Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0749 AM CDT Thu Sep 18 2025
Valid 181300Z - 191200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM OK INTO THE
OZARKS AND LOWER MO VALLEY...AND ACROSS PORTIONS OF SOUTHERN CA AND
SOUTHWEST AZ...
...SUMMARY...
Strong to locally severe storms are possible from late afternoon
into tonight from parts of Oklahoma into Missouri and over small
parts of adjacent states. Isolated strong to severe storms are
possible across eastern southern California and southwest Arizona as
well.
...Southern CA/Southwest AZ...
Anomalously moist airmass associated with the remnants of tropical
cyclone Mario continues to advect northward into southern CA/AZ. 12Z
NKX sounding sampled a 1.95 PWAT, which is well above the 90th
percentile based on SPC sounding climatology. Filtered heating is
anticipated within this moist environment, resulting in moderate
buoyancy across much of eastern southern CA and southwest AZ this
afternoon. Moderate vertical shear is anticipated as well,
particularly across eastern southern CA. Thunderstorm development is
expected during the afternoon, with a predominantly multicellular
mode. However, enough shear and instability are in place to support
organization with any more persistent updrafts, and a few supercells
capable of damaging gusts are possible.
A very-low-probability tornado threat exists as well, particularly
in the Lower CO Valley vicinity where some guidance suggests surface
winds stay more southeasterly. Even so, the low-level flow is weak
and any tornado threat should be very localized.
...Central/Southern Plains into Ozarks and Mid/Lower MO Valley...
Broad upper troughing remains in place across the northern/central
Plains, anchored by a pair of modest cyclones, one currently
centered over central SD and the other centered over the MT/SK
border vicinity. Another shortwave trough is rotating through the
base of this troughing, and is forecast to progress
eastward/southward into KS and northern OK today before pivoting
into IA/MO/AR during tonight.
Surface analysis reveals a pair of lows, one beneath the central SD
cyclone and another weaker one over northeast OK. Modest troughing
extends between these lows and a diffuse cold front extends
southwestward from the northeast OK low into the TX South Plains.
Mid 60s dewpoints currently extend through much of eastern KS and
western MO.
A modest eastward/southeastward push of the cold front/surface
trough is expected as the shortwave trough moves into KS, with
ascent attendant to these features resulting in thunderstorm
development from the Mid MO Valley across eastern KS/western MO into
central OK and far northwest TX. Highest coverage appears most
likely from far eastern KS into western MO, northeast OK, and
northwest AR. Buoyancy and shear will both be fairly modest.
However, strong high-level flow may support a greater chance of hail
from the TX Panhandle into OK, while the coldest midlevel
temperatures also support hail from eastern KS into MO.
..Mosier/Bentley.. 09/18/2025
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