110 
fxus61 kpbz 210726 
afdpbz 


Area forecast discussion 
National Weather Service Pittsburgh PA 
226 am EST Friday Nov 21 2008 


Synopsis... 


A cold northwest flow will bring lake effect snow showers to the 
region through tonight. Lingering snow showers will persist north 
on Saturday...as high pressure begins to build in from the southwest. 


&& 


Near term /through today/... 


Have primarily seen two dominant lake effect bands overnight. Expect the 
more dominant banding to continue this morning...with a more widespread 
area of bands developing for the afternoon...as the thermal 
trough drops south. With the chance for any persistent bands to 
produce significant snow amounts in a short period of time...will 
leave warnings and advisories where they are. 


&& 


Short term /tonight through Sunday/... 


The flow will begin to turn more toward the west/northwest 
overnight...with the thermal trough moving east. This will limit 
most of the accumulating snows tonight and early Saturday to the 
northern tier of counties. High pressure will build northeast 
Saturday afternoon bringing an end to accumulating snows. This 
high will provide for dry conditions with some sunshine for 
Sunday. 


&& 


Long term /Sunday night through Thursday/... 
recent blend of gefs and European model (ecmwf) model runs show that at the upper 
levels Sunday night through Wednesday the cold pattern continues 
with ridge in the western portion of the USA and a trough in the 
east. Temperatures remain below normal. On Thursday western ridge 
breaks down somewhat and we nearly go zonal. Therefore temperatures on 
Thursday near normal. The next potential for precipitation is 
Monday and Tuesday as a cold front approaches from the northwest. 
Tuesday night and on into Wednesday morning still a chance for 
snow showers in northwest flow. Wednesday during the day and 
Thursday high pressure builds in from the west. 


&& 


Aviation /07z Friday through Tuesday/... 


Cold northwest flow off of the warmer waters of lakes Erie and Huron 
will bring bands of lake effect snow showers across the forecast 
area today. The heaviest bands will be in northwest PA with the fkl 
and duj airports most impacted. Outside of the snow bands an MVFR ceiling 
of stratocu can be expected with VFR visibility. Within the snow showers 
of the snow bands IFR conditions can be expected along with 
occasional LIFR ceilings and visibility in the heavier snow showers. Northwest 
surface winds of 10 to 15 knots today with gusts to 25 knots. Chilly 
northwest flow continues tonight with a continued risk of lake 
effect snow showers but snow showers will weaken in intensity and 
coverage as northwest flow weakens. 


High pressure will build into our area for Saturday and 
Sunday...with mainly VFR conds expected. Next chance for lower 
flight conditions will come with the approach and passage of a cold 
front Monday. Cold northwest flow can expected Tuesday with a return 
to lake effect snow showers. 


&& 


Pbz watches/warnings/advisories... 
Maryland...Winter Storm Warning until 6 PM EST this afternoon for mdz001. 
Ohio...Winter Weather Advisory until 6 PM EST this afternoon for 
ohz041. 
PA...Winter Weather Advisory until 6 PM EST this afternoon for 
paz013>016-020>023. 
Winter Storm Warning until 6 PM EST this afternoon for paz030- 
032. 
Lake effect snow warning until 6 PM EST this afternoon for 
paz007>009. 
WV...Winter Storm Warning until 6 PM EST this afternoon for wvz023- 
041. 


&& 


$$ 
Ls