RSS Mesoscale Discussions from Storm Prediction Center
No watches are valid as of Mon Apr 13 16:05:02 UTC 2026.
MD 0395 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF EXTREME EASTERN IOWA INTO WESTERN...CENTRAL...AND NORTHERN ILLINOIS
Mesoscale Discussion 0395
NWS Storm Prediction Center Norman OK
1103 AM CDT Mon Apr 13 2026
Areas affected...portions of extreme eastern Iowa into
western...central...and northern Illinois
Concerning...Severe potential...Watch possible
Valid 131603Z - 131730Z
Probability of Watch Issuance...40 percent
SUMMARY...Some hail (possibly over 1 inch in diameter) may occur
with gradually intensifying storms over the next few hours. It is
unclear if these storms will pose the greatest severe risk this
afternoon, or if the greater risk will occur with later storms.
DISCUSSION...850 mb troughing is underway across the Plains states
into the Midwest, with 15Z mesoanalysis showing the northeasterly
terminus of a LLJ currently positioned along the IA/IL/MO border.
Here, an 850 mb Td gradient exists, with modest WAA likely
supporting the gradual intensification of elevated convection within
this regime. The 12Z ILX observed sounding and 15Z mesoanalysis
depicts 700-500 mb lapse rates in the 8-8.5 C/km range, contributing
to MUCAPE approaching 2000 J/kg. These storms are encroaching on a
region of stronger 500 mb southwesterly flow, driven by a departing
upper trough over the eastern U.S., which is resulting in 30-40 kt
of effective bulk shear ahead of the storms. If storms continue to
intensify, it is plausible that at a hail threat may materialize
over the next few hours, with some stones potentially exceeding 1
inch in diameter.
Short-range high resolution ensemble guidance is providing mixed
signals regarding the evolution of this convection. Some
deterministic CAMS show that the ongoing storms eventually
consolidate and develop into stronger supercell structures in
northern IL by afternoon. Other guidance members depict the ongoing
storms oscillating in intensity, while stronger storms develop
later. As such, there is an appreciable degree of uncertainty as to
the evolution of the longer term severe threat with these WAA
storms. All this being said, convective trends will continue to be
monitored for the need of a WW issuance.
..Squitieri/Guyer.. 04/13/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LOT...ILX...LSX...DVN...
LAT...LON 40829153 41349115 41809076 42269021 42318942 42178872
41918839 41478835 41028850 40608866 40238895 40058932
39988999 40039043 40249121 40829153
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
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SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0800 AM CDT Mon Apr 13 2026
Valid 131300Z - 141200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN
MINNESOTA AND PARTS OF WISCONSIN...
...SUMMARY...
Severe thunderstorms are likely across the Upper Mississippi Valley
and Great Lakes region with potential for large to very large hail,
damaging wind, and tornadoes, mainly late this afternoon into
tonight. A more conditional and isolated risk for severe storms is
possible across portions of the southern Plains late this afternoon
and evening.
...Upper Mississippi Valley/Great Lakes including MN/WI...
Multiple lead mid-level disturbances over the northern High Plains
will progress northeastward today toward the Upper Midwest, with
strengthening winds aloft across this region particularly late today
and tonight. A surface low will tend to deepen/develop
east-northeastward from northeast Nebraska this morning into far
southern Minnesota and Wisconsin by tonight in vicinity of a
slow-moving/stalled frontal boundary. Low/middle 60s F surface
dewpoints will advect north-northeastward and become increasingly
prevalent along/south of the aforementioned stationary/warm front
this afternoon. MLCAPE values are forecast to reach 2000-2500 J/kg
by around 21z/4pm CDT.
Thunderstorm development will become increasingly probable through
mid/late afternoon (21-00z) as isentropic ascent strengthens ahead
of the approaching upper disturbance. Lingering inhibition coupled
with 45-50 kt effective bulk shear should promote initially discrete
supercells along or just north of the surface boundary. Hodograph
elongation appears favorable for a large hail threat, possibly as
large as 2-3 inches in diameter with the more robust cells.
Additionally, enhanced low-level SRH along the frontal zone is
expected to result in a corridor of relatively higher tornado
potential for storms that can remain rooted immediately along the
boundary.
While the overall environment appears very favorable for intense
convection/supercells, east-northeasterly storm motions along or
just north of the warm front will likely promote clustering/upscale
growth through the evening, with an increasing damaging wind
potential and a continued tornado risk via line-embedded circulation
potential.
...Northern Illinois/northern Indiana and southern Lake Michigan...
