983
FXUS63 KMQT 052330
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
730 PM EDT Tue Aug 5 2025

.KEY MESSAGES...

- Smoke from Canadian wildfires will continue impacting air
  quality and may locally reduce visibility at times. An Air
  Quality Advisory remains in effect for all of Upper Michigan
  through Wedensday.

- Episodic showers and thunderstorms will be possible again
  Wednesday night through the weekend.

- Heat and humidity increase late this week into the weekend,
  with a 40-70% chance of heat indices exceeding 90 degrees
  Friday and Saturday over most areas and 90%+ chance for areas
  in the lower elevations near Lake Superior.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 346 PM EDT Tue Aug 5 2025

This afternoon water vapor imagery and model 500mb heights showed
the rex block like pattern continuing to break down. The upper level
high had moved east into Northern Ontario and the upper level low
over the Northern Plains was opening up. Weak shortwaves continued
to bring enought lift into the area to result in mid and high level
cloudiness along with elevated radar echoes, most of this
precipitation was evaporating before reaching the ground.  However,
a few showers and thunderstorms had formed in the vicinity of the
Lake Superior and Lake Michigan lake breeze boundaries where RAP
analysis showed around 1000 J/kg MLCAPE.

Air quality issues continued today with widespread smoke and haze
over all of the Great Lakes and extending all the way to the coast
of New England. A surface high pressure over Quebec was helping to
transport this smoke back to the west and north into the U.P.
Reductions in visiblity were being reported at the ASOS/AWOS
stations. As this high pressure finally begins a slow trek to the
east we will hopefully see the smoke moving out of the area late
Wednesday.

There is still the threat for showers and a few thunderstorms this
afternoon. Ensemble mean SBCAPE of 800-1200 J/kg are forecast over
the central U.P with lesser instability in the far east and west. A
weak shortwave passing though could help trigger isolated showers
and thunderstorms during peak heating, especially near the lake
breeze boundaries. Shear is weak, less than 15kts, so not expecting
any long lasting, organized convection. Showers and thunderstorms
will diminish quickly later this evening with the loss of heating.

On Wednesday the upper level high pressure will shift well to the
east and flattern as troughing moves into the Pacific NW and the
high pressure ridge over the southwestern U.S expands and shifts
easteward. This will be the start of a more active pattern and a few
showers or thunderstorms could approach the far west late in the
afternoon as the first of several shortwaves approaches the area.

Temperatures tonight will be similar to last night, 50s inland to
the low 60s near the lakeshores. Highs on Wednesday will be a few
degrees warmer than today, reaching the low 80s, with mid 80s in the
southerly downslope areas near Lake Superior.

&&

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
Issued at 346 PM EDT Tue Aug 5 2025

An active pattern will be in place from Wednesday night trough
early next week. Multiple shortwaves will impact the area bringing
episodes increased chances for showers and thunderstorms. The first
shortwave will move into the area on Wednesday night with the best
chance for showers and thunderstorms in the west, shifting to the
central U.P on Thursday. Ample moisture will be transported into the
region as a strong southerly low level jet sets up. PWATs could
approach 1.5" on Wednesday night and Thursday. There is the threat
for heavy rain with any thunderstorms that form. WPC has a marginal
risk (5%) for excessive rainfall in the western U.P on Wednesday
night.

We may get a reprieve from precipitation chances during the day
Friday but a hot and muggy airmass could make outdoor activities
a bit uncomfortable through Saturday. At this point it doesn`t
look like Lake Superior will provide much in the way of cooling
effects with southerly winds and little chance for a lake
breeze. With the southerly flow the NBM probabilities for 90F+
temperatures on Fri and Sat are highest (>90%) in the lower
elevations near Lake Superior. Deterministic guidance is in the
low 90s for highs in this area with upper 80s to near 90 over
the interior. These temperatures combined with dewpoints near
70F will bring heat indices to the low to mid 90s both days.
Those planning outdoor activities should take precaution to have
a way to cool off and stay hydrated.

Temperatures cool off some for Sunday into Monday with the west
seeing dewpoints falling back to the low 60s. Showers and
thunderstorm chances increase for Friday night through Monday.

The axis of greatest instability through Friday looks to remain west
of the area, over the Northern Plains and MN on Thursday and Friday.
Ensembles are showing mean MUCAPE of 2500 J/Kg over much of the
central and western U.P. for Thursday and into at least Saturday.
Shear looks to be the limiting factor for severe convection,
generally less than 25kts with the higher shear remaining west of
the area. That being said with uncertainty in timing and placement
of shortwaves and evolution of convective complexes it definitely
bears watching.

Heavy rain will also be a concern for the weekend and WPC has put
most of the western and central U.P in a marginal risk (5%) for
excessive rainfall on Saturday, PWATs will be near or over 1.5".

On Sunday and Monday the threat for showers and thunderstorm will
shift more towards the central and eastern U.P as the storm track
and deeper moisture shifts a bit to the south and east.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 730 PM EDT Tue Aug 5 2025

VFR conditions are expected during the 0Z TAF period at IWD and CMX,
while periods of MVFR vis is expected at SAW. Canadian wildfire
smoke still residing in the region will impact all sites through Wed
as it lifts N over the UP again, but slow improvement is anticipated
on Wed; the only site expected to reach MVFR from this is SAW. This
HZ could be joined by patchy MVFR BR/FG as well at SAW tonight.
Otherwise expect SE to E winds on Wed to around 10 kts.

&&

.MARINE...
Issued at 346 PM EDT Tue Aug 5 2025

Winds will remain light, below 20 knots, through the next few days.
More active weather will develop and continue into the weekend, with
showers and thunderstorms returning to the forecast starting
Wednesday night. Model guidance suggests winds remain below 20 knots
for late week but wouldn`t be surprised to see winds ramp up a bit,
to 25 knots late this week as southerly flow increases, especially
on Saturday.

&&

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

&&

$$

SHORT TERM...NL
LONG TERM...NL
AVIATION...Jablonski
MARINE...NL