textproduct: Marquette

KEY MESSAGES

- Below normal temperatures continue through Thursday, with Tuesday being the warmest and almost normal.

- Tuesday night through Thursday morning brings periods of rain and thunderstorms, with the most active weather in the west.

- Warmer temperatures and increased moisture arrive Sunday and Monday, leading to rain and thunderstorm potential.

DISCUSSION

Issued at 333 PM EDT Mon Jun 22 2026

Dry and cool conditions rule the day today and tomorrow. Current RAP13 analysis and surface observations show the UP sitting under weak ridging with little wind. Thanks to pressure gradient flow, the the wind picks up slightly this evening out of the north before settling back to calm for tomorrow. At the WFO office in Negaunee, yesterday marked the eighth consecutive day with below normal high temperatures. Expect this to continue through Thursday, although the warm front associated with an incoming low will bring temps on Tuesday up to nearly normal.

Ensembles show a weak, 1014mb low dropping southeasterly from northern MN throughout the day on Wednesday, deepening slightly to 1012 mb and reaching Green Bay by early Friday morning. CAMS are in agreement that measurable rainfall will reach western end of CWA by 03Z on Wednesday, overspreading the UP by Wednesday afternoon. The RRFS shows a several-hour window between 1 and 4 pm on Wednesday with MUCAPE >1000 J/kg, along with moderate shear. The CWA is currently outlooked in SPC's 'General Thunderstorms' category for Day 3, though if these CAPE and shear values are realized, a strong thunderstorm or two can't be ruled out. At the high end, NBM shows areas in the western UP with 85% probability of receiving >0.5" of rainfall for a 24-hour period ending Thursday at 2AM. At the low end, less than 20% for the same field and timeframe is indicated for the eastern UP. Thus, this system should result in periods of rain and thunderstorms throughout the day on Wednesday, with the most active weather occuring in the west.

Nonzero PoPs taper off throughout Thursday, and temperatures remain cool. Mid-level ridging builds over the CWA towards the weekend. Ensembles agree that this ridge will amplify strongly over the eastern half of the US by Sunday, though differences exist in onset timing and duration. Per WPC, analysis of clustering solutions of 500 mb heights shows uncertainty in the Sunday-Monday (Days 6-7) timeframe with how quickly ridge-trough couplet shifts east. NBM high temperatures echo this uncertainty: interdecile spread for highs on Sunday and Monday is between 15 and 20 degrees for the entire CWA, ranging between the low 70s and low 90s. That said, the EPS indicates that low-level flow brings Gulf moisture north during this time (think 1.75" - 2"), raising potential for heat risk and active weather..

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 125 PM EDT Mon Jun 22 2026

VFR conditions are expected at all terminals in this period. Daytime cloud cover will erode with the setting sun and winds will go light and variable overnight.

MARINE

Issued at 333 PM EDT Mon Jun 22 2026

Light, generally northerly flow with winds and gusts <10kt prevail on Lake Superior and Bay of Green Bay through Tuesday. This afternoon and tonight, the eastern part of Lake Superior may experience NW'ly gusts to 20 kt.

A weak low tracks through the Upper Great Lakes on Wednesday, bringing with it widespread chances of showers and thunderstorms. Sustained wind speeds remain below 15 kts during this time. Winds on the Bay of Green Bay shift southerly as the low approaches on Wednesday morning; winds on Lake Superior go easterly. As the center of the low tracks through the UP overnight on Wednesday, winds on the Bay of Green Bay veer suddenly to westerly, and those on Lake Superior veer to northerly. Western and central portions of Lake Superior may see gusts to 25 kt on Wednesday afternoon and evening. As the low departs to the east on Thursday morning, all winds shift to northerly.

Significant wave heights on Lake Superior may build to 3ft for several hours Wednesday overnight, but otherwise remain <2ft on Lakes Superior and Michigan through Thursday.

As the region comes under high pressure on Friday, winds go calm (<10kts) until Saturday evening. Waves are forecasted to be <1ft Friday and Saturday.

MQT WATCHES/WARNINGS/ADVISORIES

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