SPC 0100Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0751 PM CDT Wed Sep 23 2020

Valid 240100Z - 241200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ISOLATED STRONG
STORMS MAY POSE SOME RISK FOR SEVERE WEATHER TONIGHT ACROSS PARTS OF
CENTRAL AND SOUTHERN MISSISSIPPI...PORTIONS OF THE UPPER
MIDWEST...AND WEST OF THE WASHINGTON CASCADES...

...SUMMARY...
Thunderstorm activity which could pose at least some risk for a
tornado may persist tonight across parts of central and southern
Mississippi.

...01Z Outlook Update...

...Lower Mississippi Valley...
Thunderstorm activity has generally been confined to a short narrow
band, just in advance of the center of Beta, apparently aided by a
weak mid-level thermal trough (as suggested by the Rapid Refresh
near/just above 700 mb).  As the surface low center of Beta migrates
across the Mississippi River into southwest/west central Mississippi
overnight, it is possible that this may continue.  Supported by
inflow of boundary-layer moisture characterized by lower/mid 70s F
dew points, in the presence of modest clockwise curved low-level
hodographs, it is possible that there could be occasional low-level
mesocyclone strengthening which could pose at least some risk for a
tornado.


...Elsewhere...

...Thunderstorm activity may continue to increase this evening, into
the overnight hours, within a narrow corridor along a frontal zone
across parts of north central Minnesota into northern Wisconsin and
adjacent Upper Michigan.  This may be aided by forcing associated
with a short wave trough digging into the region, and its possible
that thermodynamic profiles and cloud-bearing layer shear may be
marginally conducive from some hail and gusty winds in stronger
storms.

...Isolated thunderstorm development has also occur ahead of the
digging mid-level trough across parts of the western Dakotas, where
boundary-layer instability largely driven by daytime heating became
locally maximized.  This activity is now waning north/northeast of
the Black Hills vicinity, but could perhaps continue into the 02-04Z
time frame.

...As the base of a 500 mb thermal trough with temperatures near or
below -20C migrates inland, scattered thunderstorm development
appears increasingly possible west of the Washington Cascades by
04-06Z.  It is possible that boundary-layer instability may become
marginally sufficient, in the presence of moderate to strong
deep-layer mean flow and shear, to support some risk for hail and
gusty winds in stronger activity.

..Kerr.. 09/24/2020

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