Weather

804 
fxus61 kpbz 060223 
afdpbz 


Area forecast discussion 
National Weather Service Pittsburgh PA 
923 PM EST Monday Jan 5 2009 


Synopsis... 


A wintry mix of precipitation will spread across the region on 
Tuesday as low pressure advances from the south. The low is 
projected to cross the tri state area on Tuesday night and change 
precipitation to rain over many areas. The systems cold front will 
bring snow showers with colder air Wednesday. 


&& 


Near term /through Tuesday night/... 


Surface ridge will continue cold advection tonight ahead of low 
pressure moving northeast from the deep south. Wintry mix will 
develop across far southern zones before daybreak and spread north 
in the morning. Models have come into general agreement on colder 
solution as surface low remains farther south through much of 
Tuesday allowing colder air to maintain position. Advisories 
issued for mix generally from Pittsburgh south across County Warning Area. Warmer 
air will slowly push north to change precipitation to rain over 
southwestern zones of the County Warning Area by afternoon and 
over Pittsburgh by late day or early evening. Higher protected 
valleys in Preston and Tucker counties will hold onto cold air 
longer and kept advisory in place through Tuesday night. Advisory 
was also issued for counties to the north of pit for developing 
mix including freezing rain. As low projection has been slower to 
the north...easterly wind component may continue to reinforce 
colder air over those counties through the night. 


Cold air entrencment is also prognosticated to more widespread and 
prolonged over Garrett County. With amount of rain forecast, ice 
accumulation is excess of a quarter inch is anticipated...hence 
Winter Storm Warning has been issued for that zone with the evening 
update. 


&& 


Short term /Wednesday through Thursday/... 
systems cold front is still forecast to cross the upper Ohio on 
Wednesday and change precipitation to snow showers. Snow shower chances 
will continue on Thursday with area under northwest flow. 


&& 


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 /02z Tuesday through Saturday/... 


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


By daybreak 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. 


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 from 6 am Tuesday to 7 am EST Wednesday 
for mdz001. 
Ohio...Winter Weather Advisory from 7 am to 7 PM EST Tuesday for 
ohz039>041-049-050. 
Winter Weather Advisory from 4 am to 12 PM EST Tuesday for 
ohz048-057>059-068-069. 
PA...Winter Weather Advisory from 7 am to 7 PM EST Tuesday for 
paz020-021-029-030-032. 
Winter Weather Advisory from 1 PM Tuesday to 10 am EST 
Wednesday for paz007>009-013>016-022-023. 
Winter Weather Advisory from 4 am to 12 PM EST Tuesday for 
paz031. 
WV...Winter Weather Advisory from 7 am to 7 PM EST Tuesday for 
wvz001>003. 
Winter Weather Advisory from 4 am to 12 PM EST Tuesday for 
wvz004-012-021-022. 
Winter Weather Advisory from 4 am Tuesday to 7 am EST 
Wednesday for wvz023-041. 


&& 


$$ 


15/14