WW 519 SEVERE TSTM MI WI LM 271340Z - 272000Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 519
NWS Storm Prediction Center Norman OK
840 AM CDT Mon Jul 27 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Western Upper Michigan
Northeast Wisconsin
Lake Michigan
* Effective this Monday morning and afternoon from 840 AM until
300 PM CDT.
* Primary threats include...
Scattered damaging wind gusts to 70 mph possible
Scattered large hail events to 1.5 inches in diameter possible
SUMMARY...A cluster of intense thunderstorms along the
Wisconsin/Michigan border will track southeastward through the late
morning, posing a risk of damaging winds and hail.
The severe thunderstorm watch area is approximately along and 55
statute miles east and west of a line from 55 miles north northeast
of Rhinelander WI to 20 miles east southeast of Manitowoc WI. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU9).
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.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 518...
AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
31030.
...Hart
WW 0519 Status Updates
STATUS FOR WATCH 0519 HAS NOT BEEN ISSUED YET
WW 0518 Status Updates
STATUS REPORT ON WW 518
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 35 NNW EAU
TO 40 SW ASX TO 45 WNW CMX.
..WENDT..07/27/26
ATTN...WFO...MQT...DLH...FGF...GRB...
STATUS REPORT FOR WS 518
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
MIC053-131-271440-
MI
. MICHIGAN COUNTIES INCLUDED ARE
GOGEBIC ONTONAGON
WIC003-037-041-051-067-069-075-078-083-085-099-113-115-125-
271440-
WI
. WISCONSIN COUNTIES INCLUDED ARE
ASHLAND FLORENCE FOREST
IRON LANGLADE LINCOLN
MARINETTE MENOMINEE OCONTO
ONEIDA PRICE SAWYER
SHAWANO VILAS
LSZ240-241-242-271440-
CW
MD 1760 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR SOUTHEAST WI...NORTHEAST IL...SOUTHWEST LOWER MI...NORTHEAST IN
Mesoscale Discussion 1760
NWS Storm Prediction Center Norman OK
0940 AM CDT Mon Jul 27 2026
Areas affected...southeast WI...northeast IL...southwest Lower
MI...northeast IN
Concerning...Severe potential...Watch possible
Valid 271440Z - 271715Z
Probability of Watch Issuance...60 percent
SUMMARY...Severe potential will increase into early afternoon across
the Lake Michigan vicinity. Timing and storm evolution is a bit
uncertain, but a severe thunderstorm probably will be needed in the
next few hours.
DISCUSSION...A developing bow is currently moving across northeast
WI. Additional convection is developing ahead of this feature to the
southeast from Green Bay into central Lake Michigan along a moisture
and differential heating band within stronger northwesterly flow
aloft. Further south across parts of southern WI into northern IL,
elevated convection and developing TCU are noted in latest radar and
visible satellite imagery within a corridor of extreme instability.
It is possible that multiple clusters of strong to severe storms
could develop within these two corridors as the furthest north
cluster also continues to intensify and develop southeast.
While its remains unclear exactly how the risk will evolve over the
next few hours, it seems likely that storms will develop within a
very unstable airmass characterized by 2000-4000 J/kg MLCAPE, very
steep midlevel lapse rates, and 50+ kt deep-layer shear. The most
favorable corridor through early afternoon for severe storms
producing swaths of damaging winds and isolated hail will be from
eastern parts of WI into northeast IL, southern/central Lake
Michigan, and southwest Lower MI/northwest IN. Timing of watch
issuance is uncertain, but a severe thunderstorm watch will likely
be needed at some point by midday/early afternoon.
..Leitman/Hart.. 07/27/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...IWX...GRR...GRB...LOT...MKX...
LAT...LON 44948764 43908676 42968600 42508573 41988565 41148650
41138732 41478805 42108900 42788924 43668913 44568838
44948764
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
MD 1759 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR NORTHEAST ILLINOIS INTO NORTHERN INDIANA AND SOUTHWEST LOWER MICHIGAN
Mesoscale Discussion 1759
NWS Storm Prediction Center Norman OK
0752 AM CDT Mon Jul 27 2026
Areas affected...Northeast Illinois into Northern Indiana and
southwest lower Michigan
Concerning...Severe potential...Watch possible
Valid 271252Z - 271445Z
Probability of Watch Issuance...40 percent
SUMMARY...A watch is possible this morning for the lower Lake
Michigan vicinity, though uncertainty remains high. Convective
trends will need to be monitored this morning.
