LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0755 AM CDT Sat Jul 22 2023
Valid 221300Z - 231200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL
PLAINS AND SOUTHEAST...
...SUMMARY...
Strong to severe thunderstorms capable of large hail and damaging
winds are expected later today into this evening across the central
Plains to Upper Midwest, while other severe storms will be possible
across the Southeast States and southern Arizona.
...South-central Plains/Mid-Missouri Valley/Upper Midwest...
Weak height rises are expected owing to the building Western States
upper ridge as a belt of moderately strong northwesterly winds aloft
otherwise prevails across these regions. A moist airmass will remain
in place particularly across the south-central Plains and middle
Missouri Valley near and to the southeast of a weak front/wind shift
and a subtle surface wave across Minnesota.
Multiple preferred corridors of potential severe storm development
into this afternoon are probable, including Minnesota as well as
southern Nebraska and northwest/western Kansas near the
aforementioned boundaries, aided by subtle southeastward-moving
perturbations located across eastern Montana and southern Manitoba
early this morning. A regionally maximized combination of moderate
to locally strong buoyancy and 30-40 kt effective shear is expected
by peak heating across southern Nebraska and western/northern
Kansas, where isolated/widely scattered supercells capable of large
hail may occur aside from some persist southeastward-moving small
clusters capable of damaging winds through evening.
Across the Upper Midwest, even with more modest buoyancy (1000-1500
J/kg MLCAPE) and weaker deep-layer shear, some storms capable of
hail/damaging winds will be possible across southern/eastern
Minnesota and western Wisconsin.
Additional storm development is expected by late afternoon/early
evening across the Raton Mesa vicinity and possibly into the nearby
Texas/Oklahoma Panhandles. Wind profiles could support some brief
supercell structures with any development across/into the
Panhandles, but south/southeastward-moving clusters are otherwise
expected across the region with some hail and severe-caliber wind
gusts possible through evening.
...Southeast States...
A belt of cyclonically curved and moderately strong westerlies will
continue to reside across the region today. A surface wave will
persist and potentially somewhat deepen across the coastal Carolinas
today, while a west/southwestward-extending front otherwise settles
southward across Louisiana-Mississippi-Alabama-Georgia. A very moist
air mass near/south of the front will steadily destabilize today,
with the strongest destabilization /3000+ J per kg MLCAPE/ expected
across downstate portions of Louisiana-Mississippi-Alabama-Georgia.
With seasonally strong westerlies aloft at least partially atop the
frontal zone, effective shear of 30-35 kt will allow for scattered
sustained multicells and well-organized clusters as storms increase
in coverage and intensity into the afternoon. Damaging winds are the
most probable hazard this afternoon and early evening.
...Southern Arizona...
Clouds may linger particularly during the first part of the day, but
a moderately moist airmass and ample heating will allow for the
boundary layer to destabilize into the afternoon with thunderstorm
development expected especially across southeast Arizona
mountains/higher terrain, and to some extent across the Rim. A
modest strengthening of easterly mid-level winds may occur late
today on the immediate southern periphery of the upper ridge, which
would be favorable for storm propagation onto the desert floor, with
the potential for strong gusty outflow winds and blowing dust.
..Guyer/Mosier.. 07/22/2023
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