Prognostic Meteorological Discussion
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FXUS01 KWBC 220803

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
302 AM EST Thu Feb 22 2018

Valid 12Z Thu Feb 22 2018 - 12Z Sat Feb 24 2018

...Cold and unsettled weather is expected over the West including
some heavy snow over the Rockies...

...Additional heavy rainfall and widespread concerns for flooding
will persist across parts of the southern Plains, lower
Mississippi Valley and the Ohio Valley...

...Warm temperatures are generally expected to continue across a
large portion of the East...

Much of the West will remain in a cold, active wet pattern through
the end of the week thanks to a series of impulses that will drop
south and reinforce the broad upper level trough of low pressure.
Snow will spread across the Pacific Northwest, Great Basin and to
the Rockies. Snow will be heavy at times across the higher terrain
in northern California, southern Idaho, Nevada, Utah and for
portions of the Central Rockies. The cold airmass in place over
the region will keep afternoon highs generally 10 to 20 degrees
cooler than usual for late February.

The waves of energy will exit the Front Range and track across the
Plains where a quasi-stationary frontal boundary extends from the
Lower Mississippi Valley to the Ohio/Tennessee Valley and
Mid-Atlantic. Multiple rounds of heavy rain is forecast as warm
Gulf moisture advects northward along the boundary. This rainfall
is expected to occur over a broad area already saturated from
prior days of excessive rain. A slight to moderate risk for flash
flooding main stem river flooding will persist through the end of
the week. In the cold sector, scattered to widespread snow will be
possible for portions of the Plains, Midwest and Upper Mississippi
Valley - numerous Winter Weather Advisories are in effect for
these areas.

Much of the East Coast lies within the warm sector of this system
and will continue to have temperatures topping off in the 70s and
80s, whereas, the central CONUS will be below freezing as much as
10 to 20 degrees below normal.

Regarding the threat of winter weather, there will be the approach
of a wave of low pressure from the Tennessee Valley on Thursday
that will actually interact with sufficient cold air over parts of
the upper Ohio Valley, far northern Mid-Atlantic and interior of
the Northeast for a stripe of some accumulating snow and ice.
Meanwhile, there will also be a swath of accumulating snow and ice
across portions of especially the central Plains, Midwest and
Great Lakes for Thursday and Friday as low pressure rides
northeast up across the region.


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