SPC Aug 17, 2020 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0236 AM CDT Mon Aug 17 2020

Valid 191200Z - 201200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN INTERMOUNTAIN REGION...AND SOUTHWARD ACROSS THE HIGH
PLAINS...

...SUMMARY...
Isolated strong/locally severe storms will be possible from portions
of Idaho and southwestern Montana eastward into parts of South
Dakota and Nebraska, and southward across the central and southern
High Plains.

...Synopsis...
Deamplification of the upper flow field is expected across the U.S.
Wednesday, as suppression of the western upper ridge continues. 
Within the anticyclonic belt of enhanced mid-level flow around the
ridge, several embedded vorticity maxima will help support a large
area of western U.S. to High Plains convective potential.  Farther
east, scattered -- though primarily sub-severe -- thunderstorms are
expected generally east of the Mississippi River and south of the
Ohio River, and northeastward into New England.

At the surface, high pressure will prevail over much of the East,
though a weak baroclinic zone will linger from the Carolinas across
the Gulf Coast states to Texas.  Meanwhile, lee troughing will
persist over the High Plains.

...Northern Intermountain region to the central and southern High
Plains...
Isolated afternoon thunderstorms are expected to evolve across a
large portion of the western U.S., as modest CAPE and differential
heating over higher terrain combine to support convective
development.  Development will likely be augmented as a series of
cyclonic disturbances move through the fast anticyclonic flow field
aloft.  At this time, narrowing down these areas of greater storm
potential remains difficult, hence a broad MRGL/5% risk area --
primarily for afternoon and evening wind gust potential with
stronger storms.

An eastward extension of the risk area -- into parts of South Dakota
and Nebraska -- is being included, where increased warm advection
may evolve after dark in conjunction with a developing/southerly
low-level jet, as hints that a more prominent upper disturbance may
shift across the northern High Plains during the evening, supporting
potential for an eastward convective expansion.

..Goss.. 08/17/2020

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from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day3otlk_0730.html