397
FXUS63 KMQT 290750
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
350 AM EDT Sun Jun 29 2025

.KEY MESSAGES...

- Rain showers and thunderstorms progress eastward over Upper
  Michigan this morning. An isolated stronger storm can`t be
  ruled out near Wisconsin, however severe weather is not
  expected with this first round.

- There is a slight chance of strong to severe storms this
  afternoon and evening. Should organized storms occur, large
  hail and damaging winds will be the main severe weather
  hazards.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 349 AM EDT Sun Jun 29 2025

A broad mid level trough is noted to the WNW over the Canadian
Prairie on early morning RAP analysis with an area of upper level
diffluence over S MN and NW WI where some subtle shortwaves are also
located. This alongside the support of a modest LLJ of at least
~30kts is supporting the MCS over N WI. The remainder of tonight
weak high pressure ridging continues to depart SE toward New England
while a stationary boundary draped over W WI into central MN finally
continues its movement NE into our region. This sends lingering
convection E across N WI and into parts of the UP. Support from the
LLJ drops off as time progresses, but also there is less guidance
supporting its N extent into our CWA. Also SBCAPE gradually will
lower with time tonight as the cap strengthens. Current obs have Tds
in the mid to upper 60s over the far W and along the state line with
WI. This is supporting up to 1000j/kg SBCAPE over the far SW (~25+
j/kg of SBCIN), diminishing down to 0 j/kg by the Keweenaw and
Central UP. More widespread Tds in the 60s to 70s are noted in WI
where this system is favored to track keeping the stronger storms
outside the CWA. That said, some storms on the N end could stray
over the W half of the UP and are currently beginning to move in
over the far W. Despite moving toward unfavorable environment, bulk
shear of at least 30 kts could support the updrafts. Severe threats
of wind/hail are marginal, if that, given mid level lapse rates
struggle to maintain 6.5C/km and low level lapse rates are low. A
few hundred j/kg (<800) could help sub severe winds up to ~45 mph
mix down in stronger storms and some small hail could accompany this
as well (.5" or smaller). This environment should continue to weaken
with time diminishing threats toward sunrise. Timing has slowed,
again, with any storms just now moving in from the SW, continuing
ENE overhead through the morning hours. Shra/-tsra may clear out of
the CWA by as early as 14Z, but dry weather at the latest should
return for most by ~18Z. Otherwise, temps the remainder of tonight
stay mild in the upper 50s to 60s.

In the wake of this first round, temps warm into the mid 70s to
upper 80s as the UP is now positioned in the warm sector. Diurnal
instability climbs to 1500-2500j/kg of MUCAPE, highest S-central
where up to around 3000j/kg is possible depending on how quick this
first round is able to clear out. With ~30-35kts of deep layer
shear, DCAPE increasing to between 600-1000j/kg, low-level lapse
rates near 8C/km and mid-level lapse rates increasing to 7C/km,
organized storms would be capable of producing large hail and strong
to damaging winds. A strengthening LLJ over the E half helps support
convective development, with the area of highest probability of
strong to severe storms over the S-central. That said, confidence in
timing and more so placement remains low as CAM solutions are
spread. General consensus is for sct shra/tsra to develop in the
afternoon, continuing into this evening ahead of a cold front
approaching from the W. As this front moves through, shra/tsra
progress E and likely exit the CWA tonight. Otherwise expect another
mild night in the upper 50s to 60s.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 249 PM EDT Sat Jun 28 2025

Long term period begins Monday with mid-level troughing extending
southwest from Hudson/James Bay into the Northern Plains and Upper
Midwest. To the south, sprawling mid-upper level ridging stretching
across most of southern CONUS, with a trough slowly lifting north
along the California coastline. Ahead of the trough, ridging extends
north across the Rockies and Intermountain West into western Canada.
At the surface, a cold front looks to be draped across western or
central Upper Michigan, with showers and thunderstorms ahead of the
boundary across eastern Upper Michigan - central too if the front
ends up starting the day over the west. This front will continue
pushing eastward through the morning hours, with a secondary cold
front/slug of cold air advection pressing southeastward into the
forecast area in the afternoon/evening, coincident with the mid-
level trough axis. Its unclear how much we`ll destabilize during the
day, but if we`re able to destabilize enough, scattered showers and
thunderstorms should develop by afternoon/evening. Severe weather
isn`t expected, but if enough thunderstorm organization can occur, a
stronger storm capable of stronger winds and small hail will be
possible in the evening. Any convective activity that occurs should
diminish overnight. Expect daytime temps to climb into the mid 70s
to low 80s and lows Monday night to fall mostly in the low 60s to
mid 50s.

Mid-upper level ridging across western North America will continue
Tuesday, then begin to slowly shift eastward through the Rockies
Wednesday and Plains Thursday. This will position Upper Michigan
within northwest flow aloft and at the mercy of any shortwave riding
the ridge`s eastern flank southeastward. The first wave looks to
press into Great Lakes sometime Tuesday afternoon or night. With
surface ridging extending into the region and little destabilization
expected, shower and thunderstorm activity looks to stay north of
Upper Michigan in Ontario. The next wave looks to drop southeastward
through Ontario Wednesday or Wednesday night into Thursday morning;
while timing differences among the deterministic packages increase
with this wave, a bulk of the shower/thunderstorm activity looks to
remain focused to the north and south, where better forcing exists.
With that being said, can`t rule out at least isolated afternoon
showers/thunderstorms activity at the moment. Surface high builds in
afterwards which will linger Thursday overhead. This will work to
keep the region mostly dry.

Friday, the 4th of July, weak ridging to near zonal flow sets up
across the northern tier with multiple weak impulses embedded within
the flow. Closer to the surface, a warm front looks to stretch
across the Northern Plains or Upper Midwest.  12z guidance appears
to be trending toward precip spreading into the region from the west
by afternoon/evening, but there hasn`t been run to run consistency
about this, except by the GFS. Should this trend continue, showers
and thunderstorms may impact any evening firework plans.

Daytime temperatures Tuesday and into the weekend look largely to
span the upper 70s to low 80s while overnight temperatures fall
mostly into the 50s.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 103 AM EDT Sun Jun 29 2025

Generally VFR conditions will continue today into tonight, although
showers and storms could lower conditions to MVFR or lower at times
this morning and again late this afternoon/this evening. The light
southerly flow progressively becomes SW at IWD and SAW today and W
at CMX. No LLWS is expected across the area early this morning or
this evening, but it could be seen in some thunderstorms passing
overhead.

&&

.MARINE...
Issued at 249 PM EDT Sat Jun 28 2025

Winds will settle below 15 kts lake wide this afternoon as high
pressure continues to build into the Lower Great Lakes region.
Although winds and waves will remain mostly calm as only weaker
pressure systems affect the lake for the rest of the weekend into
next week, periodic thunderstorms may occasionally be over the lake,
bringing chances for gusty erratic winds and small hail. The best
chance for thunderstorms moves west to east late tonight into the
early morning hours of Sunday, then again following a similar
timeframe late Monday into Tuesday.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.

&&

$$

SHORT TERM...Jablonski
LONG TERM...JTP
AVIATION...TAP
MARINE...BW