RSS Mesoscale Discussions from Storm Prediction Center
No watches are valid as of Tue May 5 01:01:02 UTC 2026.
MD 0640 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR SOUTH-CENTRAL ILLINOIS AND SOUTHERN INDIANA
Mesoscale Discussion 0640
NWS Storm Prediction Center Norman OK
0629 PM CDT Mon May 04 2026
Areas affected...South-central Illinois and Southern Indiana
Concerning...Severe potential...Watch possible
Valid 042329Z - 050200Z
Probability of Watch Issuance...40 percent
SUMMARY...An isolated severe threat for large hail is expected to
continue for a few hours across south-central Illinois, and may
affect southern Indiana. The for weather watch issuance is
uncertain.
DISCUSSION...A couple cells have recently develop to the northeast
of the St. Louis metro. The activity is located along the eastern
edge of a pocket of moderate instability, where the RAP has MLCAPE
around 1000 J/kg. The storms are being supported by an area of
low-level convergence and by large-scale ascent associated with a
subtle shortwave trough, evident on water vapor imagery. The WSR-88D
VWP near St Louis has effective shear in the 30 to 40 knot range,
and the RAP shows very steep mid-level lapse rates exceeding 7.5
C/km. This should be favorable for large hail with supercells that
form. However, a capping inversion is evident over much of
southeastern Illinois and southern Indiana. Also, RAP suggests that
instability is very weak in this same area. For this reason, the
storms are expected to remain elevated, and the eastern extent of
the severe threat is uncertain.
..Broyles/Hart.. 05/04/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LMK...IND...PAH...ILX...LSX...
LAT...LON 38058802 38218956 38489008 38859021 39299012 39638974
39798899 39748736 39618654 39338617 38828613 38318631
38088688 38058802
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
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SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0752 PM CDT Mon May 04 2026
Valid 050100Z - 051200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN
KANSAS INTO NORTHERN INDIANA AND NORTHWEST OHIO...
...SUMMARY...
Widely scattered severe thunderstorms capable of large hail and
damaging wind gusts are possible from eastern Kansas into the
portions of the Ohio Valley this evening into tonight. A
conditional threat for severe storms with large to very large hail
extends into portions of southern Plains through the remainder of
the evening.
...Mid-Mississippi and Ohio Valleys....
Widely scattered, strong to severe storms are ongoing this evening
along and ahead of a progressive cold front from southern lower MI
into northern IL and far southeast IA with visible satellite
indicating additional storm attempts into portions of northern MO. A
separate area of thunderstorms is ongoing within the open warm
sector east of St. Louis where hail up two inches in diameter has
been reported. In the absence of more substantial boundary-layer
moisture content, 00z observed soundings revealed the presence of
steep low/mid-level lapse rates are largely contributing to MLCAPE
of around 1000 J/kg. Meanwhile, the accompanying kinematic
environment features a vertically veering wind profile with around
40 kt of effective bulk shear magnitudes and modestly strong
low-level shear (effective SRH of 150-200 m2/s2).
Current thinking is that ongoing storms will remain capable of
isolated occurrences of large hail and locally damaging wind gusts
for the next few hours as increasing moisture content along a
nocturnal low-level jet offsets cooling in the boundary layer. The
threat should tend to diminish overnight as the boundary layer
gradually stabilizes.
For additional information on near-term details, see MCDs 640 and
641.
...Eastern Kansas into western Missouri...
Isolated to widely scattered thunderstorms have persisted this
evening across portions of western into central KS, aided by a weak
mid-level impulse moving through the central High Plains. A number
of high-resolution models suggest that activity will intensify later
this evening into tonight as it drifts east of the I-35 corridor and
encounters an increasingly unstable air mass in place across eastern
KS into western MO. A strengthening low-level jet will enhance
moisture transport into the growing complex of storms with large
hail being the primary hazard initially. With time, the models
suggest upscale growth into one or more forward-propagating clusters
with an increased risk for damaging wind gusts.
..Mead.. 05/05/2026
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SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0430 PM CDT Mon May 04 2026
Valid 061200Z - 121200Z
...Synopsis...
An expansive positively-tilted upper trough will extend across the
Southwest to the Great Lakes region with an embedded shortwave over
the Rockies on Day 3/Wednesday. Concurrently, a broad upper-level
low over eastern Canada will encourage unsettled weather across the
Northeast with a cold front transporting plentiful moisture to
portions of the Mid-Atlantic and Southeast through Day 5/Friday.
Broader fire weather concerns may temporarily be dampened for much
of the eastern U.S. for the duration of the forecast period, given a
widespread transition to green up and expected appreciable
precipitation. An upper ridge will build across the Pacific
Northwest mid-week, resulting in above normal temperatures and dry
conditions to prevail for much of the western U.S. through the
weekend.
On Day 3/Wednesday, the upper trough will migrate atop the southern
Plains and West TX as an area of surface convergence develops east
of the Front Range. This feature is expected to send a cold front
through the TX Panhandle, while downslope westerly winds and a dry
airmass persists over West TX. Recent plentiful rainfall and
marginal fuels precludes the introduction of probabilities.
Beneath an upper ridge and northwesterly flow aloft, above normal
temperatures and a dry airmass will remain over much of the western
CONUS with sporadic areas of breezy conditions. Localized fire
weather concerns may emerge where terrain-induced winds and dry
fuels align. Farther east, persistent upper-level troughing over the
northern Plains and Upper Midwest will shunt most moisture chances
south of the area. Mostly dry and occasionally breezy conditions
will prevail, promoting localized fire weather concerns where fuels
remain dry and the green up transition has not yet occurred.
..Elizalde-Garcia.. 05/04/2026
...Please see www.spc.noaa.gov/fire for graphic product...
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