There is the potential that a somewhat separate corridor of
severe-weather potential may unfold today, potentially born out of
subtle mid-level wave and early morning convection across northeast
Missouri vicinity and/or development later today. The initially
elevated storms would be on the edge of the
east/northeastward-advecting elevated mixed layer. Steep mid-level
lapse rates and 35+ kt effective shear could support initially
isolated hail potential, but a more organized surface-based severe
risk could manifest if some of the more-aggressive early morning
short-term guidance trends materialize (HRRR/RAP/RRFS).
...Southern Plains including Oklahoma/Texas...
A moist and potentially unstable air mass will persist regionally to
the east of a dryline located around peak heating from east-central
Kansas south-southwestward into west-central Oklahoma and western
north Texas to the Texas Big Bend vicinity. Immediately east of the
dryline, warm-sector dewpoints are expected to generally be in the
middle 60s F, supporting MLCAPE values to 2500-3000 J/kg.
The extent/likelihood of sustained deep convection later today is a
key question. The primary southern-stream trough will be well
upstream over the southwest Desert, with neutral height tendencies
across the southern Plains, although early morning water vapor
imagery and derived wind data suggest that a subtle disturbance over
northern Mexico and the southern Rockies could approach the
dryline/warm sector later today.
Regardless, ample post-dryline mixing and near-dryline
confluence/weak convergence may be sufficient for deep convective
initiation after 21z/4pm CDT, at least an isolated basis. Forecast
mass fields would imply that this is most probable across
central/southwest Oklahoma into the north Texas Big Country, and
perhaps somewhat separately across the Texas Big Bend and Rio Grande
vicinity.
If/where storms develop and mature, deep-layer shear on the order of
40+ kt will support supercells, potentially capable of all hazards
including very large hail. An increased confidence in deep
convective initiation late this afternoon/early evening could
warrant focus Slight Risk delineations in subsequent Day 1 updates.
...Northern High Plains...
Generally isolated severe storms capable of hail/wind will be
possible late this afternoon into evening along/north of the surface
front where modest low-level moisture and vertical shear will be
maximized, in the presence of steep low/mid-level lapse rates.
..Guyer/Broyles.. 04/13/2026
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SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1058 AM CDT Mon Apr 13 2026
Valid 131700Z - 141200Z
...CRITICAL FIRE WEATHER AREA FOR EASTERN WYOMING...SOUTHWESTERN
SOUTH DAKOTA...NORTHWESTERN NEBRASKA...
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SOUTHERN PLAINS...
...Southern Plains...
Critical fire weather highlights have been expanded farther east to
account for expected stronger afternoon winds and very low RH
overlapping a region of receptive fuels and exceptional fuel
loading. Current observations portray an eastward progressing
dryline into western OK, with RH already dropping to below 20
percent and sustained southwesterly winds increasing to 20 mph
behind the dryline. As cloud cover decreases this morning, deeper
mixing will encourage surface wind gusts of up 30-35 mph and
decreasing RH to less than 15 percent, heightening fire spread
concerns.
The rest of the forecast remains on track, see the previous
discussion for more information.
..Elizalde-Garcia/Williams.. 04/13/2026
.PREV DISCUSSION... /ISSUED 1246 AM CDT Mon Apr 13 2026/
...Synopsis...
Continued southwesterly flow aloft is expected today across much of
the central/southern Plains. A shortwave trough is expected to
approach the southern Plains very late in the period. A weaker
shortwave trough in the central Northern Plains will also be
present. At the surface, a broad area of low pressure will exist
east of the terrain.
...Eastern Wyoming into western South Dakota and Nebraska...
The northern stream mid-level jet will be favorably timed with
afternoon heating/minimum RH. This feature, coupled with the surface
trough to the east, will drive 20-25 mph winds in eastern portions
of Wyoming and adjacent western South Dakota and Nebraska. RH will
likely fall to 10-15%. Critical fire weather is expected for a few
hours during the afternoon. Farther south into the Front Range,
winds will be weaker leading to elevated fire weather.
...Southeast Colorado and vicinity...
The position of a modest surface low in southeast Colorado will
promote surface winds of around 20 mph despite the stronger
mid-level winds lagging farther southwest. Terrain enhancement could
also lead to local corridors of stronger winds. RH of around 15% is
expected during the afternoon. These conditions will support
critical fire weather.
...Piedmont...southern Appalachians...
Dry return flow around a surface high pressure system will promote
10-15 mph winds within parts of the southern Appalachians and the
Piedmont region. RH of near 20% is possible in parts of the
Mid-Atlantic though higher values of 25-35% are expected with
southward extent. Given how dry fuels are, elevated fire weather
conditions are expected.
...Please see www.spc.noaa.gov/fire for graphic product...
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