Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1234 AM CDT Mon Apr 13 2026

Valid 131200Z - 141200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE UPPER MISSISSIPPI RIVER VALLEY...

...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. A more conditional and isolated risk
for severe storms is possible across portions of the southern Plains
late this afternoon and evening.

...Synopsis...
Early-morning water-vapor imagery depicts an upper trough with
multiple embedded vorticity maxima over the Great Basin. While the
primary upper wave will remain over the West for today, a leading
impulse is forecast to eject towards the northern Plains and into
the Great Lakes through tonight. At the surface, a weak lee cyclone
over the central High Plains will migrate northeastward in tandem
with the upper impulse, likely reaching the southern MN vicinity by
early evening. As this occurs, a plume of mid-60s dewpoints will
spread north into the upper MS Valley along and south of a warm
front. Scattered thunderstorm development along and north of the
warm front is anticipated by late afternoon as forcing for ascent
gradually increases. Elsewhere, more isolated strong to severe
thunderstorms are possible across portions of TX and OK where deep
mixing along a dryline may result in sustained deep convection. 

...Upper MS Valley...
A combination of shortwave ridging and capping at the base of an EML
will limit thunderstorm development through much of the day across
southern MN into central WI. This will allow for continued moisture
return as a warm front lifts into the region with MLCAPE values
forecast to reach 2000-2500 J/kg by around 21 UTC. Thunderstorm
development will become increasingly probable through the 21-00 UTC
period as isentropic ascent strengthens ahead of the approaching
upper disturbance. Lingering inhibition coupled with 45-50 knot
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 with the more robust cells. Additionally, enhanced low-level
SRH along the frontal zone may result in a corridor of relatively
higher tornado potential if convection can remain rooted along the
boundary. 

While the overall environment appears very favorable for intense
convection, east/northeasterly storm motions along or just north of
the warm front will likely promote storm advection towards the cool
side of the boundary and clustering/upscale growth through the
evening. This, combined with capping over the remainder of the warm
sector, limits confidence in a more widespread tornado threat, and
could modulate the potential for significant (2+ inch) hail within a
few hours after convective initiation. Nonetheless, a corridor of
higher hail potential remains evident in latest guidance along and
just north of the warm front where discrete supercells are most
probable. 30% hail probabilities have been shifted to reflect a
southward trend in frontal placement noted in most recent guidance.

...Southern Plains...
A moist and very unstable air mass will remain in place across TX
and OK today with MLCAPE values expected to increase to around 2500
J/kg by late afternoon. Ample diurnal heating/mixing on the western
periphery of the moisture plume will likely result in weak,
high-based convection by mid to late afternoon. Easterly storm
motions may promote downstream intensification as convection
migrates towards richer low-level moisture, but this will be
conditional on convection remaining sustained long enough to realize
the favorable thermodynamic environment. If this can occur,
deep-layer shear values on the order of 40 knots should promote
organized convection - likely in the form of supercells - with an
attendant threat for all hazards, including very large hail. While
both global and CAM ensemble guidance hint at this potential, the
lack of appreciable lifting mechanisms (aside from the dryline
circulation/boundary-layer mixing) casts considerable uncertainty on
overall storm coverage.

..Moore/Wendt.. 04/13/2026

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
0104 AM CDT Mon Apr 13 2026

Valid 141200Z - 151200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF IOWA INTO NORTHERN ILLINOIS AND SOUTHERN WISCONSIN...

...SUMMARY...
Isolated to scattered severe thunderstorms are expected on Tuesday
and Tuesday night from the Southern Plains to the Great Lakes. Large
to very large hail, a few tornadoes, and damaging wind gusts will be
possible, particularly across parts of eastern Iowa, northern
Illinois, and southern Wisconsin. Additional strong storms, mainly
producing strong wind gusts, will be possible across parts of the
Northeast.

...Synopsis...

A broad swath of enhanced deep-layer southwesterly flow will
overspread the southern High Plains to the Great Lakes on Tuesday.
An upper shortwave trough over the Great Basin will slowly pivot
east through the period, emerging over the central/southern High
Plains by Wednesday morning. A weak shortwave impulse is also
forecast to move across the northern Plains and Upper Midwest. At
the surface, low pressure will be centered over the Mid-MO Valley
for much of the period, with a warm front extending east/northeast
from north-central IA into southern WI and central Lower MI.
Meanwhile, a dryline will extend southwest across eastern KS into
western TX. Ahead of these boundaries, a seasonally moist airmass
will be in place, with mid-60s dewpoints common. The aforementioned
surface boundaries will become a focus severe thunderstorm
development Tuesday afternoon into the nighttime hours.

...Mid-MS Valley and Great Lakes vicinity...

A severe risk is expected to develop by late afternoon within the
warm frontal zone from Iowa into northern IL/southern WI in a
persistent warm advection regime. While height tendencies are
forecast to remain mostly neutral, low-level convergence along the
boundary and a glancing influence from a weak shortwave impulse
migrating across the northern Plains into northern MN/Upper MI
should provide focused ascent. A southwesterly 850-700 mb jet is
also forecast to increase across the region by late afternoon into
evening. Cool temperatures aloft (around -16 C at 500 mb) and steep
midlevel lapse rates atop a moist boundary layer will support MLCAPE
around 2000-3000 J/kg amid elongated/straight hodographs. As a
result, large to very large hail will be possible with initial
supercell thunderstorms. Storm motion and southwesterly deep-layer
flow may result in convection moving to the cool side of the warm
front. Even so, elevated storms will pose a risk for significant
hail. With time, and as the low-level jet increases during the
evening, convection may consolidate/grow upscale into one or most
bowing segments and progress eastward into Lower MI/IN/OH, posing a
continued risk for hail and an increasing risk for damaging wind
gusts.

Any supercells that develop and can be sustained within the warm
sector will also pose a risk for a few tornadoes (some strong), very
large hail and damaging gusts.

...Southern Plains into eastern KS/western MO...

Moderate destabilization is forecast along the surface dryline by
afternoon. Strong heating along/just west of the dryline will
promote mixing, while low-level confluence and subtle height falls
(by 21-00z) provide sufficient forcing for ascent for isolated
thunderstorm development. Supercell wind profiles will be present
amid steep midlevel lapse rates and elongated hodographs. Large to
very large hail, locally strong wind gusts and a couple of tornadoes
will be possible. Storms should develop northward during the evening
into eastern KS and western MO as the low-level jet increases.

...Northeast...

Rounds of thunderstorms are expected during the afternoon and
evening within a warm advection regime. MLCAPE should increase to
around 1000 J/kg within a moistening low-level airmass. Strong
deep-layer westerly flow and steepening low-level lapse rates will
support isolated strong wind gusts across the region.

..Leitman.. 04/13/2026

Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1246 AM CDT Mon Apr 13 2026

Valid 131200Z - 141200Z

...CRITICAL FIRE WEATHER AREA FOR EASTERN WYOMING...SOUTHWESTERN
SOUTH DAKOTA...NORTHWESTERN NEBRASKA...
...CRITICAL FIRE WEATHER AREA FOR SOUTHEASTERN COLORADO AND ADJACENT
HIGH PLAINS...

...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.

..Wendt.. 04/13/2026

...Please see www.spc.noaa.gov/fire for graphic product...