266 
fxus61 kctp 231234 
afdctp 


Area forecast discussion 
National Weather Service State College PA 
734 am EST Monday Nov 23 2009 


Synopsis... 
low pressure system will pass south of Pennsylvania 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/... 
surface hi pressure passing off the new eng coast combined with weak surface low 
off the southeast coast resulting in moist...anomalous easterly 
flow over the middle Atlantic region. Area of rain currently working 
northward across Virginia is likely to dwindle today as associated 
shortwave weakens and moves into low precipitable water air mass currently in 
place over PA. Will therefore Reserve highest chance of light rain/dz 
for the southern tier counties late this afternoon. 


11-3.9 micron satellite imagery already showing fairly extensive 
stratocu layer at this hour...which should persist throughout the 
day...keeping temperatures from rising out of the 40s over most of the 
region. Latest sref mean quantitative precipitation forecast this afternoon ranging from zero over the 
north...to around 0.10 inches in the south. 


&& 


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 /12z Monday through Friday/... 
middle-level moisture will continue to move in from the south spreading 
MVFR ceilings across much of central PA this morning. Ceilings will lift a 
bit late morning into this afternoon which could bring a period of 
VFR ceilings...but by late afternoon ceilings will again be on the 
decrease from S to north with a return to MVFR and then to IFR 
tonight. Precipitation will remain south of PA airfields until closer to 
00-06z Tuesday. Jst/aoo/unv could see isolated rain showers between 20-24z...however 
overall higher confidence in vcsh for most sites until later 
tonight. 


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...Fitzgerald 
near term...Fitzgerald 
short term...Fitzgerald 
long term...Fitzgerald/Martin 
aviation...rxr