Area Forecast Discussion
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FXUS61 KPBZ 140844

Area Forecast Discussion
National Weather Service Pittsburgh PA
344 AM EST Sat Dec 14 2019

Rain is expected today with crossing low pressure. Rain will mix
with, and change to snow later today and tonight. Dry weather briefly
returns Sunday afternoon under building high pressure.


Rain and fog should continue across the area this morning with an
approaching shortwave trough and its associated sfc low. The low is
progged to track across Ern PA to New England this afternoon, with
backing wind and cold advection on the western side. Rain should mix
with and eventually change to snow later today in the cold advection,
though sfc and boundary layer temperatures should be warm enough to
preclude much accumulation outside of the higher terrain and areas
north of I 80.

Will mention 1-3 inches in the higher terrain, though there is a
potential for more if the rain transitions to snow faster in these
areas. Will include an Hazardous Weather Outlook mention for this. An
increasing pressure gradient this afternoon between low pressure to
our east, and high pressure to our west, should result in gusty W-NW
wind by this afternoon.


Rain and snow should change to all snow this evening as the boundary
layer cools. The snow should taper off later this evening and
overnight for most locations as the main trough axis shifts east.
Limited lake and terrain enhancement should maintain a few snow
showers overnight, though less than optimal westerly wind direction
and a lack of decent moisture in the dendritic layer should limit

Dry weather should return by Sunday afternoon under building high
pressure. The high should move east of the region Sunday night, as a
digging Central CONUS trough moves east. A developing sfc low in
response to the approaching trough, should track from the MS Valley
to the OH Valley region late Sunday night and Monday, returning
precip to the forecast. Model soundings and critical thicknesses
indicate snow is likely initially Sunday night and Monday morning,
with a transition to mainly rain from S-N.

There could be a brief wintry mix during the transition. At this
time, it appears an inch or two of snow will be possible for some
areas before the transition. Some locally heavy rainfall is also
possible, but placement is in question with uncertainty in the exact
track of the low.


The Central CONUS trough should maintain precipitation chances
through early Wednesday as it crosses. Mainly dry weather is then
expected through the end of the week under a building ridge. Colder
than average temperatures should return to seasonable levels by


IFR in rain is expected to become widespread through much of the day
as a shortwave trough and associated low pressure track across the
area. The low is progged to be across NY this afternoon, with backing
wind and cold advection on the wrn side. Rain should mix with and
eventually change to snow this aftn/eve, with continued IFR. The
upper trough axis should shift east tonight, with scattered snow
showers and some improvement to low end MVFR.

A tightening pressure gradient on the wrn side of the low should
result in gusty W-NW wind this afternoon and evening.

Restrictions are likely again on Monday and Tuesday with the crossing
of another low pressure system.




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