560
FXUS63 KMQT 201856
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
256 PM EDT Mon Jul 20 2026

.KEY MESSAGES...

- Smoke from upstream wildfires will continue to impact Upper
Michigan. Air Quality Alerts remain in effect today trough midnight
tonight. Consider limiting strenuous outdoor activity or remaining
indoors when possible.

- Strong to severe thunderstorms capable of producing damaging winds
and large hail are anticipated this afternoon and evening. Those
with outdoor plans should continue to monitor forecast updates.

- The Storm Prediction Center has maintained a Slight Risk (level 2
of 5) for severe weather across the entire UP today with an Enhanced
Risk (level 3 of 5) extending into much of the west-central.

- Cooler and breezy conditions arrive on Tuesday. Gales are expected
over Lake Superior along and east of the Keweenaw Tuesday morning
through the evening. This will also result in dangerous swim
conditions for the Lake Superior beaches.

&&

.DISCUSSION...
Issued at 256 PM EDT Mon Jul 20 2026

Strong thunderstorms marched across the northern portions of the
U.P. this morning bringing marginally severe hail and isolated
strong winds gusts. A possible wake low had developed behind the
thunderstorms bringing strong winds over Lake Superior, particularly
in the Grand Marais area where gusts reached 60 mph. Visible
satellite had showed clearing skies over the central and western
U.P. with the exceptions of a weakening line of showers and
thunderstorms east of the Keweenaw. This has allowed the western
part of the U.P. to warm well into the 80s with dewpoints in the
upper 60s to low 70s, making it feel muggy. Surface pressure
analysis showed low pressure moving across southern Ontario with the
associated surface trough extending south into northern MN and the
central Plains. At the upper levels a well defined shortwave was
evident over southern Ontario with a strong jet rounding the base of
the trough. Southwest flow at the surface was helping to advect the
smoke out of the area with likely continued improvement through the
day and tonight.

Low pressure over southern Ontario will move east to near James Bay
by Tuesday morning, dragging a cold front across the U.P. Ahead of
the front the atmosphere will continue to become more favorable for
thunderstorms, some of them strong to severe. WOFS shows mlcape 1500-
2500 J/kg along with 45-50kt of deep layer shear. While a cap
remains in place, with most of the ongoing convection of Lake
Superior owing to large scale ascent, the cap will weaken through
the afternoon. Any storms that develop this afternoon could be
discrete supercells with all thunderstorm hazards on the table. The
latest WOFS run shows distinct helicity tracks across the central
U.P. indicative of discrete supercells. There is a non-zero tornado
threat, especially over the central U.P. where hodographs are deeply
curved and 0-1 SRH could reach or exceeds 300 m^2/s^2. However, the
main threats will be large hail (potentially 2" or greater) and
strong damaging winds (potentially as high as 80mph). As the front
moves into the area this evening could see the storms build upscale
into a linear system. If this happens the storms will transition to
mainly a wind threat has they move east from the central U.P.
through the eastern U.P. There is still uncertainty as to the
coverage of thunderstorms. Please continue to monitor the forecast
and have a way to receive severe weather warnings.

The main hazard is expected this afternoon into the evening as a
fairly volatile atmosphere for our neck of the woods shapes up. As
strong synoptic support spreads over the area and airmass recover
takes place, CAM ensembles suggest MUCAPE values climbing near 2500
j/kg. What is most impressive is the kinematic environment. Strong
mid-level flow will increase bulk shear between 45-55 kts and sickle
shaped low-level hodographs support 0-1 km SRH upwards of 100-200
m2/s2 (150-250 1-3km SRH). As storm coverage increase ahead of and
along a surface cold front, all severe weather hazards are on the
table, including tornadoes should isolated supercells be maintained.
Steep lapse rates aloft will contribute to a sizable hail threat in
supercells, potentially 2" or greater. Once storms grow upscale into
a more linear segment, damaging winds will then become the main
threat. SPC has maintained a Slight Risk (level 2 of 5) for the
entire UP with an area of the west and central UP in an Enhanced
Risk (level 3 of 5) for severe weather. All of this is to say that
if you have outdoor plans today, especially in the afternoon and
evening, have a way to receive a warning and a plan should one be
issued.

Expect cooler conditions on Tuesday into Wednesday behind the cold
front that will sweep through the area tonight. High temperatures
will be mainly in the 70s with 60s possible close to Lake Superior.
It will be breezy on Tuesday with north winds potentially gusting to
30 mph over the land areas and over 45 mph over the Great Lakes.
Some lingering showers are likely for the NW wind "snowbelts" and
upslope favored areas on Tuesday as 850 mb temps cool between 5-10C.
This may aid in lake-enhanced showers as the nearshores and areas of
the west and central lake have warmed between 15-20C. Swim
conditions will become dangerous on Tuesday for the Lake Superior
beaches of Marquette and Alger County.

The area remains under northwest flow aloft into the early part of
the weekend with a ridge building back over the central U.S. This
will bring the opportunity for showers and thunderstorms as weak
disturbances in the flow push across the U.P. Afternoon temperatures
will be seasonable, upper 70s to low 80s, with lows in the 50s.
Temperatures will warm to the mid 80s on Sunday as the ridge shifts
east over the Upper Great Lakes.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 200 PM EDT Mon Jul 20 2026

Radar imagery as of 18z depicts the latest round of showers and
thunderstorms clearing the Keweenaw and pushing into central Lake
Superior. Expect some lingering stratus to produce MVFR cigs at
KCMX through about 19z. Otherwise, mainly VFR over most of the rest
of the UP for now as this morning`s activity exits to the east,
though still currently seeing some smoke and locally reduced
visibilities to around 3 miles in the KSAW observations. The next
round of showers and thunderstorms will develop over the western and
central UP later this afternoon and push east through the evening,
warranting PROB30 for TSRA at all sites after 21z. Some of
these storms could be strong to severe as clearing skies help to
build instability back up in the near term. All modes of severe
will be possible, with large hail and damaging winds gusts
possible at the terminals. Severe threat will diminish after
01-02z as activity exits to the east, yielding VFR conditions
through most of tonight. Expect another batch of showers to
develop 09-12z Tuesday morning, accompanied by MVFR cigs at all
sites into the end of the TAF period.

&&

.MARINE...
Issued at 256 PM EDT Mon Jul 20 2026

It will be breezy across the lake through this evening with
southwest winds of 20-30kt expected. A few rounds of thunderstorms
are expected through the evening as a deep low pressure moves
through Ontario and a cold front approaches the lake. Some of the
thunderstorms could be severe with large hail and high winds this
afternoon and evening.

Late tonight the thunderstorms threat will diminish and winds will
shift northwesterly as the cold front pushes through the area.
Strong pressure rises behind the front of 6-8 mb/6hr will result in
strengthening winds. Gales are expected for most of the lake along
and east of the Keweenaw on Tuesday, as high as 40kt. Over the west
expect winds in the 20-30kt range.

Winds fall below 20kt over the west for Wednesday with 20-30kt
Northwest winds continuing over the east, before settling down below
20kt late Wednesday night as the flow turns back to the southwest.
Southwest winds will continue through Saturday, mainly between 15
and 25kt.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Beach Hazards Statement until 10 PM EDT this evening for
     MIZ014.

Lake Superior...
  Gale Watch from Tuesday morning through late Tuesday night for
     LSZ244>251-265>267.

Lake Michigan...
None.

&&

$$

DISCUSSION...BW/NL
AVIATION...CB
MARINE...NL