Severe Thunderstorm Warning 21, NWS Marquette, MI

862 
WWUS53 KMQT 122005
SVSMQT

Severe Weather Statement
National Weather Service Marquette MI
405 PM EDT Sun Jul 12 2026

MIC103-122030-
/O.CON.KMQT.SV.W.0021.000000T0000Z-260712T2030Z/
Marquette MI-
405 PM EDT Sun Jul 12 2026

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 430 PM EDT
FOR CENTRAL MARQUETTE COUNTY...

At 404 PM EDT, a severe thunderstorm was located over Negaunee, or
near Ishpeming, moving southeast at 30 mph.

HAZARD...Quarter size hail.

SOURCE...Radar indicated.

IMPACT...Damage to vehicles is expected.

Locations impacted include...
Marquette, Ishpeming, Presque Isle, Negaunee, Little Presque Isle,
West Ishpeming, Trowbridge Park, Harvey, Palmer, National Mine, and
Sugarloaf Mountain.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4657 8777 4667 8751 4653 8727 4638 8765
      4656 8776
TIME...MOT...LOC 2004Z 333DEG 28KT 4654 8760 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...<50 MPH

$$

Jablonski

Area Forecast Discussion
National Weather Service Marquette MI
219 PM EDT Sun Jul 12 2026

.KEY MESSAGES...

- The warmest airmass of the season so far will impact the UP
  with highs in the 90s today through Tuesday. High dewpoints
  and poor overnight recoveries will increase cumulative
  impacts. People sensitive to heat should make preparations for
  these conditions.

- There is a chance of thunderstorms today with the warm and
  unstable airmass. The SPC has outlooked a Marginal Risk
  (category 1 of 5) for severe thunderstorms (5-15% chance).

&&

.UPDATE...
Issued at 325 AM EDT Sun Jul 12 2026

The going forecast remains mostly on track this morning. GOES-East
Nighttime Microphysics RGB imagery shows mostly clear skies over the
UP, with some thunderstorms over northern Ontario that so far are
tracking to miss the region to the north. The two big forecast
impacts for the day are the potential for severe thunderstorms and
the oppressive heat, with the heat lasting through at least
Tuesday.

Today's Thunderstorms: CAMs continue to be highly spread on the
details of timing and storm mode for thunderstorms today. The
ingredients are a mixed bag: shear is ok with HREF mean 0-3km SRH of
around 250 by 18Z and good curvature in the low levels of the
hodograph, though speed shear is somewhat lacking. Lift is
questionable at best given approaching synoptic ridging and surface
high pressure providing subsidence, but with significant heating
today, some places may reach the convective temperature and while
thermodynamically speaking, a lake breeze should be possible,
southwest winds of around 10 kt may prevent the lake breeze from
penetrating inland and serving as a mesoscale frontal lifting
mechanism. Lift over the UP may not even be necessary as CAMs show a
variety of possible MCS initiation scenarios over northwest
Ontario/MN Arrowhead. Instability and moisture will be abundant as
surface Tds look to be around the 70 degree mark and PWATs in excess
of 1.5 inches this afternoon are over the 90th percentile of
climatology, per HREF. The moisture and excessive heat will allow
significant destabilization especially in the west half, where the
HREF mean SBCAPE balloons to locally over 3,000 (!) J/kg. All
this to say, the ingredients will generally be present for
severe thunderstorms but an actual lifting mechanism to initiate
convection is nebulous at best and lacking at worst. This is a
high ceiling, low floor forecast scenario because if
thunderstorms form, all severe threats are possible, but there
is also a scenario where little to no convection actually occurs
(or passes to our north or south). The SPC Outlook remains at a
Marginal Risk (category 1 of 5) of severe thunderstorms.

Today's Heat: A Heat Advisory is in effect for the western half of
the UP as the warming trend from the last few days continues. The
aforementioned dew points near 70 will combine with highs in the 90s
for most to give a 3+ hour window this afternoon of locally triple-
digit heat indices. The east will miss out on the hottest
temperatures today as the aforementioned southwesterly surface flow
will advect in Lake Michigan-cooled air. That southwest surface flow
will also make for downsloping to even further heat up the
shorelines of Marquette and Baraga Counties as well as portions of
the far west that downslope from the highlands along the MI/WI state
line.

Monday/Tuesday Heat: The heat comes to a head Monday and Tuesday as
the upper level ridge extends overhead from the west. Multiple
weather balloon sites with periods of record dating back to the
middle of the 20th century and 50,000+ launches will be in danger of
breaking their all-time 500mb height record, potentially multiple
times. As 1000-500mb thickness is proportional to temperature, a
record 500mb height would mean record high temperature records are
also in play. Monday, the usually cool-biased LREF shows up to 30-
60% chances of exceeding 100 degrees in some interior locations
while the NBM (which can be warm biased) shows widespread 50-90%
chances of exceeding 100 degrees. These probabilities are similar
(maybe slightly lower and shifted east somewhat) Tuesday. These
temperatures combined with dew points in the 60s to low 70s will
also lead to heat indices climbing into the triple digits for
most. Making matters worse is that the LREF shows that the west
half may be 20% or less likely to fall below 70 degrees
overnight for both Monday and Tuesday mornings. Without air
conditioning, vulnerable populations (such as the elderly and
immunocompromised, outdoor workers, and outdoor recreationists,
among many others) are going to struggle not only to battle the
daytime heat, but also may not get relief overnight. Thus, the
Heat Advisory may be extended into the overnight hours and into
the next day. Alternatively, the NBM does have some isolated
downsloping areas in the west half and much of the Lake Michigan
shores exceeding 105 heat index Monday, so an Excessive Heat
Watch may also be warranted.

