textproduct: Marquette

KEY MESSAGES

- Low humidity paired with gusty winds and warm temperatures this afternoon will lead to elevated to critical fire weather conditions into this evening. Red Flag Warnings remain in effect for most of the U.P. through 9 PM EDT/8 PM CDT.

- Warmer than normal temperatures continue through early next week.

- Multiple rounds of heavier rain showers and strong to potentially severe thunderstorms expected Sunday night through Tuesday.

DISCUSSION

Issued at 355 PM EDT Sat May 16 2026

Visible satellite imagery shows clear skies across Upper Michigan and Lake Superior this afternoon. RAP analysis depicts fairly zonal flow aloft over the Upper Great Lakes, with a subtle upstream ridge over the Northern Plains/Canadian Prairie and a trough moving onshore over the Pacific Northwest. Temperatures reside in the 70s across much of the U.P. and even the low 80s near the WI border as of mid afternoon. Dry adiabatic lapse rates depicted by model soundings and latest SPC mesoanalysis are promoting deep mixing which has allowed minimum humidity values to fall into the 20s across much of the area and as low as the mid teens across south-central per latest surface observations. Meanwhile, surface high pressure building over northwest Ontario coupled with a lingering trough over Lake Superior are resulting in a tight surface pressure gradient which is supporting gusts to 25-30 mph in many locations. This combination of warm temps, low RH, and gusty winds maintains critical fire weather conditions over the area today with many locations hitting or flirting with red flag criteria per latest observations. The Red Flag Warning thus remains in effect through this evening for the central and western U.P. with a special weather statement in effect for the eastern third.

A stretch of active weather kicks off on Sunday as flow aloft pivots more southwesterly with the deepening of the trough over the western CONUS, paving the way for a series of waves to eject out of the Plains towards the Upper Great Lakes through the early part of next week. The first or these wave arrives on Sunday, with precipitation spreading into the area later in the day ahead of a warm front crossing Upper Michigan Sunday night. Winds will shift easterly and remain gusty early in the day on Sunday ahead of this system, but temperatures will be a bit cooler in the 60s as high clouds spread into the region ahead of the approaching system. Therefore do not expect the same degree of mixing as RH values bottom out in the 30s or low 40s, thus limiting any fire weather concerns for early Sunday. Regarding showers and thunderstorms, guidance has trended a bit quicker with the arrival of rain over the area, as early as mid afternoon in the western and central U.P. and the evening in the east. Could see a few storms on the strong side into Sunday evening as instability increases to around 1000 J/kg MU CAPE and shear increases with the arrival of a LLJ. SPC maintains a marginal risk for severe weather across the western half of the U.P. through Sunday night.

Severe potential increases and expands further east into the U.P. on Monday with the arrival of the second wave and associated surface low, with MUCAPE increasing as high as 2000-2500 J/kg and and bulk shear values of 40-50 kt easily supporting more organized convection. SPC maintains a Day 3 slight risk (15% probability) for severe thunderstorms across much of the southern half of the U.P. on Monday, Will also need to monitor heavy rain potential Sunday into Monday as a rich feed of gulf moisture sends PWAT values into the 1.25-1.75" range which is above the 95th percentile of seasonal climatology for mid-late May. WPC maintains a marginal risk of enhanced rainfall through Monday, with HEFS guidance currently showing a 10-25% chance to get back to minor flood stage on a few western U.P. rivers. Will continue to monitor in the coming days.

Third wave and associated surface low arrives on Tuesday. Model soundings suggest more of a weak/elevated thunderstorm threat by this time as the layer near the surface begins to stabilize, but will continue to monitor trends in the coming days. Mid next week currently looking cooler and drier in the wake of the more active weather early in the week, but guidance begins to diverge as we get later into next week.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 146 PM EDT Sat May 16 2026

VFR conditions are expected through the TAF period. Deep mixing will continue bringing gusty 25-35 knot WNW'ly winds to all TAF sites today, with the strongest gusts expected at KCMX. A lake breeze from Lake Superior shifts winds N'ly at KSAW and KIWD around 23Z. Winds will become light after sunset and veer E'ly overnight.

MARINE

Issued at 355 PM EDT Sat May 16 2026

Southeast to south winds of 20-30 kts, strongest east half, continue into tonight as a low pressure tracks over far northern Ontario. A few gusts up to 40 kts are possible this afternoon and early evening near the eastern lakeshores due to downslope acceleration from a low level jet, but more stable air over the open waters should prevent frequent gale force gusts from occuring. Thus did not hoist any Gale Warnings. Significant wave heights are not expected to exceed 7 feet with this system.

Winds veer and diminish below 20 kts tonight and Saturday morning, remaining mostly 20 kts or less through the day. High pressure building in from the northwest veers winds easterly by Sunday with winds below 20 kts Saturday night. A low pressure approaching the region increases winds to 20-30 kts for Sunday and Sunday night. There is a 30-50% chance for gales over the western arm of the lake Sunday afternoon and evening. A secondary low Monday night and Tuesday brings winds back to 20-30 kts lakewide. Additional chances for gales are present with this system, but probabilities are capped at 30% as uncertainty regarding stability over the lake remains. Strong to severe storms are possible Sunday night into Monday as well as Monday night.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Red Flag Warning until 9 PM EDT /8 PM CDT/ this evening for MIZ002-004>006-009>014-084-085.

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