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000 
FXUS61 KPBZ 131451
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
951 AM EST Fri Dec 13 2019

.SYNOPSIS...
Precipitation chances return today with a weak disturbance. 
Widespread rain is expected tonight and Saturday with crossing low 
pressure.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

Late Morning Update: Due to lingering freezing conditions, the
Winter Weather Advisory was expanded further north and west. Icy 
conditions have been reported in Marion, Preston, and Garrett County.
Warm advection should increase temps to above freezing west of the 
ridges in the next few hours. Eastern Tucker/Garrett's Advisory may 
need to be extended if temperatures can not make it above freezing 
due to dynamic cooling.

Previous Discussion: 

Quick update to expand the advisory to Preston and Wrn Tucker 
counties this morning. Precip advancing NEWD on radar, with 
temperatures in those areas mainly in the 20s. Expect some warming 
before precip arrives, though some areas are still expected to be 
below freezing. Previous...A shortwave embedded in SW flow aloft is 
progged to track from the Tennessee Valley to Central/Eastern PA 
today. Mainly slight/low chances for rain are expected across the 
region, though the higher terrain areas across Wrn MD and Nrn WV are 
expected to be closer to more favorable upper support and deep layer 
moisture with precip more likely. 

With cold air in place at the sfc, and cooling upslope SE
flow, a period of light freezing rain is expected across Ern Tucker
and Garrett counties. Will maintain the Winter Weather Advisory as
is. Some brief, patchy, light freezing rain is possible across
Preston county through the Laurel Highlands if precip occurs this
morning. If later information indicates higher precip probabilities
in these areas, a quick expansion of the advisory may be needed,
otherwise not enough confidence in this occurrence to expand the
advisory attm. 

Expect any precip to taper off this afternoon with the passage of the
initial wave, with seasonable high temperatures.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
An upper trough is progged to dig across the Central CONUS tonight,
crossing the Upper OH Valley region Saturday. A sfc low is expected
to develop across the SE CONUS in response to the digging upper 
trough, tracking along the East Coast over the weekend. Rain should
overspread the region tonight and Saturday in warm, moist advection 
and increasing shortwave support. QPF amounts are expected to range
from 1/3 to 3/4 of an inch, so no significant hydro concerns are 
anticipated. 

Rain should mix with and eventually change to snow in cold advection
after the sfc low tracks by to our E/NE later Saturday and Saturday
night, though no significant accumulation is expected with the 
sfc/boundary layer slowly cooling for most locations, though colder
areas across the higher terrain could see a couple of inches. 

Snow shower chances should continue Sunday both with upslope flow,
and a sfc trough across Lake Erie/NW PA. Moisture in the dendritic
layer is expected to be limited, precluding any more than a coating
of additional accumulation in some areas. Brief shortwave ridging
should return dry weather most of Sunday night, though snow chances
return late with another approaching Central CONUS trough and
associated sfc low.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Rain and snow chances increase Monday and Tuesday as the trough and
sfc low track across the region. A reinforcing trough should maintain
low/slight snow shower chances Wed before low level ridging returns
mainly dry weather Thursday. Temperatures should average below
seasonable levels through the period.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
MVFR cig restrictions expected today with increasing moisture and a
crossing shortwave. Any precipitation will be scattered and light
during the day. Further deterioration to IFR or lower is expected
tonight through Saturday with more widespread precipitation
associated with low pressure moving up the coast. Nearly all analogs
show IFR restrictions during this time and 60-80% indicate LIFR
restrictions.

.Outlook... 
Restrictions are likely through much of the weekend.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...Winter Weather Advisory until 3 PM EST this afternoon for MDZ001.
OH...None.
PA...Winter Weather Advisory until 11 AM EST this morning for PAZ031-
     074>076.
WV...Winter Weather Advisory until 11 AM EST this morning for WVZ021-
     509>513.

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