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Area forecast discussion 
National Weather Service Pittsburgh PA
639 PM EST Sat Jan 31 2015

Synopsis...
low pressure will bring wintry weather Sunday into Monday.

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Near term /until 6 am Sunday morning/...
updt to sky cover based on satellite and near term model data. With
clearing Erly lowered temperatures to the colder GFS numbers. Previous...high
pressure will continue to bring dry weather into the evening. A digging upper trough and
developing surface low pressure will begin to spread snow into the region lt tonight.
More on this in the short term section. Accumulations by morning
should be generally less than an inch as the precipitation will just be starting.

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Short term /6 am Sunday morning through Monday/...
that digging upper trough and surface low will continue to advance out of the
Midwest through our region Sunday Monday. Models have shifted the track of
the surface and closed 850 mb lows further north...shifting the focus for
heavier snow north of pit. A low level jet is prognosticated to develop along with deep
moisture and increasing Omega with warm advection later sun into Sun night...when
the heaviest precipitation is expd. Along with that warm advection...a
changeover to mainly rain is expd S of I 70...with a mix of
snow...sleet and freezing rain north to around pit. A brief changeover to all
rain is possible as well. North of I 80 should stay cold enough for all
snow. GFS was farthest north with the surface and 850 mb lows...and seemed
too aggressive with the warm advection. Opted for the colder NAM/European model (ecmwf)
solutions which allows for a little more gradual of a forecast shift. Relied
on critical thicknesses and model sounding profiles for precipitation type
forecast.

Issued a Winter Storm Warning for areas north of pit where 5 to 10
inches of snow are expd. From near pit and S to I 70 issued winter weather
advisories for 2-5 inches of snow and a potential for a wintry mix.
Watches are no longer in effect as areas S of the PA border...even
in the ridges...should change over to mainly rain. Freezing precipitation is possible
especially in Garrett County but held off on any addnl headlines at this time.

Wrap around snow behind the exiting low is expd Monday but only around an
inch or two of addnl snow is expd.

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Long term /Monday night through Saturday/...
only change to extended was to speed up frontal passage Wednesday
and bump up probability of precipitation. No other changes as much colder air pours in
behind the front as a Stout high pressure centers overhead.
Temperatures expected to be well below average from middle-week through
the end of the period.

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Aviation /00z Sunday through Thursday/...
VFR conditions will prevail through most of the night as the next
system start to increase high clouds across the area. Snow will
advance from SW to NE across all sites during the overnight and
predawn hours. Conditions will likely rapidly deteriorate to IFR
at most sites. The track of the system is continue to move
farther northwest on the latest forecast guidance such that the
middle-level dry slot is likely to go over almost all sites by
Saturday afternoon or evening. This should allow for warmer
surface air along with drier air aloft to make snow taper to light
rain or drizzle. Deeper mositure will return Sunday
night...bringing rain shwoers then snow showers back into the
forecast on Monday. Fries

Outlook.../Sunday night through Thursday/...
widespread restrictions can be expected into Monday as a low
pressure system crosses the region. Next chance for widespread
restrictions will be with a Wednesday cold front.

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Pbz watches/warnings/advisories...
Maryland...none.
Ohio...Winter Weather Advisory from 4 am Sunday to noon EST Monday
for ohz039-040-048>050-057>059.
Winter Storm Warning from 4 am Sunday to noon EST Monday for
ohz041.
PA...Winter Weather Advisory from 4 am Sunday to noon EST Monday
for paz021-029-073-074.
Winter Storm Warning from 4 am Sunday to noon EST Monday for
paz007>009-013>016-020-022-023.
WV...Winter Weather Advisory from 4 am Sunday to noon EST Monday
for wvz001>003.

&&

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