textproduct: Marquette

KEY MESSAGES

- Warmer than normal temperatures through early next week.

- Low humidity paired with gusty winds and warm temperatures today will lead to elevated to critical fire weather conditions. Red Flag Warnings are in effect for most of the U.P. today.

- Heavier rain showers as well as strong to potentially severe storms early next week.

DISCUSSION

Issued at 258 AM EDT Sat May 16 2026

Early this morning GOES satellite water vapor imagery and GFS model height analysis showed a shortwave through, which was weakening and opening up over northern Ontario, with relatively zonal flow over the western half of the U.S. One exception of a subtle shortwave ridge over the northern Rockies. Radar imagery showed an area of more widespread showers and thunderstorms over the eastern U.P. with isolated to scattered thunderstorms over the central U.P. This activity is expected to exit the area over the next 2 to 3 hours as a weak cold front over the western U.P. pushes through. RTMA showed dew points had recovered quite a bit over the central U.P., into the mid and upper 50s.

A cold front will exit the area this morning and a surface high pressure will begin to build into northern Ontario. Behind the cold front cold air advection aloft and dry air in the low levels will allow for deep mixing today over the U.P. This will help mix down dry air resulting in humidity falling to around 20% with temperatures in the 60s north to 80s south. Additionally gradient flow and mixing will bring wind gusts to 35 mph over the western and central U.P. A secondary cold front will drop south across the area this afternoon bringing a wind shift to the north, especially over the eastern U.P. where the lake/land temperatures gradient will help accelerate the front. There will be some humidity recovery behind the front as temperatures cool. That being said, critical fire weather conditions will be in place during the late morning and afternoon hours over most of the U.P. with the exception of the far east and Keweenaw which will have elevated but not critical fire weather conditions. Red Flag Warnings are in effect and special weather statements will be needed for the far east and Keweenaw to highlight the elevated conditions.

High pressure influence persists through early Sunday afternoon. Saturday night will be cooler in the mid 30s to mid 40s, warming up on Sunday into the 50s to low 70s, coldest in the Keweenaw and near the Great Lakes. RH guidance has trended slightly more moist on Sunday as earlier precip and cloud cover onset prevents efficient warming and mixing to dry out the lower levels. Borderline elevated fore weather conditions are anticipated, but this ultimately will depend on onset timing of clouds and precip.

Attention then turns to a trough over the Rockies which sends shortwaves and possibly multiple surface lows over the region Sunday night through Tuesday as a ridge builds over the east coast. Overall expecting multiple rounds of showers and storms Sunday night through Tuesday. A warm airmass with a good Gulf connection ahead of these waves primes the region with ample moisture (PWATs between 1.25 and 1.75 inches) and instability. A warm front, strengthening LLJ, and the first shortwave bring a round of showers and storms by Sunday night. Guidance has trended convection arriving as early as the afternoon in the west. Steep mid level lapse rates, strong bulk shear (at least 40 kts), and elevated instability ~1000 J/kg could yield some strong to severe storms bearing hail and wind threats. There is a 30-60% chance for up to 1 inch of rain over the far west with this round. Instability increases through Monday to between 1000-2000 J/kg alongside maintained steep lapse rates and sufficient bulk shear. This maintains strong to severe storm potential with trailing shortwaves and the second surface low moving through the region. Chances for greater than 1 inch of rain increase UP wide Monday into Tuesday to 30-60%. Discrepancies remain in the upper pattern progression and surface tracks to nail down details, but this should improve over the weekend as the trough makes landfall over the Pacific Northwest. Will continue to monitor severe potential with the coming forecast packages. The SPC Severe Weather Outlook has expanded to include a marginal risk for the western two thirds of the UP on Sunday and maintained the 15% chance across much of the UP for Monday. WPC has a marginal risk for excessive rainfall over the far west Sunday night and across much of the UP Monday and Monday night.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 714 AM EDT Sat May 16 2026

VFR conditions are expected through the TAF period. Clouds will exit the U.P. this morning with deep mixing bringing gusty west-northwest winds to the TAF sites mid-morning through the afternoon. Winds will become light after sunset.

MARINE

Issued at 408 PM EDT Fri May 15 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 and Monday night.

FIRE WEATHER

Issued at 714 AM EDT Sat May 16 2026

Elevated to critical fire weather conditions are expected on Saturday across the entire U.P. Weak cold air advection with deep mixing will result in gusty westerly winds of 25 to 35 mph, strongest over the west half. This combined with highs in the mid 60s to low 80s and minimum humidities in the mid teens to upper 20s. A Red Flag Warning is in effect for much of the U.P. from late this morning through the early evening. The warning excludes northern Houghton, Keweenaw and Luce Counties where a SPS have been issued to cover the elevated fire weather conditions. A secondary cold front, aided by the lake/land temperatures gradient accelerates south this afternoon, especially over the eastern U.P. This will bring a wind shift to the north over the Keweenaw and portions of the eastern U.P. along with slightly cooler temperatures and some humidity recovery by early evening.

The potential for elevated fire weather conditions has become less likely on Sunday as guidance has sped up the arrival of low level moisture, precipitation, and cloud cover which will inhibit efficient mixing and drying.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Red Flag Warning from 11 AM EDT /10 AM CDT/ this morning to 9 PM EDT /8 PM CDT/ this evening for MIZ002-004>006-009>014- 084-085.

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