439 
fxus61 kctp 220947 
afdctp 


Area forecast discussion 
National Weather Service State College PA 
432 am EST Sat Nov 22 2008 


Synopsis... 
a deep upper level trough will dominate our weather through 
today...keeping central Pennsylvania unseasonably cold with lake 
effect and orographically enhanced snow showers. Localized heavy 
snow squalls could produce brief whiteout conditions. High 
pressure will build over the region tonight and Sunday. The next 
storm is slated for the Monday-Tuesday time frame. Post storm 
northwesterly flow should re-generate lake effect for the rest of 
next week. 


&& 


Near term /through tonight/... 
deep cold air traversing the relatively warm waters of the Great 
Lakes will continue to produce periods of orographic snows/squalls 
through today across the Allegheny plateau...with a few embedded 
bands of heavy snow squalls. More persistent lake effect snows will 
impact Warren and western McKean counties. 


Some interesting features (i.E., Narrow snow squall bands) are 
inferred by the 13km RUC and the wrfarw as far southeast as the central 
mountains at times today...into tonight. The main axis of boundary layer 
(sfc-1000m) Theta-E convergence and quantitative precipitation forecast stretches on a 300-310 degree 
axis from near Keri to kfig and kunv this afternoon and 
evening...before backing about 10-20 degree shifting the band NE 
between kunv and kipt later tonight. 


Moderately strong uvvel and deep moisture coincide near...or just 
under the primary dendritic snow growth thermal ribbon of -13 to 
-18. The 06z NAM actually indicates the best focus for the squalls 
near kunv from 00z to 05z Sunday. 


Subsidence inversion quickly drops to below 3 kft above ground level before 12z 
Sunday with any weak Omega falling well below the main dendritic 
snow growth region. 


Will maintain the previous lake effect snow warnings and winter 
weather advisories across the northwest mountains through 23z today...and even 
expand the advisories to cover northern Centre County and the 
likely...more persistent bands of heavier snow showers/squalls. 


The central valleys...near kunv will likely see an additional 1-2 
inches of wind whipped snow today with highly localized 3-4 inch 
totals possible by midnight. 


Maximum temperatures today...ranging from the l20s in the mw to the middle 30s 
in the lower susq valley will be about 15f below normal. Adding to 
this will be the gusty west to northwest which will make it feel 
like the single digits for much of the day over the mountains...and in 
the teens elsewhere. 


&& 


Short term /Sunday/... 
as winds lighten up tonight and skies go partly cloudy in many 
areas southeast of the Allegheny Front...this will set US up for perhaps 
the coldest night over all the area so far this winter with the 
fresh snow pack. 


Lows early Sunday will range from 10 to 15f across the mountains...and 
15 to 20 degrees elsewhere. Some locations across the north 
central mountains...where breaks in the waning strato cumulus deck should be 
most numerous...will see the Mercury dive into the single digits. 
&& 


Long term /Sunday night through Friday/... 
cold weather pattern to continue through the extended...with a 
possible yet gradual warming trend for the second half of 
Thanksgiving weekend. 


Temperatures will moderate a bit Sunday into Monday ahead of the next 
cold front...but will still remain below normal. Precipitation moves in 
from the west Monday...reaching eastern sections by afternoon. 
Atmosphere may be warm enough ahead of front to support rain mixed 
with snow for several hours. 


System stalls to the east as upper trough again deepens. North/northwest flow 
will bring lake effect clouds and snow showers to mainly the 
western counties Monday night into Wednesday. As cyclonic flow 
continues...low pressure will intensify somewhere near the coast. 
There still remains some uncertainty of just how this low will 
play out...but regardless unsettled weather will start the 
Thanksgiving weekend. Trough lifts to the NE late in the period 
with improvement in store for the weekend. 


&& 


Aviation /10z Saturday through Wednesday/... 
multiple lake effect snow bands will continue to affect 
west/central PA airfields today...before slowly diminishing 
overnight. Terminal forecasts remain redundant...with the worst 
flying conds xpected over the high elevation sites bfd/jst. 
Aoo/unv will fluctuate between MVFR/VFR with mainly VFR prevailing 
in the east. 


West-northwesterly surface winds 8-12kts will increase this afternoon to 12-15kts with 
20-25kt gusts before diminishing after dark. 


The low level flow will back more to the west southwest on 
Sunday...effectively shutting down the lake effect snows across western 
PA. VFR flying is xpected to last into Sun night/early Monday. 


The next storm system will arrive Monday afternoon/evening accompanied by 
rain/snow. This system is forecast to intensify as it moves NE into New 
England Tue/Wed...with periods of snow continuing into middle week. 
Look for MVFR and IFR conds in the west/central. 


&& 


Ctp watches/warnings/advisories... 
lake effect snow warning until 6 PM EST this afternoon for 
paz004-005. 
Winter Weather Advisory until 6 PM EST this afternoon for 
paz006-010-011-017-018. 


&& 


$$ 
Synopsis...Lambert 
near term...Lambert 
short term...Fitzgerald/Lambert 
long term...beachler/rxr 
aviation...Martin/steinbugl