Midweek and beyond: Differences in how ensembles handle the troughs
that bookend the ridge result in significant spread from Wednesday
onwards, with LREF 10th to 90th percentile spread of at least 10-15
degrees (the difference between highs cooling to the upper 70s or
low 90s heat lingering). Thus, did not deviate from the NBM in that
time period.

&&

.DISCUSSION...
Issued at 408 PM EDT Sat Jul 11 2026
Amended at 325 AM EDT Sun Jul 12 2026

Over the next few days, the robust Four Corners high amplifies and
shifts northeast toward the Upper Great Plains. As the high
approaches the Upper Great Lakes on Monday, its northward progress
is deflected eastward as a sub-arctic trough over the Hudson Bay
deepens and an upper-level jet streak moves over the Canadian
Prairies. Thus, continued anticyclonic flow advects extremely
anomalously warm air toward the region for several days before
steering flow shifts it south. The NAEFS ESAT is currently showing
500 hPa mean geopotential height at 100% of climatology for most of
the UP for Monday afternoon through late Tuesday.

For today's ramp-up period to this extreme heat, a Heat
Advisory has been issued for noon through 9PM for the western UP
given widespread apparent temperatures (heat indices) reaching
90F-100F. The NBM has over 50% probability of high temps greater
than 90F for nearly all of the CWA, with the exception of south
shore of eastern UP whose high temps will be influenced by
light, onshore southerly flow off Lake Michigan. Portions of far
western UP and Keweenaw have highest NBM probabilities of over
90% chances of greater than 90F, and over 50% chance of greater
than 95F. NBM MaxT interdecile spread for today tops out at 9F,
which puts most of UP in the mid-80s at the low end.
Southwesterly surface flow indicates extra warming is possible
via downsloping for the central UP coast, from Copper Harbor to
western Alger County. With NBM mean dewpoints in the mid to high
60s for the second half of today through Monday morning, this
puts apparent temperature on the first day of this heat streak
at 90F-100F for the western UP, and in the upper 80s in the
eastern UP.

Along with the warm, moist airmass, thunderstorm potential is
nonzero for this afternoon. HREF mean SBCAPE ranges from
1500-3000 J/kg tomorrow evening, concentrated in the western UP
and including the Keweenaw. HREF bulk shear magnitude values
increase to moderate through the day as the jet moves in from
the NNW, though directional shear (from HRRR soundings) is
largely unidirectional, veering from NW'ly to N'ly through the
night, above the low-levels. With scant synoptic forcing and
high pressure moving in, any lake breezes which form may be a
focus for convection. Though CAMs struggle to arrive at
consensus with respect to time and placement, the environment is
supportive of isolated severe storms; thus, SPC's Marginal Risk
for severe thunderstorms tomorrow.

This evening has poor recoveries from the heat with apparent
temps only decreasing down to the high 60s and low 70s by early
Monday morning. Should widespread thunderstorms manifest this
afternoon and evening, cloud cover and recent rainfall may
increase mugginess. With recent NBM runs trending overnight
minimum temperatures higher with the latest model runs, this may
worsen cumulative heat-related impacts.

The UP is set to experience widespread apparent temperatures in the
high 90s and triple digits on Monday and Tuesday, the worst of which
will be felt between 1PM and 8PM each day. Between MinT's decreasing
only to the low 70s and dewpoints in the high 60s, Monday's
overnight period recovers particularly poorly with apparent temps in
the mid 70s. As the mid-level ridge begins to flatten out toward
midweek, the warmest airmass shifts south of the CWA, though it's
possible that above-average heat will remain through the week. The
NBM shows widespread, significant interdecile spread (>15F) for
temperatures after Wednesday night.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 218 PM EDT Sun Jul 12 2026

VFR flight conditions are expected through the duration of the 18Z
TAF period. The one exception to this is patchy BR yielding MVFR/IFR
vis at CMX early Monday morning, but confidence was too low to
include at this time (<30% chance). Also, there is around a 30%
chance for TSRA to impact SAW this afternoon. Otherwise southwest to
west winds remain elevated around 10-15 kts, strongest at CMX where
gusts up to 25 kts are expected. There also is a LLWS threat at SAW
late tonight.

&&

.MARINE...
Issued at 408 PM EDT Sat Jul 11 2026
Amended at 325 AM EDT Sun Jul 12 2026

There will be an uptick in winds starting today as the pressure
gradient tightens while a strong low moves along the high
pressure ridge. Southwesterly winds will increase to 15-20 kt on
today and to 25-30 kt over the central portions of the lake by
Monday, persisting through the first half of next week and
expanding to include western and eastern portions of the lake as
well. Models continue to trend toward a few gale force gusts
late Monday into Tuesday across the central portions of the
lake.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for
     MIZ001>005-009>011-084.

Lake Superior...
None.
Lake Michigan...
None.

&&

UPDATE...GS
DISCUSSION...RE/GS
AVIATION...77
MARINE...TDUD/GS

Preliminary Local Storm Report
National Weather Service Marquette MI
1149 AM EDT Sun Jul 12 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1138 AM     Hail             2 E Three Lakes         46.55N 88.17W
07/12/2026  M0.88 Inch       Baraga             MI   Trained Spotter

            Observer noted a quick burst of small hail
            ranging from pea to nickel size.

&&

77

Preliminary Local Storm Report
National Weather Service Marquette MI
1230 PM EDT Sun Jul 12 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1224 PM     Hail             Herman                  46.66N 88.37W
07/12/2026  M1.75 Inch       Baraga             MI   CO-OP Observer

            Observed ping pong to golf ball sized hail.

&&

77