RSS Mesoscale Discussions from Storm Prediction Center
WW 505 SEVERE TSTM MI LH LM LS 202350Z - 210600Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 505
NWS Storm Prediction Center Norman OK
750 PM EDT Mon Jul 20 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Northern Lower Michigan
Lake Huron
Lake Michigan
Lake Superior
* Effective this Monday night and Tuesday morning from 750 PM
until 200 AM EDT.
* Primary threats include...
Scattered damaging wind gusts to 70 mph possible
Isolated very large hail events to 2 inches in diameter possible
A tornado or two possible
SUMMARY...Widely scattered intense storms over Upper Michigan and
northern Wisconsin will track southeastward into the watch area this
evening, posing a risk of damaging winds and hail. A tornado or two
is possible.
The severe thunderstorm watch area is approximately along and 55
statute miles east and west of a line from 15 miles southeast of
Manistee MI to 40 miles north northeast of Pellston MI. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU5).
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 500...WW 501...WW 504...
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
28030.
...Hart
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WW 0505 Status Updates
STATUS REPORT ON WW 505
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 50 WNW TVC
TO 25 NE TVC TO 25 WNW APN.
..MEAD..07/21/26
ATTN...WFO...APX...GRR...
STATUS REPORT FOR WS 505
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
MIC009-019-035-039-055-079-085-089-101-105-113-119-133-137-165-
210540-
MI
. MICHIGAN COUNTIES INCLUDED ARE
ANTRIM BENZIE CLARE
CRAWFORD GRAND TRAVERSE KALKASKA
LAKE LEELANAU MANISTEE
MASON MISSAUKEE MONTMORENCY
OSCEOLA OTSEGO WEXFORD
LMZ323-344-345-346-364-366-849-868-210540-
CW
. ADJACENT COASTAL WATERS INCLUDED ARE
GRAND TRAVERSE BAY SOUTH OF A LINE GRAND TRAVERSE LIGHT TO
NORWOOD MI
SLEEPING BEAR POINT TO GRAND TRAVERSE LIGHT MI
POINT BETSIE TO SLEEPING BEAR POINT MI
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WW 0504 Status Updates
STATUS REPORT ON WW 504
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 30 WNW BRL
TO 45 WSW PIA TO 5 SW SPI.
..MEAD..07/21/26
ATTN...WFO...DVN...ILX...
STATUS REPORT FOR WS 504
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
ILC017-067-109-129-137-167-169-171-210340-
IL
. ILLINOIS COUNTIES INCLUDED ARE
CASS HANCOCK MCDONOUGH
MENARD MORGAN SANGAMON
SCHUYLER SCOTT
MOC045-199-210340-
MO
. MISSOURI COUNTIES INCLUDED ARE
CLARK SCOTLAND
THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE
REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL
INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES
CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES.
Read more
WW 0501 Status Updates
STATUS REPORT ON WW 501
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 35 ENE VOK
TO 45 NNW GRB TO 10 SSE ESC.
..MEAD..07/21/26
ATTN...WFO...MQT...GRB...
STATUS REPORT FOR WT 501
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
WIC009-015-029-061-071-083-087-115-135-137-139-210340-
WI
. WISCONSIN COUNTIES INCLUDED ARE
BROWN CALUMET DOOR
KEWAUNEE MANITOWOC OCONTO
OUTAGAMIE SHAWANO WAUPACA
WAUSHARA WINNEBAGO
LMZ221-248-250-521-522-541-542-543-210340-
CW
. ADJACENT COASTAL WATERS INCLUDED ARE
GREEN BAY NORTH OF LINE FROM CEDAR RIVER MI TO ROCK ISLAND
PASSAGE
SEUL CHOIX POINT TO POINT DETOUR MI
5NM EAST OF A LINE FROM FAIRPORT MI TO ROCK ISLAND PASSAGE
GREEN BAY SOUTH OF LINE FROM CEDAR RIVER TO ROCK ISLAND PASSAGE
Read more
WW 0500 Status Updates
STATUS REPORT ON WW 500
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 45 E DNS TO
20 N OXV TO 25 ENE OTM.
WW 500 WILL BE ALLOWED TO EXPIRE AT 210300Z.
..MEAD..07/21/26
ATTN...WFO...DMX...ARX...DVN...
STATUS REPORT FOR WT 500
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
IAC001-007-049-051-073-077-087-101-107-111-117-121-123-125-135-
153-177-179-181-185-210300-
IA
. IOWA COUNTIES INCLUDED ARE
ADAIR APPANOOSE DALLAS
DAVIS GREENE GUTHRIE
HENRY JEFFERSON KEOKUK
LEE LUCAS MADISON
MAHASKA MARION MONROE
POLK VAN BUREN WAPELLO
WARREN WAYNE
THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE
REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL
INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES
CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES.
