Area Forecast Discussion
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FXUS61 KPBZ 160440

Area Forecast Discussion
National Weather Service Pittsburgh PA
1140 PM EST Sun Dec 15 2019

A wintry mix of precipitation is expected tonight through Tuesday
with crossing low pressure.


Adjusted timing of POPs and snow accumulation based on latest radar,
sfc obs, and snow reports.

Previous...Regional radar suggests a band of snow has developed in
association with an encroaching, lead shortwave. Lingering low-level
dry air evident in the evening sounding out of PIT should quickly
saturate with strong jet dynamics aloft, and snow should overspread
the region from south to north as the night progresses.

The overrunning of warm air aloft on the van of a broad, upper trough should
support a changeover from snow to a wintry mix of sleet and freezing
rain along and just north of the I-70 corridor.

An accumulation of a couple inches of snow followed by a glaze of
ice can be expected for southern portions of the forecast area under
the Winter Weather Advisory headline where better forcing for ascent
exists. Higher ice accumulation amounts are anticipated in Garrett
County, MD as surface southeasterly wind supports dynamic cooling.
This, combined with strong warm advection aloft will lead to a
prolonged period for freezing rain. As such, a Winter Storm Warning
remains valid.

For locations outside of the current winter headlines, including the
Pittsburgh metro, high resolution models suggest cold enough
temperature to support mostly snow through daybreak with general
accumulations around an inch expected.


Snow will continue in our southern counties early Monday morning
with the passing shortwave. A period of freezing rain from 7am to
10am , roughly along and south of I-70, may occur due to moist warm
advection. Additional counties may need to be added to the Winter
Weather Advisory late tonight if confidence for winter hazardous

With building mid-level subsidence south of the Great Lakes,
precipitation will cease by the late morning north of Pittsburgh.
However, additional shortwave support and moist advection should
increase precip coverage later in the day Monday and Monday night.
Much of the area should see rain through locations N of PIT could
also see a wintry mix as temps aloft warm, but the sfc temps remain
cold. Precip should become light and change to mainly snow Tuesday in
cold advection behind the exiting sfc low.


Snow shower chances continue Wednesday with cold NW flow and a
crossing upper trough. Generally dry weather is then expected through
the Friday under a building ridge ahead of a wrn CONUS trough.
Slight chances for precip return Saturday as the trough approaches.


Approaching low pressure is poised to spread snow over the region
as the night progresses. Expect deterioration to IFR in the predawn
of Monday with snow transitioning to a wintry mix from the south as
the early-morning progresses. A break in IFR and precip is expected
by midday, but redeterioration is anticipated later in the day as the
main trough axis encroaches.

Restrictions are likely through Tuesday with crossing low pressure.


MD...Winter Storm Warning until 7 PM EST Monday for MDZ001.
OH...Winter Weather Advisory until 10 AM EST Monday for OHZ057>059-068-
PA...Winter Weather Advisory until 10 AM EST Monday for PAZ031-075-076.
WV...Winter Weather Advisory until 10 AM EST Monday for WVZ003-004-012-


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