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.
$$
423
ACUS02 KWNS 131730
SWODY2
SPC AC 131729
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1229 PM CDT Sat Sep 13 2025
Valid 141200Z - 151200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE NORTHERN PLAINS EXTENDING INTO THE SOUTHERN HIGH PLAINS...
...SUMMARY...
Isolated severe storms are possible across parts of the northern
Plains into the southern High Plains tomorrow (Sunday).
...Synopsis...
A broad negative tilt trough will eject into the central Plains on
Sunday, resulting in a deepening a surface low across the Dakotas.
As the surface low deepens, the southerly low-level jet will
increase with warm and moist advection from the southern Plains into
the northern Plains.
...Great Plains States...
The broad area of warm and moist advection will result in widespread
shower/thunderstorm activity ongoing at the start of the period
Sunday morning. In the wake of this morning convection, extensive
cloud cover is expected to cover much of the region from the central
Plains into the northern Plains. Some breaks in the cloud cover may
allow for pockets of heating and recovery, but it remains uncertain
how much air mass recovery will be achieved. Forecast soundings
indicate tall skinny CAPE profiles and modest lapse rates (6-7 C/km)
which may produce narrow updrafts that struggle to maintain
intensity.
Nonetheless, sufficient deep layer shear around 30-40 knots will
support potential for a few organized storms to develop where
recovery occurs, with development of multi-cell clusters and perhaps
a few supercells. A narrow Marginal Risk was maintained across the
Plains where redevelopment is most likely to start in the northern
Plains and spread southward through the afternoon/evening. Closer to
surface low across the Dakotas and on the nose of the low-level jet
axis, a conditional risk for a tornado is possible if a supercell
can be maintained. Overall, the main risks will be for sporadic
strong to severe wind and hail.
..Thornton.. 09/13/2025
$$
341
ACUS03 KWNS 131923
SWODY3
SPC AC 131923
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0223 PM CDT Sat Sep 13 2025
Valid 151200Z - 161200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Organized severe thunderstorm potential appears generally low on
Monday.
...Synopsis and Discussion...
The severe threat will remain low on Monday across the CONUS. A pair
of weakening upper lows will shift northward across the Northern
Rockies into Canada with westerly flow across the Plains and a
building high across the eastern US. A weak surface low should
develop northward from ND into Manitoba by Monday evening, with a
weak front extending southward from this low across parts of the
northern/central Plains. While widely scattered thunderstorm
development is expected across the central/northern Plains across a
moderately unstable warm sector, shear will be displaced to the
north with the upper-level flow which should limit any organized
severe threat.
Elsewhere, a few thunderstorms are also expected to develop across
the southern High Plains near the surface trough. Forcing and shear
for organization will also be negligible in this region. Widespread
thunderstorms are also expected near the upper-lows across the
northern Rockies. Weaker instability and weak shear in this region
will keep severe potential low.
..Thornton.. 09/13/2025
$$
864
ACUS48 KWNS 130756
SWOD48
SPC AC 130754
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0254 AM CDT Sat Sep 13 2025
Valid 161200Z - 211200Z
...DISCUSSION...
Weak mid/upper-level troughing should continue to move slowly
eastward from the northern Rockies/High Plains into the central
Plains and Upper Midwest from Day 4/Tuesday into Day 5/Wednesday.
Thunderstorms should develop across these regions both days as a
surface cold front likewise develops east-southeastward. While
moderate to locally strong instability may develop across the warm
sector each afternoon, mid-level flow and related deep-layer shear
are expected to remain rather modest. This should tend to limit
updraft organization and intensity to some extent, although
isolated/marginal severe potential may necessitate low severe
probabilities in later outlooks.
By late next week into the following weekend (Day 6/Thursday to Day
8/Saturday), medium-range guidance begins to diverge in its
depiction of the evolution of upper troughing across the Midwest/OH
Valley into the eastern CONUS. This lowers confidence in the
predictability of organized severe thunderstorms, but some potential
for strong thunderstorms may exist across portions of these regions
along/ahead of an advancing cold front.
