Subj : DAY2SVR: Marginal Risk SW
To   : All
From : Mike Powell
Date : Thu Aug 31 2023 07:32:00

ACUS02 KWNS 310602
SWODY2
SPC AC 310600

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Thu Aug 31 2023

Valid 011200Z - 021200Z

....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHWEST AND GREAT BASIN...

....SUMMARY...
Isolated strong to severe thunderstorms may occur Friday across
parts of the Southwest and Great Basin. Occasional severe wind gusts
appear to be the main threat.

....Southwest/Great Basin...
An upper trough/low is forecast to continue moving slowly southward
along/near coast of OR and northern CA. Strong mid-level
southwesterly flow attendant to this upper trough will overspread
much of the Great Basin through the day. This will contribute to
increasing deep-layer shear across parts of NV/UT and ID through
Friday afternoon, decreasing with southward extent into the Lower CO
River Valley and AZ. Greater low-level moisture, with at least low
to mid 60s surface dewpoints, should generally remain confined to
parts of southeastern CA and the lower elevations of AZ. Still, some
northward low-level moisture advection should occur across pats of
the Great Basin ahead of a surface low. Even modest daytime heating
should contribute to weak destabilization with northward extent
across NV/UT and into parts of southeastern ID.

General consensus from high-resolution guidance is for a gradual
uptick in convective coverage and intensity to occur from parts of
southeastern CA and western/central AZ northward into eastern NV and
western UT Friday afternoon and evening. Multicell clusters should
be the dominant convective mode given around 25-35 kt of effective
bulk shear forecast. Thunderstorms may be less organized with
southward extent into AZ, but greater instability and steeper
low-level lapse rates may help compensate to some extent. Isolated
strong to severe wind gusts may occur with any of these clusters as
they spread generally north-northeastward through the evening hours.
Eventually, these thunderstorms should weaken with eastward extent
with the loss of daytime heating, and as they move into a less
favorable thermodynamic environment.

...Gleason.. 08/31/2023

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