RSS Mesoscale Discussions from Storm Prediction Center
WW 77 SEVERE TSTM IA IL WI LM 310220Z - 310800Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 77
NWS Storm Prediction Center Norman OK
920 PM CDT Mon Mar 30 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Iowa
Northern Illinois
Southern Wisconsin
Lake Michigan
* Effective this Monday night and Tuesday morning from 920 PM
until 300 AM CDT.
* Primary threats include...
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
Isolated damaging wind gusts to 70 mph possible
SUMMARY...Scattered strong to severe thunderstorms will increase
through late evening into the overnight across the region. Large
hail is expected to be the most common severe hazard, but isolated
damaging winds could also occur.
The severe thunderstorm watch area is approximately along and 50
statute miles north and south of a line from 55 miles west northwest
of Des Moines IA to 45 miles south southeast of Racine WI. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU7).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
26030.
...Guyer
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WW 0077 Status Updates
STATUS REPORT ON WW 77
THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.
..BENTLEY..03/31/26
ATTN...WFO...DMX...DVN...ARX...LOT...MKX...
STATUS REPORT FOR WS 77
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
ILC007-011-015-031-037-043-063-073-085-089-093-097-099-103-111-
131-141-155-161-177-195-197-201-310640-
IL
. ILLINOIS COUNTIES INCLUDED ARE
BOONE BUREAU CARROLL
COOK DE KALB DUPAGE
GRUNDY HENRY JO DAVIESS
KANE KENDALL LAKE
LA SALLE LEE MCHENRY
MERCER OGLE PUTNAM
ROCK ISLAND STEPHENSON WHITESIDE
WILL WINNEBAGO
IAC001-009-011-015-019-029-031-043-045-049-055-061-077-095-097-
099-103-105-107-113-115-121-123-125-127-139-153-157-163-169-171-
181-183-310640-
IA
. IOWA COUNTIES INCLUDED ARE
ADAIR AUDUBON BENTON
BOONE BUCHANAN CASS
CEDAR CLAYTON CLINTON
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MD 0301 CONCERNING SEVERE THUNDERSTORM WATCH 77... FOR CENTRAL IOWA TO SOUTHERN LAKE MICHIGAN
Mesoscale Discussion 0301
NWS Storm Prediction Center Norman OK
1129 PM CDT Mon Mar 30 2026
Areas affected...Central Iowa to southern Lake Michigan
Concerning...Severe Thunderstorm Watch 77...
Valid 310429Z - 310630Z
The severe weather threat for Severe Thunderstorm Watch 77
continues.
SUMMARY...Large hail threat continues with storms tonight, along
with some risk for gusty winds.
DISCUSSION...Back edge of a short-wave trough appears to extend from
southwest MN-eastern NE. Scattered deep convection has developed
ahead of this feature, partially aided by a strong but veered LLJ.
Sustained low-level warm advection will continue much of the night
along this corridor so new development is possible in addition to
the two main clusters that are currently observed. Latest MESH data
suggests large hail is noted within the stronger updrafts in these
clusters, and this should be the primary concern into the early
morning hours.
..Darrow.. 03/31/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LOT...MKX...DVN...ARX...DMX...
LAT...LON 42549463 42878745 41438746 41109466 42549463
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN
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MD 0300 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR LOWER MICHIGAN AND FAR NORTHERN INDIANA
Mesoscale Discussion 0300
NWS Storm Prediction Center Norman OK
1049 PM CDT Mon Mar 30 2026
Areas affected...Lower Michigan and far northern Indiana
Concerning...Severe potential...Watch possible
Valid 310349Z - 310615Z
Probability of Watch Issuance...40 percent
SUMMARY...Isolated severe storms mainly capable of hail should
increase through late evening into the overnight. While the need for
a Watch is uncertain, short-term trends will continue to be
monitored.
