Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1244 AM CDT Sat Sep 13 2025
Valid 131200Z - 141200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
SOUTHWEST TO THE DAKOTAS AND IN A PART OF THE MIDWEST...
...SUMMARY...
Isolated severe wind and hail will be possible from the
Southwest/southern Rockies to the northern Great Plains and a
portion of the Midwest, mainly today into early tonight.
...Southwest/southern Rockies/High Plains...
The basal portion of the broad mid/upper trough from the northern
Rockies to the Lower CO Valley will progress more quickly east,
yielding an elongated trough enveloping the entire High Plains by
early Sunday. Widespread thunderstorm development is anticipated by
midday to early afternoon across western NM/CO as cooling mid-level
temperatures become favorably timed with moderate diurnal heating of
a seasonably moist airmass. Lower-level instability should be
tempered by remnants of early morning convection and the quick
redevelopment cycle by afternoon. Nevertheless, a broad belt of
moderate southwesterly speed shear should support transient
mid-level updraft rotation within the deepest updrafts. These should
tend to become focused across southern/eastern NM later in the
afternoon, but this region will be on the fringe of greater
mid-level cooling centered on the Four Corners. As such, mid-level
lapse rates will be weak where boundary-layer heating is more
pronounced. A broad swath of sporadic strong to marginally severe
hail/wind is anticipated before convection subsides after sunset.
...NE/SD/ND...
Overall severe wind/hail potential appears low across multiple
regimes through the period, amid a persistent meridional mid-level
flow regime. Ongoing convection over the western Dakotas, tied to a
minor MCV, should progress north-northeast towards the Canadian
border this morning. Residual cloudiness/overturning should limit
the northern extent of more substantial diurnal destabilization in
ND. Late afternoon to evening storm development appears more likely
to emanate out of the central High Plains north-northeastward across
western/central NE within a modestly sheared and weakly buoyant
airmass. This activity may foster another MCV that drifts north into
SD, which could impinge on a confined corridor of recovered moderate
buoyancy and sustain a marginal severe wind/hail threat tonight.
...IL/IN/WI...
Low-probability severe hail/wind potential remains evident, but
seems likely to be rather isolated. An MCV over central WI will
drift south-southeast this morning. An increase in convective vigor
is possible towards sunrise along the MUCAPE gradient in southern WI
to northern IL. Within a belt of moderate mid-level northwesterlies,
transient/weak updraft rotation is possible in a cell or two.
Guidance differs greatly on the degree of boundary-layer heating
downstream of the morning elevated activity. The more aggressively
warm guidance suggests a conditional threat of diurnal
intensification with potential for locally strong gusts.
..Grams/Dean.. 09/13/2025
Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/TN369M
