926 
fxus61 kctp 220058 
afdctp 


Area forecast discussion 
National Weather Service State College PA 
758 PM EST Sat Nov 21 2009 


Synopsis... 


An anomalous strong upper ridge will dominate our weather through 
mid-week. Then a series of waves will carve out a trough over 
eastern North America beginning about Thanksgiving. The strong 
trough which develops by the weekend and the ridge over western 
North America. It will turn colder around Thanksgiving. 


&& 


Near term /until 6 am Sunday morning/... 


Updated the grids and will push out a new zone set based on these 
edits as the low clouds are eroding fast. 3.9-11 micron data shows 
potential clearing as far north as State College now. Still lots 
of low clouds across the north and west. 


Profiles show the inversion near 750-780 hpa weakening a bit and 
considerable drying below this feature. This would favor the 
improved weather and less clouds over State College and points 
south and east. However the Bradford profile suggests it will take 
a good 6 to 8 hours to dry out up there. 


Additionally...there is some potential for valley fog as the T-dew point 
spread is small. A good period of radiation would help produce 
some fog. Kept patchy fog in forecast. 


Overnight lows will mainly be upper 30 and lower 40s. Dew points 
are mainly in the upper 30s and lower 40s. 


&& 


Short term /6 am Sunday morning through Sunday night/... 
morning patchy fog will dissipate by middle to late morning...and 
with continued ridging surface and aloft...expect skies to become 
partly to mostly sunny everywhere with a milder afternoon. 
Naefs gives higher mav MOS temperatures...ranging in the l/m50s most 
spots. 


Expect increasing low level moisture from deep east/southeast flow 
Sunday night as surface ridge tracks towards Newfoundland bringing a 
large over water fetch into the Middle Atlantic States. At the same 
time...a decaying upper wave impinging upon the upper ridge from 
the west over the Ohio Valley will spread deeper layer moisture 
across the region by late Monday. The result will be a slight 
chance of light rain by dawn Monday...with much better chances 
later Monday as the cad is well established below warm air advection aloft. 


&& 


Long term /Monday through Saturday/... 
models have weak system lifting NE from the Gulf area later on 
Monday into Tuesday. Did slow things down some and think bulk of 
any rain would hold off to after. Did cut probability of precipitation back some. Expect 
amts to be on the light side. 


Some clouds and light rain...drizzle for the most part...could 
linger into Tuesday. 


Quite a bit of variation in model solutions. Could see northern 
and western areas staying dry. 


For Wednesday...central PA is between systems. GFS looks fast... 
HPC not as fast... weighted forecast to slower speed. 


Overall...only made a few minor changes to the package. 


For Thursday into Sat...temperatures cooling off closer to normal...as 
ridge builds across the western states...and more of a trough 
pattern prevails across the eastern states. Some rain and 
snow showers will be possible across the mts Thursday into Friday. 


Enough ridging may take place on Saturday...to keep most of the 
area dry. 


&& 


Aviation /01z Sunday through Thursday/... 
infrared imagery indicating considerable stratus holding onto the atmos 
over PA...expect for the susq-valley where it remains few/skc. 
Guidance suggests as flow turns north/NE boundary layer will dry and erode 
stratus deck between 09-12z. A few locations could see patchy fog 
dev...however expect this to be local. Elsewhere anticipate skies to 
bounce to VFR conds and persist through 00z Monday. 


Outlook... 
Monday...MVFR local IFR. Possible rain showers in the afternoon. 
Tuesday...MVFR/IFR ceilings. Rain showers in the am. 
Wednesday...MVFR to VFR. 
Thursday...MVFR with chance -shrasn. 


&& 


Ctp watches/warnings/advisories... 
none. 


&& 


$$ 
Synopsis...grumm 
near term...grumm 
short term...devoir 
long term...Martin 
aviation...beachler