DISCUSSION...Thunderstorms have steadily increased through late
evening across the middle part of Lower Michigan. These storms are
occurring near/just north of a stationary/slow-moving warm front,
and should further increase over the next several hours via
warm/moist advection and isentropic ascent. Additional storm
development/persistence may also occur farther south across southern
Lower Michigan and far northern Indiana via storms that are
developing across northeast Illinois. Steep mid-level lapse rates
are steadily advecting eastward across the region, and strong shear
through the cloud-bearing layer will support some severe
storms/elevated supercells north of the front. Some damaging wind
potential may also exist with any storm development or persistence
into/across the southern half of Lower Michigan and/or far northern
Indiana, although increasing convective inhibition will tend to be a
detrimental factor.
..Guyer.. 03/31/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DTX...APX...IWX...GRR...LOT...
LAT...LON 44608628 44408444 44318308 43728255 43078393 41908473
41398595 41498695 43208655 44608628
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
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SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1259 AM CDT Tue Mar 31 2026
Valid 311200Z - 011200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MIDWEST EASTWARD INTO THE CENTRAL APPALACHIANS...
...SUMMARY...
Scattered severe thunderstorms with damaging wind gusts and isolated
large hail are expected today into this evening across parts of the
Great Lakes and Midwest. Isolated severe storms may also occur from
the mid to upper Mississippi Valley southwestward into the southern
and central Plains.
...Upper Midwest/Southern Great Lakes/Mid to Upper Mississippi
Valley...
An upper-level trough will move eastward into the Great Lakes today,
as a more subtle shortwave trough moves through the Midwest. At the
surface, a low will move into Lower Michigan as a trailing cold
front advances southeastward across the mid to upper Mississippi
Valley. Ahead of the front, a cluster of storms is expected to move
eastward through southern Wisconsin and northern Illinois during the
morning, reaching Lower Michigan by midday. To the south of this
cluster of storms, surface heating with dewpoints of 55 to 60 F will
contribute to a broad area of instability. An outflow boundary
appears likely to move into northern Indiana and northern Ohio
around midday, where scattered convective initiation should take
place in the early afternoon. These storms are forecast to move
eastward into the central Appalachians during the mid to late
afternoon, with additional storms forming further west across
northern Missouri and central Illinois. As cells gradually increase
in coverage during the late afternoon and early evening, MCS
development will be possible.
The greatest chance for severe storms appears likely to occur this
afternoon and evening from far northeast Illinois eastward into
western New York and northern Pennsylvania. Along much of this
east-to-west corridor, MLCAPE is forecast to increase into the 1000
to 1500 J/kg range by late afternoon. Deep-layer shear will also
increase across the Midwest as a 75 to 90 knot mid-level jet moves
into the Great Lakes. Along the southern periphery of the jet, lift
and shear will be sufficiently strong for organized storms.
Supercells and short multicell line segments, associated with severe
wind gusts and large hail, are expected from mid afternoon into the
evening. Increasing cell coverage could result in a somewhat larger
severe line segment, with damaging wind gusts as the primary threat.
Further west into the lower Missouri Valley, isolated severe storms
are expected to develop in the late afternoon and early evening.
This area will be located further from the mid-level jet, which will
make deep-layer shear and low-level flow a bit weaker. For this
reason, the severe threat is expected to remain more localized.
...Southern and Central Plains...
Southwesterly mid-level flow will remain in place over the southern
and central Plains today. At the surface, a cold front will advance
southward across the Texas Panhandle extending northeastward into
southern and eastern Kansas. Ahead of the front, surface dewpoints
in the 55 to 60 F range will contribute to the development of
moderate instability by afternoon, with MLCAPE rising into the 1500
to 2000 J/kg range. As low-level convergence increases along and to
the south of the front, isolated to scattered thunderstorms will
form. RAP forecast soundings near the instability axis late this
afternoon have large surface temperature-dewpoint depressions with
very steep low to mid-level lapse rates. This will result in
high-based storms that could be capable of producing isolated severe
wind gusts and hail. The threat should persist into the evening.
..Broyles/Squitieri.. 03/31/2026
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