DISCUSSION...Current radar CAPPI trends suggest that the storm
ongoing in southwest lower Michigan has trended down in intensity
over the past 30 minutes. That said, model guidance such as the RRFS
and HRRR continue to highlight the southern Lake Michigan vicinity
as an area for possible development/intensification later this
morning. Objective mesoanalysis shows strong to extreme buoyancy
across northern Illinois into parts of northern Indiana. Morning
observed soundings from the region show similar MLCAPE values as
well as steep mid-level lapse rates and strong shear. Forcing for
ascent will be nebulous and cloud cover/capping also limits
confidence on where, or if, additional severe storms will develop
later this morning. However, visible satellite trends show areas of
convective turrets from northeast Illinois into southern Lake
Michigan. This area will need to be monitored for a possible watch
though uncertainty in this scenario is admittedly high.
..Wendt/Guyer.. 07/27/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...IWX...GRR...IND...LOT...
LAT...LON 40448579 40598638 40978710 41438793 41948832 42408822
42448756 41988510 40928484 40318528 40448579
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0800 AM CDT Mon Jul 27 2026
Valid 271300Z - 281200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
MIDWEST/LAKE MICHIGAN VICINITY...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL
HIGH PLAINS...
...SUMMARY...
Severe storms capable of strong to severe wind gusts and large hail
are expected across the Great Lakes and Midwest through tonight.
More sporadic occurrences of damaging wind are possible in the
Mid-Atlantic, Tennessee Valley, central High Plains, and southeast
Arizona.
...Midwest/Great Lakes to the Ohio/Tennessee Valleys...
A complex forecast scenario again exists today complicated by
numerous mesoscale factors and well-above-normal short-term guidance
variability. There nonetheless is an appreciable broad regional
severe potential, at least conditionally, attributable to robust or
even extreme source-region buoyancy and an appreciable belt of
northwesterly flow aloft (50+ kt at 500 mb), which could easily
support well-organized wind-producing swaths regionally into the
afternoon and tonight.
A high-moisture-content airmass is prevalent regionally to the south
of a cold front that extends across South Dakota/Minnesota toward
Lake Superior. Several corridors of storms are ongoing early this
morning, including across the western Upper Peninsula of
Michigan/far northern Wisconsin, as well as southwest lower
Michigan, with some uptick in ACCAS/mid-level convection in the
predawn hours across eastern Iowa/far southwest Wisconsin.
Increasing daytime storms, in terms of coverage/intensity/
organization, may stem from, but are not limited to, these early day
corridors. Bouts of large hail will be possible given the degree of
vertical shear/buoyancy, and some tornado risk could exist, but the
most prominent concern would be for damaging wind potential,
particularly if one or more south/southeast-moving
forward-propagating clusters emerge, which currently appear most
probable this afternoon and tonight across eastern Wisconsin/western
Michigan and Lake Michigan vicinity southeastward into Indiana,
western Ohio, and Illinois.
...Central High Plains...
Moist, post-frontal surface flow is expected across much of
Nebraska/South Dakota, shifting from northerly early in the day to
more easterly by the afternoon. Dewpoints will initially be in the
mid to upper 70s F, although strong boundary-layer mixing will
likely result in dewpoints ranging from the upper 50s/low 60s across
the Nebraska Panhandle to the low 70s across eastern Nebraska. This
reservoir of low-level moisture coupled with strong heating and
steep mid-level lapse rates will result in a corridor of moderate to
extreme buoyancy from eastern Wyoming/northeast Colorado/southwest
South Dakota eastward across south-central
South Dakota and much of Nebraska.
Most of the guidance indicates a subtle, convectively augmented
vorticity maximum will progress eastward through the northern
periphery of the Four Corner upper ridge. This should contribute to
thunderstorm development across the high terrain, which would then
progress downstream into a more moist and unstable airmass. One or
more clusters could evolve, but the overall predictability of the
convective evolution is low. That said, environmental conditions
support the potential for strong to severe gusts, including the
potential for some over 75 mph.
...Mid-Atlantic States/Delmarva...
Isolated damaging wind potential will exist during the
afternoon/evening, especially near/east of I-95 in vicinity of a
surface trough, where marginal buoyancy and deep-layer shear could
support a few stronger updrafts/downdrafts.
...Southeast Arizona...
Isolated severe-caliber wind gusts are possible over southeast
Arizona as mid-level moisture and diurnal heating leads to scattered
storms over the higher terrain. Cells are expected to move westward
into warmer temperatures and deeper boundary-layer mixing, with PWAT
over 1.25" and steep low-level lapse rates supporting strong
convective outflows.
..Guyer/Wendt.. 07/27/2026
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