textproduct: Marquette

KEY MESSAGES

- Warmer than normal temperatures through early next week.

- Low relative humidities paired with gusty winds and warm temperatures today and Saturday lead to elevated to critical fire weather conditions. Red Flag Warnings remain in effect for the far west today where critical fire weather conditions are expected. A Fire Weather Watch is in effect for most of Upper Michigan tomorrow.

- Scattered showers and thunderstorms will develop over the central and eastern U.P. this evening. Gusty winds are possibly with any showers or thunderstorms that develop.

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

DISCUSSION

Issued at 346 PM EDT Fri May 15 2026

Afternoon GOES WV imagery and RAP analysis show a closed low over northern Manitoba and a closed low over the northeast coast, pinching a ridge over southern Ontario. At the sfc, a 986 mb low is moving over far northern Ontario extending troughing down into the midwest while a weak high pressure continues shifting east toward the Atlantic coast. Upper MI is now in the wake of the warm front/shortwave rain showers and under clear skies. The tightening pressure gradient this afternoon, passing 40 kt LLJ, WAA, and sunny skies are setting up a warm, breezy and dry afternoon. Particularly dry conditions are focused in the west where Red Flag Warnings are in effect; elevated fire weather conditions in the Keweenaw and central. Although the LLJ will decay moving into tonight, mixing continues to increase (potentially all the way up to 500mb) keeping gusty winds (20-35 mph) into this evening. Highs are expected in the mid 70s to mid 80s west and mid 50s to low 70s east where onshore flow moderates conditions.

Medium and CAM guidances still are suggesting isolated to scattered showers and storms developing over northern WI central Upper MI, advecting eastward into tonight as a diffuse cold front presses in from the west. The abundant sunshine and a surge of moisture from WI late today will promote destabilization with MUCAPE values increasing to 500-1000 J/kg ahead of the front. The combination of ample dry air, with classic inverted-v thermodynamic profiles and strong winds in the mid-levels will bring the threat for gusty and erratic winds with any showers or storms. This will be especially true during the early evening hours when the low levels will remain well mixed. SPC has issued a marginal risk for the south-central and interior west. Otherwise tonight will be mild with lows in the upper 40s to 50s. Humidity recoveries will be poor tonight over the west, 50-60% range.

Zonal flow on Saturday with an elongated mid level wave grazing the northern tier of the CWA. Once lingering showers exit the UP in the early morning, dry weather persists the remainder of the day under clear skies. Breezy west winds start the day off, gusting into the 20-35 mph range, but taper off in the afternoon as the gradient flow weakens and weak ridging begins building in from the Canadian Prairie. Highs will be in the 60s to low 80s, warmest south-central. With efficient mixing and warm temps lowering RHs into the 20s to teens for much of the interior, opted to hoist a Fire Weather Watch for most of the CWA...excluding northern Houghton, Keweenaw and Luce Counties. Likely will see a SPS for those remaining areas with tonight's forecast package.

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 /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 739 PM EDT Fri May 15 2026

VFR conditions are expected throughout the TAF period over the terminals tonight and Saturday, even as some elevated -SHRA/TSRA could be seen at SAW tonight. In addition, with the winds weakening at the sfc tonight, expect LLWS to develop at CMX and especially SAW once the gustiness dies down; winds look to remain S to SW'rly tonight, before becoming W and eventually NW'rly on Saturday behind a 'cool front'. Expect the winds to become gusty once again by the afternoon hours on Saturday.

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 346 PM EDT Fri May 15 2026

Critical fire weather conditions are developing over the western UP this afternoon as southwest winds are gusting up to 30-35 mph with RH falling into the 20% range and temps in the upper 70s to mid 80s. A Red Flag Warning remains in effect for the western UP through 9 PM EDT/8 PM CDT. Elevated fire weather conditions are ongoing over much of the central UP and in parts of the Keweenaw. Modified flow off Lake Michigan will maintain a cooler airmass with higher humidity of 35-50% in the east.

Poor humidity recoveries are expected tonight, only around 50% in the west. Elevated showers and thunderstorms could bring gusty and erratic winds to 45-60 mph over the central UP this evening (especially early) with very dry low levels and strong winds aloft increasing the wind threat.

Elevated to critical fire weather conditions are expected on Saturday across the entire UP. 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 for much of the interior prompted a Fire Weather Watch for much of the UP. The watch does exclude northern Houghton, Keweenaw and Luce Counties where a SPS likely will be needed on the next forecast package.

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 until 9 PM EDT /8 PM CDT/ this evening for MIZ002-004-009-010-084.

Fire Weather Watch from Saturday morning through Saturday evening for MIZ002-004>006-009>014-084-085.

Lake Superior... None. Lake Michigan... Gale Warning until 11 PM EDT this evening for LMZ221-248-250.