LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1247 AM CDT Mon Aug 21 2023
Valid 211200Z - 221200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE INTERIOR WEST...UPPER MIDWEST...AND THE LOWER TEXAS COAST...
...SUMMARY...
Locally severe thunderstorms are possible across parts of the
Interior West mainly during the afternoon, parts of the Upper
Midwest and lower Texas coast overnight.
...AZ north through the eastern Great Basin into MT...
The eastern periphery of the extratropical remnants of tropical
cyclone Hilary, abutted to a central U.S. mid-level anticyclone,
will yield a tightened gradient and stronger flow across this
elongated south to north region. Scattered thunderstorms are
forecast to develop during the afternoon owing to cloud
breaks/heating and steepened low-level lapse rates. A few strong to
locally severe gusts may occur with the more intense thunderstorm
clusters before this activity weakens during the evening.
...Lower TX coast...
Model guidance shows an area of organizing low pressure over the
central Gulf of Mexico moving westward into the western half of the
Gulf during the period, to the south of a mid-level high located
over the lower MO Valley. Strengthening easterly low-level flow and
enlarging hodographs are forecast to penetrate the beaches and the
near shore areas of the lower TX coast and TX coastal bend late
tonight. Forecast soundings show weak buoyancy due in part to
mid-upper 70s surface dewpoints. A few transient supercells are
possible beginning around 06z through early Tuesday morning.
...Upper Midwest...
A belt of strong mid to high-level westerly flow will extend from
the southern Prairie provinces east-southeastward into the Upper
Great Lakes, to the north of a mid-level anticyclone centered over
MO. A surface front will be draped west-east over the upper MS
Valley. A southwesterly LLJ will strengthen tonight from the
central High Plains northeastward into MN. This will favor ascent
north of the surface boundary, and result in isolated to scattered
thunderstorms developing primarily after 04z. Marginally severe
hail may accompany the stronger cores.
..Smith/Weinman.. 08/21/2023
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