finally be offshore by Thursday morning bringing 
in VFR conditions. However we will still be under the upper level 
trough which may cause a few isolated afternoon showers to 
develop...which may briefly lower ceilings and visibilities to 
MVFR. VFR conditions expected Friday and Sunday... but yet another 
front may bring another chance of thunderstorms on Saturday. 


&& 


Ctp watches/warnings/advisories... 
none. 


&& 


$$ 
Synopsis...lacorte 
near term...Fitzgerald 
short term...chenard 
long term...Martin 
aviation...tyburski