Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0303 PM CDT Sat Sep 13 2025
Valid 132000Z - 141200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
NEW MEXICO...
...SUMMARY...
Isolated severe wind and hail will be possible from the
Southwest/southern Rockies, particularly over parts of New Mexico,
into the northern Great Plains and a portion of the Midwest, mainly
this afternoon and early evening.
...20Z Update...
A few stronger elevated thunderstorms have persisted across
northwest Indiana through early afternoon. These storms appear to be
maintaining themselves as they move across western Indiana. Storms
are currently on the eastern periphery of the instability which
could limit longevity. However, strong mid-level flow is in place
(45-50 knots around 4 km per LOT VWP) which will continue to support
supercells and may help maintain storms even with limited
instability. Only a slight southeast expansion was made to the
Marginal Risk to account for areas downstream of the recently warned
storms. Will maintain the Marginal risk farther west across eastern
Illinois, but confidence is not that high that storms will form
across this area. However, if they do, the environment would support
strong to severe storms capable of large hail and wind gusts.
Farther west, scattered thunderstorms have developed across New
Mexico and are starting to move east. Weak to moderate instability
and moderate to strong shear will support some severe weather
potential with large hail and wind gusts as the primary threats. See
MCD 2071 for additional information about the threat in this area.
Across southeast Utah and southwest Colorado, several storms have
developed with some apparent supercell structures. Increased ambient
vorticity beneath the upper-level low has provided an environment
apparently favorable for tornadoes. At least one well-developed
tornado/landspout has been observed thus far. Added 2% tornado
probabilities to this region as an additional threat could be
possible from the same storm or a few other stronger cells in the
region.
..Bentley.. 09/13/2025
.PREV DISCUSSION... /ISSUED 1136 AM CDT Sat Sep 13 2025/
...New Mexico and southern Rockies/High Plains...
A prominent upper trough will continue to shift east-northeastward
today and tonight over the Four Corners area and south-central
Rockies. DPVA/cooling aloft and plentiful moisture preceding the
trough will contribute to a relatively high coverage, and
potentially multiple rounds, of thunderstorms regionally. The 12z
observed sounding from El Paso featured Precipitable Water values in
the upper 5-10 percent of daily climatological values. Ongoing
thunderstorms/cloud cover will tend to mute diurnal destabilization
in areas, but portions of southern/eastern New Mexico may see
somewhat more aggressive destabilization pending cloud breaks. Will
defer to the ample moisture/coverage of storms and rather favorable
deep-layer flow field (40+ kt effective shear) and introduce a
categorical Slight Risk for portions of New Mexico, where hail/wind
risks, including some supercells, are most probable this afternoon
through early evening.
...Northern Plains including NE/SD/ND...
It still seems that residual cloud cover/outflow from last night's
multiple rounds of thunderstorms will tend to temper destabilization
later today within a modestly-sheared environment. Nevertheless,
some isolated severe wind/hail potential will exist as storms
redevelop across the High Plains later today.
...Midwest including portions of Illinois/Indiana...
Overall severe potential should remain relatively limited (or at
least highly uncertain), however some redevelopment and/or
reintensification could occur across downstate portion of
Illinois/Indiana, and/or farther north along the instability
gradient across northeast Illinois/Chicagoland vicinity into
northwest Indiana, where some air mass recovery is plausible. Will
maintain low hail/wind probabilities regionally given some lingering
severe potential, on a more conditional/uncertain basis with
north-northwestward extent under the increasing influence of the
upper ridge.
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