669 
fxus61 kpbz 230748 
afdpbz 


Area forecast discussion 
National Weather Service Pittsburgh PA 
248 am EST sun Nov 23 2008 


Synopsis... 
high pressure will cross the area today...bringing dry and not quite 
as cold conditions. A cold front will cross the region Monday...bringing 
widespread rain. Large low pressure will persist over the upper Ohio 
Valley from Monday night through Thanksgiving day...with significant 
snows possible. 


&& 


Near term /through tonight/... 
residual scattered snow showers/flurries have exited into central 
PA...with low clouds beginning to retreat. High pressure will 
continue to build across the region today...with the clearing trend 
continuing. With winds becoming southerly...temperatures will 
rise above freezing for all areas today...with middle 30s north 
to lower 40s across snow free areas of eastern Ohio/northern WV. 


Clouds will begin to increase tonight in advance of a cold front 
currently moving into the Central Plains. The clouds...along with 
continued southerly flow will keep temperatures 5-10 degrees 
milder than Saturday night...with low/middle 20s north to around 30 
across eastern Ohio. 


&& 


Short term /Monday through Wednesday night/... 
models continue to Show Low pressure intensifying over the 
Great Lakes...with a cold front sweeping across the area 
Monday. Initial precipitation is likely to begin across eastern 
Ohio Monday morning...and entering southwest PA and points 
east Monday afternoon. Timing of initial precipitation will be critical 
as thermal profiles suggest potential for freezing rain 
and/or snow early. Think eastern Ohio will have the greatest 
threat for freezing precipitation...but coverage will be limited 
with initial moisture falling into drier air. Will use slight 
chance of freezing rain for the western portions of eastern Ohio 
early Monday morning before quickly changing over to all rain...as 
the surface low is prognosticated to cross well to the north. Further 
east...think surface temperatures will warm before initial precipitation 
arrives...so will use mainly liquid precipitation Monday. Pop wise...will 
use categorical probability of precipitation area wide by Monday afternoon. 


The cold front will complete its passage across the area Monday 
evening...with precipitation changing over to snow. Models continue 
to indicate upper level low pressure to slowly cross the area 
then stall out across upstate New York through Wednesday. Track will be 
critical as possible dry slot could limit snow accums...but this 
scenario could yield significant snows for northwest PA and the 
ridges...with accumulating snows area wide. Will highlight the 
threat in the hazardous weather outlook...with watches/warnings 
and/or advisories possible in the next 24 hours. Snow showers 
will begin to gradually diminish Wednesday night as the low 
begins to depart. 


&& 


Long term /Thursday through Saturday/... 
scattered snow showers will persist Thanksgiving day...especially 
north as the low is prognosticated to exit into New England. Mainly 
dry conditions are expected on Friday...with the next system 
bringing a chance of rain/snow showers Saturday. Temperatures 
will remain below normal. 


&& 


Aviation /07z Sunday through Thursday/... 
high pressure covering the Ohio Valley today will bring VFR conditions 
through Monday morning. Low pressure moving through the Great 
Lakes will spread rain, possibly mixed with snow in the north, and 
MVFR conditions into the forecast area Monday afternoon. The cold 
front will push across the district Monday night changing the rain 
to snow showers by early Tuesday morning. General MVFR ceilings 
can be expected late Monday into Tuesday with widespread Post 
frontal stratocu and scattered snow showers. Brief IFR/LIFR ceiling 
and visibility can be expected in snow showers. Widespread lake effect 
snow showers will persist into Wednesday into Thursday as cold 
upper low remains entrenched over New York state. 


&& 


Pbz watches/warnings/advisories... 
Maryland...none. 
Ohio...none. 
PA...none. 
WV...none. 


&& 


$$