Weather

878 
fxus61 kpbz 060841 
afdpbz 


Area forecast discussion 
National Weather Service Pittsburgh PA 
341 am EST Tuesday Jan 6 2009 


Synopsis... 


A wintry mix will overspread the region today as a low pressure 
system moves northeast through the Ohio Valley. This will continue 
to affect the region into Thursday. 


&& 


Near term /until 6 PM this evening/... 


Complex weather scenario today...as low moves north through Ohio 
Valley. Cold air is in place at the surface...with warmer air 
surging in aloft. This will lead to a wintry mix. A gradual 
transition to primarily rain will take place later today...as the 
warmer air works north. However...the cold air will be hard to displace in 
more sheltered valleys...and especially hard east of the ridges. 
As a result a significant accumulation of ice will be possible in 
Garrett County...with lighter icing amounts elsewhere. 


&& 


Short term /6 PM this evening through Thursday/... 


Mainly rain is expected tonight. As colder air filters in 
through the column Wednesday...a mix of rain/snow is expected. 
The chance for snow will continue right into Thursday...behind the 
exiting low. 


&& 


Long term /Thursday night through Monday/... 
below normal temperatures through the period in northwest flow. 
Chance of snow ending Thursday night as ridge of high pressure moves 
in from the west. Dry on Friday under ridge of high pressure 
centered over southeast USA. Snow showers redevelop Friday night and 
continue through Sunday with the approach and passage of a cold 
front. Mostly cloudy and continued cold on Monday in weakening 
northwest flow. 


&& 


Aviation /09z Tuesday through Saturday/... 


Expect VFR flight conditions to continue into the morning hours as 
overcast middle deck streams eastward along the Ohio Valley ahead of 
approaching low pressure system. 


By middle morning Tuesday...conditions will begin to deteriorate south 
of kzzv to kmgw line. Generally MVFR/scattered IFR conditions are 
forecast as precipitation begins...with IFR prevailing later in the 
day Tuesday. Initial precipitation type will be snow...with gradual 
changeover to ice pellets and then freezing rain by late in the day 
Tuesday and Tuesday night as cold air at lower levels erodes. 


A cold frontal passage Wednesday will change rain to snow showers 
by late afternoo. Behind the front a strong push of Arctic air will 
begin Wednesday night. This will be the beginning of a colder/snowy 
pattern which will continue into the weekend. MVFR/IFR restrictions 
are likely. 




&& 


Pbz watches/warnings/advisories... 
Maryland...Winter Storm Warning until 7 am EST Wednesday for mdz001. 
Ohio...Winter Weather Advisory from 8 am this morning to 7 PM EST 
this evening for ohz039>041-049-050. 
Winter Weather Advisory until 1 PM EST this afternoon for 
ohz048-057>059-068-069. 
PA...Winter Weather Advisory from 8 am this morning to 7 PM EST 
this evening for paz020-021-029-030-032. 
Winter Weather Advisory from 1 PM this afternoon to 10 am EST 
Wednesday for paz007>009-013>016-022-023. 
Winter Weather Advisory until 1 PM EST this afternoon for 
paz031. 
WV...Winter Weather Advisory from 8 am this morning to 7 PM EST 
this evening for wvz001>003. 
Winter Weather Advisory until 1 PM EST this afternoon for 
wvz004-012-021-022. 
Winter Weather Advisory until 7 am EST Wednesday for wvz023- 
041. 


&& 


$$