textproduct: Marquette

KEY MESSAGES

- There is a roughly 20% chance of showers and thunderstorms this and tomorrow afternoon.

- Nearly normal temperatures are expected through Saturday.

- Dry weather Friday ahead of widespread rain and thunderstorm chances Saturday afternoon into Sunday. Severe weather is not expected at this time.

DISCUSSION

Issued at 355 PM EDT Wed Aug 12 2026

This afternoon, GOES Channel 2 visible imagery shows dominant NW'ly flow across the region with minimal cloud cover atop the UP. Despite the atypical status of today's insolation, with the solar eclipse and elevated wildfire smoke, temperatures are reaching into the high 70s and low 80s. Weak, sprawling surface pressure underneath fairly dry quasi-zonal flow has resulted in calm winds, nearly normal temperatures, and partly sunny skies at the surface. Some low (15- 25%) precipitation chances enter into the forecast this evening along the southeastern quadrant of the UP, and any thunderstorms that form along with this are most likely to do so along the lake breeze boundary. The HRRR and NAM both have lake breezes initiating from Lake Superior around 20Z today.

For tomorrow, a nebulous shortwave passes through the CWA while the region remains under the same synoptic pattern. CAMs are undecided on the precise manifestations, but agree that impacts will be sub- severe and mostly in the west and south of the UP. With less than 1" of PWAT available tomorrow during the second half of the day, NBM 24- hr LPMM ending at 8 pm Aug 13 (Thurs) shows only 0.02 - 0.16 inches of accumulation. Otherwise, with surface high pressure building in, temperatures are expected to remain very close to normal for the next few days.

The next big chances for precipitation arrive Saturday afternoon as this week's ridging exits east and a surface trough drapes down across the region from Ontario. Starting with rainfall, WPC has the entire state of MI in a Day 4 Marginal Risk of the ERO. The EPS has PWAT > 1.5" 18Z Saturday through 18Z Sunday, with greatest PWAT near 2" south near Menominee County; the CMCE has only 1 - 1.5" during this time. The NBM has widespread 10-20% chance of rainfall greater than 0.5", and the 90th percentiles of 24-hour accumulation distributions ranges from just over 0.5" to upwards of 1" with the highest accumulations being in the southern UP. Along with elevated moisture, surface moisture appears impressive: dewpoints look to climb into the 60s across the UP and into the high 60s near Menominee Co. Saturday evening, and remain high through Sunday. Correspondingly, mean NBM SBCAPE maxes out in that same area around 500 J/kg. Though severe weather is not expected at this time, details may change as the event moves closer.

Looking further out, LREF 500 mb heights clusters start to show discrepancies at the CONUS level on Day 6 (Aug 17-18) with timing and behavior of Pacific trough moving onshore. These differences start to be felt in Upper Midwest on Day 7 with respect to how quickly this late week/weekend's ridging exits our area, and inject uncertainty into the pattern and thus precipitation chances in the Day 6-7 timeframe.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 149 PM EDT Wed Aug 12 2026

VFR conditions expected to prevail across Upper Michigan through the period in benign northwest flow pattern aloft. A few of the hi-res models continue to depict isolated to scattered showers and thunderstorms popping up along the lake breeze in the vicinity of KSAW this afternoon, the possibility of which is supported by a deepening cumulus field evident over the central UP on visible satellite as of 18z Wed. That being the case, will continue to carry a PROB30 through 21z. Chances for patchy fog development tonight remain around 15%, so will will continue to leave that out of the TAFs for this cycle. Some models depict a few showers from weakening upstream convection over MN surviving into the western UP Thu morning, prompting PROB30s for KIWD after 12z Thu and for KSAW closer to 18z Thu.

MARINE

Issued at 355 PM EDT Wed Aug 12 2026

For Lake Superior, calm conditions remain until Friday morning. As the pressure gradient tightens for a short time in the wake of due to mid-level shortwave passing through on Friday evening, increased NE'ly flow with funneling near the west end of the lake causes gusts to 25 knots. Conditions go calm again until Saturday afternoon when southerly flow picks up prior to a surface low/cold front passing through. This system brings with it chances of (30-60%) precipitation and thunder (10-20%). As the center of low is predicted to pass very nearly over Lake Superior, slight changes in the placement and timing of this track could drastically change wind direction. At this time, gusts over the open lake look to top out near 20 knots in the western and central lake between Saturday afternoon, and near 25 knots Saturday evening through Sunday evening in the eastern open lake and nearshore zones. The highest wind speeds will be felt as NW'ly flow after frontal passage on Sunday due to a relatively tight pressure gradient between the outgoing sfc low and incoming sfc ridging on its heels. After this point, calm conditions are anticipated on Lake Superior through till Monday evening, when a surface trough makes its way toward the region, causing SW'ly flow to pick up. As winds veer to westerly and the trough passes to our north, the lake could see periods of gusts to 15 knots.

For the Bay of Green Bay and northern Lake Michigan, calm conditions (gusts <10 knots) are expected through until Saturday morning. As SE'ly flow picks up ahead of the front on Saturday, gusts increase to 15 knots for short period in the afternoon and evening. Calm conditions are expected to redevelop for most of Sunday until the evening, when northerlies behind the front bring gusts to 20 knots Sunday evening. Calm conditions through till Tuesday.

MQT WATCHES/WARNINGS/ADVISORIES

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