Prognostic Meteorological Discussion
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592
FXUS01 KWBC 221953
PMDSPD

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
353 PM EDT Sun Apr 22 2018

Valid 00Z Mon Apr 23 2018 - 00Z Wed Apr 25 2018

...Thunderstorms and heavy rain with possible flash flooding for
the southern Appalachians and Southeast for the early part of this
week...

...Accumulating snow expected over parts of the northern Rockies
and northern High Plains beginning tonight...

An upper level low, currently approaching the lower to middle
Mississippi valley, will keep locations from the Ohio valley to
the Mid-Atlantic and Southeast unsettled over the next couple of
days. The greatest threat from this storm system will be heavy
rain, with a broad 1 to 3 inches expected through Tuesday evening
from the Tennessee valley into the southern Mid-Atlantic region.
Higher rainfall totals of 3 to 6 inches are expected for portions
of the southern Appalachians where flood watches have been issued
through Tuesday morning. Locally heavy rainfall with this storm
system could bring flash flooding to a broad section the Southeast
and Mid-Atlantic through Tuesday night.

Moisture from the Gulf of Mexico and western Atlantic will
converge upon the Southeast late tonight into Monday with
moderately strong southeasterly winds ahead of the upper low
allowing for upslope enhancement to precipitation totals. Gusty
winds will also be a factor across the Southeast, especially into
the mountainous terrain tonight through Monday, with gusts
possibly peaking in the 50-60 mph on Monday. A high wind warning
is in effect for portions of the southern Appalachians through
Monday night with downed trees and power lines a possibility as a
result of the strong winds.

The other significant weather system to impact the lower 48
through the early week will reach the northern Rockies tonight.
Rain and higher elevation snow will develop tonight across Idaho
into Montana and Wyoming near a frontal boundary and upper level
disturbance. As the system moves east early Monday, colder air
will filter in allowing a changeover from rain to snow for many
lower elevation locations. The heaviest snowfall accumulations,
4-8+ inches, will be focused across the higher terrain of the
Absaroka and Big Horn Mountains, but light to locally moderate
snowfall accumulations are also expected eastward along the
Montana/Wyoming border into the High Plains and Black Hills. Cool
and rainy conditions will reach parts of the central and northern
Plains on Tuesday. High pressure associated with colder
temperatures will also filter in behind the storm system`s cold
front, bringing high temperatures into the 10-20 degree below
average range for Montana/Wyoming on Monday and into the central
Plains for Tuesday.

Otto


Graphics available at
www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
$$





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