599 
fxus61 kctp 231719 
afdctp 


Area forecast discussion 
National Weather Service State College PA 
1219 PM EST Monday Nov 23 2009 


Synopsis... 


A weak wave of low pressure will pass off the eastern Seaboard 
tonight. A weak cold front will push into the region on 
Wednesday...followed by a more significant cold front Thursday. A 
rapidly strengthening storm off the northeast coast will likely 
produce cold and blustery conditions across Pennsylvania Friday 
and Saturday. 


&& 


Near term /until 6 PM this evening/... 


Moist southeasterly low level flow will continue into the 
overnight. Model soundings and satellite trends indicate that 
cloudcover will continue to increase and lower as the weak surface wave 
off to the south and the weak upper wave to the west both move toward 
the region. Precipitation is very spotty at this hour and there is little 
sign in the new guidance that it will amount to much more than 
that. Sref plumes show a large spread in the generally meager quantitative precipitation forecast 
output...pointing to just some occasional light rain or drizzle. 




&& 


Short term /6 PM this evening through 6 PM Tuesday/... 
have ramped up probability of precipitation tonight as easterly wind and precipitable water anomalies 
shift north into PA in conjunction with weak lg scale forcing 
ahead of shortwave approaching from the Midwest. Latest naefs 
epsgrams support likely probability of precipitation tonight over most of central 
PA...despite light quantitative precipitation forecast. Abundant ll moisture and cloud cover should 
hold temperatures well above seasonal norms tonight with mins near 40f. 


Ridging at surface and aloft should result in a dry Tuesday for most 
of the area. However...residual ll moisture trapped beneath 
subsidence inversion will likely keep skies cloudy. Despite lack of 
insolation...highs still likely to be above normal in this mild air 
mass. 00z naefs suggests highs mostly in the l/m50s. 


&& 


Long term /Tuesday night through Sunday/... 
a series of shortwaves prognosticated to carve out a deepening trough west 
of PA during the second half of the week. Initial shortwave will 
likely push a dying cold front through PA on Wednesday...accompanied 
by scattered rain showers. However...real cool down not likely until arrival of 
more significant front on Thursday. 


Deepening trough over the Midwest/Ohio Valley is likely to spawn a 
developing coastal low late this week...which could potentially 
affect central PA in the late Thursday/early Friday time frame. 
Latest naefs data support a chance of rain showers in association with cold 
front. However...more sig precipitation from coastal low is likely to 
fall north and east of PA. 


Fairly high confidence forecast Fri-Sat...as all model data showing 
deep trough shifting over the northeast Continental U.S.. looks like a good chance 
of lake effect snow showers over the alleghenies Fri/Sat...followed 
by more settled/milder conds late in the weekend with departure of 
upper low. 


&& 


Aviation /18z Monday through Saturday/... 


MVFR/IFR ceilings cover about the southwestern 2/3 or so of the forecast area and 
should continue to spread northward ahead of a weak trough of low 
pressure approaching from the Ohio Valley the rest of today and 
tonight. Spotty light rain or drizzle will also become a larger 
threat as time wears on...helping reduce viz to the 1-3 mile range 
on average later this evening and overnight. 


Outlook... 
Tuesday...MVFR/IFR ceilings. Rain showers in the am. 
Wednesday...MVFR to VFR. 
Thu-Fri...MVFR with chance -shrasn. 


&& 


Ctp watches/warnings/advisories... 
none. 


&& 


$$ 
Synopsis...la corte/Fitzgerald 
near term...la corte/Fitzgerald 
short term...Fitzgerald 
long term...Fitzgerald/Martin 
aviation...la corte