Read more
No Mesoscale Discussions are in effect as of Tue Jul 21 05:53:03 UTC 2026.
SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0800 PM CDT Mon Jul 20 2026
Valid 210100Z - 211200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE UPPER GREAT LAKES INTO THE LOWER MISSOURI VALLEY...
...SUMMARY...
Severe thunderstorms capable of producing damaging wind gusts,
severe hail, and a couple of tornadoes will continue across portions
of the Upper Great Lakes and Lower Missouri Valley through late
tonight.
...01Z Update...
Water-vapor imagery and VWP data indicate a robust midlevel wave and
accompanying belt of 50-60-kt west-northwesterly flow overspreading
the Upper Midwest, and this feature will continue east-southeastward
across the Great Lakes region tonight. In the low-levels, an
attendant cold front will continue east-southeastward across this
region as well. In the Upper Great Lakes and Midwest, 50-60 kt of
deep-layer shear (sampled by regional VWPs) oriented perpendicular
to the cold front and a relatively narrow corridor of strong
pre-frontal buoyancy (around 3000 J/kg MLCAPE) will continue to
promote semi-discrete supercell structures. Locally damaging wind
gusts, severe hail, and a couple of tornadoes will be possible with
this activity, given ample low-level hodograph curvature (around 250
m2/s2 effective SRH) beneath the core of a 40-kt LLJ. This activity
will generally spread east-southeastward across parts of Lower MI
tonight, where a continued risk of damaging wind gusts, severe hail,
and a tornado or two will continue ahead of the cold front before
encountering increasingly stable air.
Farther south, a couple organized clusters are tracking southward
across parts of southern IA and western IL. Given strong cold pools
with this activity, the primary concern will be severe wind gusts
and isolated/sporadic hail. These storms will continue tracking
south-southeastward along a surface-based buoyancy gradient before
gradually weakening overnight.
..Weinman.. 07/21/2026
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SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1245 AM CDT Tue Jul 21 2026
Valid 211200Z - 221200Z
...Synopsis...
...Northern California and west/central Oregon...
Along the northwestern periphery of a large-scale ridge encompassing
much of the central and western CONUS, ample mid-level moisture will
be in place atop a warm and dry airmass across parts of northern CA
into OR. Forecast soundings depict inverted-V profiles with weak
(albeit sufficient) buoyancy for high-based thunderstorms across the
area during the afternoon and evening hours. Cloud cover, smoke, and
warmer temperatures aloft will help limit thunderstorm
development/coverage across the IsoDryT area, but isolated
thunderstorms remain possible. While 0.8 to 1.2 inch PWATs may
promote a mix of wet/dry storms, relatively fast storm motions and
the dry boundary layer should limit precipitation efficiency. As a
result, isolated lightning-induced ignitions will be possible within
a very dry fuelscape.
...South Carolina...
Progressive upper-level troughing will continue across the
northeastern U.S. as a closed low traverses northern Ontario,
sending a cold front through the Ohio Valley. Enhanced 850 mb
southwesterly flow ahead of the front will encourage gusty surface
winds amid minimum RH values of 30-40% in portions of South
Carolina. Locally elevated fire weather conditions are likely, as
ERCs generally range from the 80th-95th percentile across this area.
..Elizalde-Garcia.. 07/21/2026
...Please see www.spc.noaa.gov/fire for graphic product...
Read more
SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1250 AM CDT Tue Jul 21 2026
Valid 221200Z - 231200Z
...Synopsis...
Upper-level troughing will remain in place across the eastern U.S.
as a southward progressing cold front promotes widespread chances of
rainfall along the Eastern Seaboard on Day 2/Wednesday. Meanwhile,
the remnants of Post-Tropical Cyclone Elida will continue to
translate northward along the western periphery of a large-scale
ridge across the western CONUS. As high pressure shifts towards the
Four Corners, additional monsoonal moisture will advect into the
Pacific Northwest.
Despite being less than 48 hours from the forecast period, model
data (including high-resolution guidance) exhibits prominent
differences in the amplitude of the upper ridge; thus, disparity in
the strength and direction of upper/mid-level flow. While a mix of
wet/dry thunderstorms are still expected across the IsoDryT area, a
slightly more eastward progression of the Pacific upper low could
result in expasive thunderstorm coverage. Forecast PWAT values do
approach 0.9-1.25", but 20-30 kt storm motions should inhibit
precipitation efficiency, resulting in greater potential for
lightning ignitions. Given very receptive fuels and fire activity in
the area, a subsequent outlook upgrade to a Scattered Dry
Thunderstorm area may be warranted if the wetting rain footprint
remains relatively smaller to thunderstorm coverage.
..Elizalde-Garcia.. 07/21/2026
...Please see www.spc.noaa.gov/fire for graphic product...
Read more
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