556 
fxus61 kctp 100735 
afdctp 


Area forecast discussion 
National Weather Service State College PA 
235 am EST Wednesday Mar 10 2010 


Synopsis... 
high pressure will slide northeastward to the New England states by 
Wednesday afternoon. A large upper storm will move slowly eastward 
from the plains late this week...accompanied by several waves of 
low pressure advancing northeast just ahead of it. Clouds will 
increase late Wednesday and Thursday before abundant moisture 
surges northward...producing several periods of significant 
rainfall late Thursday through Saturday. Cooler air will filter 
into the region later this weekend...allowing wet snow to mix in 
at times across the mountains. 


&& 


Near term /until 7 am this morning/... 
upper level ridge axis over the Ohio Valley beginning to be 
overrun by high level moisture. GOES infrared and visible imagery indicate 
thin high clouds streaming over central PA. This will continue to 
be the case for the overnight as the midwestern upper low begins 
to decay in favor of the vigorous system currently tracking into 
The Four Corners region. No precipitation is expected as the llvls remain 
very dry and moisture aloft is thinning as it moves through c Ohio. 


Temperatures to fall to the coolest readings in the north where clouds stay 
away longest...and previous days temperatures were lower than rest of c PA. 
Kept temperatures lower than all guidance with previous days MOS running too warm 
at night...but did not stray far with high clouds overhead. 


&& 


Short term /7 am this morning through 6 PM Thursday/... 
the backdoor cold front across our NE zones...and warm front 
advancing gradually NE up the Ohio River valley...will create a 
squeeze play across the region Wednesday...with layer clouds 
thickening up through the day. Little if any precipitation is 
expected but if it occurs would be in the vicinity of the warm 
front over the high terrain of The Laurels and western mountains. 


Less sunshine than Tuesday will most likely limit the number of 60+f 
observation seen around the region in the afternoon...but MOS has been running 
very cold vs reality lately on maxes...so will go 3-5f above MOS 
in most locations...especially the hot spots in the susq valley like ipt/seg 
and MDT. 


&& 


Long term /Thursday night through Tuesday/... 
not a lot of change from recent days. I did up maximum temperatures some... 
mainly across the susq valley on Thursday into Friday...given lack of 
snow cover...warm advection...and really not looking at much 
rain before late Friday night...especially on Thursday. 


GFS hinted yesterday that a secondary low would develop this 
weekend...and cutoff. This low would remain across the area 
into early next week. 


The GFS rotates new low to the west...this may be a little 
overdone. Also the European model (ecmwf) moves this system out faster next 
week...think I prefer this...as I think the upper level 
ridge will expand eastward into the lower lakes area. 


The main concern is rainfall. Think there is potential for 
1 to 2 inches of rain...mainly from 12z Sat into early Sunday 
morning...mainly across the susq valley eastward...given strong 
southeast flow...warm advection...dynamics...and thermal ridge. 


A small amount of wet snow may mix with the rain Sunday night... 
and Monday night across the northwest. 


GFS would support another East Coast storm by the following 
weekend. Time will tell. Anyway...enjoy the nice weather. 


&& 


Aviation /06z Wednesday through Sunday/... 
VFR conditions will continue through next 24 hours as just high 
clouds sliding in overhead tonight followed by gradually lowering 
middle deck later today...with ceilings likely lowering to around 5kft by 
11/00z. Surface winds will continue to be light through the period. 


Cannot rule out scattered showers later Wednesday into Thursday as warm front 
lifts northeastward through the Ohio Valley. Expect an increase in coverage and 
intensity of rainfall this weekend as conditions deteriorate to 
MVFR/IFR. 


Outlook... 
Wednesday...VFR becoming MVFR ceilings Wednesday night. Isolated-scattered light rain showers possible afternoon. 
Thursday...MVFR ceilings becoming widespread IFR in light-moderate rain. Low level wind shear possible. 
Fri-sun...MVFR/IFR continue in periods of rain...heavy at times. 


&& 


Ctp watches/warnings/advisories... 
none. 


&& 


$$ 
Synopsis...devoir 
near term...dangelo 
short term...dangelo/devoir/Lambert 
long term...Martin 
aviation...rxr