ACUS02 KWNS 180602
SWODY2
SPC AC 180600

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Tue Aug 18 2020

Valid 191200Z - 201200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
NORTHERN INTERMOUNTAIN REGION...SOUTHWARD ACROSS THE HIGH
PLAINS...AND WESTWARD INTO THE DESERT SOUTHWEST...

...SUMMARY...
Isolated strong/locally severe storms will be possible within a
large, arc-shaped area from portions of Idaho and southwestern
Montana eastward into parts of South Dakota and Nebraska, southward
across the central and southern High Plains, and westward to
southeastern Arizona.

...Synopsis...
Gradual deamplification of the upper flow field is expected
Wednesday, though the general western ridge/eastern trough
configuration is expected to remain, with numerous small, cyclonic
disturbances moving through the flow field.

At the surface, a baroclinic zone will linger from the Carolinas
across the Gulf Coast states, with high pressure prevailing behind
this front over much of the rest of the eastern half of the country.
In the West, lee troughing will persist over the High Plains.

...Northern Intermountain region, High Plains, and into the Desert
Southwest...
As has been the case for the past several days, multiple small-
scale disturbances embedded within the enhanced anticyclonic flow
field around the western U.S. ridge will contribute to areas of
afternoon and evening convective development.  Narrowing down areas
of potentially greater risk remains quite difficult -- particularly
given limited instability across most of the region.  While slightly
greater risk may evolve across the eastern Oregon/Idaho/western
Montana vicinity, no upgrade to SLGT risk/15% probability will be
included at this time, due to lingering concerns about degree of
severe-weather coverage.  Elsewhere, isolated/stronger
storms/clusters will be capable of producing strong wind gusts --
aided by the dry sub-cloud layer expected to reside across the
region.

...The Southeast north to the Chesapeake Bay area...
Diurnal heating/destabilization across the southeastern quarter of
the country -- near and southeast of a weak east-northeast to
west-southwest baroclinic zone -- will result in scattered to
numerous thunderstorms developing during the afternoon.  While
storms are expected to remain largely sub-severe, owing to generally
modest mid-level lapse rates and weak low-level flow, moderate
mid-level west-southwesterlies may permit a few multicell clusters
to evolve, with possible/associated risk for locally strong gusts
capable of producing some tree damage.  However, with threat
expected to remain limited, and over a very broad area, no risk area
will be highlighted at this time.

..Goss.. 08/18/2020

$$