textproduct: Marquette

KEY MESSAGES

- Today is expected to be dry and cool, and temperatures should remain below normal this week.

- Tuesday night through Thursday morning bring potentially widespread rain showers and thunderstorms.

UPDATE

Issued at 355 AM EDT Mon Jun 22 2026

The going forecast remains mostly on track this morning as the last of the Sunday showers is moving east and out of the CWA. GOES-East Nighttime Microphysics shows otherwise mostly clear skies in the wake of the showers with a few patches of low level fog (verified by isolated METARs and other reports of reduced vis). Once again, fog will be the main story of the morning as RAP analysis shows a weak pressure gradient across the Upper Midwest between a 1007mb low over Indiana and a 1022mb high on the western shores of Hudson Bay (15mb over 1400 miles). At 500mb, various shortwaves are tracked from IL to the Central Plains with closed lows over northeast Ontario and the southern Canadian Rockies separated by ridging. The lack of a strong pressure gradient is leading to mostly light winds and with mostly clear skies for radiational cooling to the Td and a moistened boundary layer from the earlier rain showers, the ingredients are in place for some dense fog, though models are widely spread on the coverage and intensity of such fog. LAMP guidance has struggled to resolve much fog at all, though the HREF shows widespread 30-60% probabilities of visibility falling below half a mile. Given the continued patchy nature, will carry on with a persistence forecast this morning as coverage so far does not warrant an advisory.

Dry weather is forecast through Tuesday morning as the closed low aloft shifts east of the UP and ridging over the Plains causes high pressure to build. The next chances for widespread precip look to be late Tuesday into Wednesday as the GEFS shows a cluster of 1010- 1015mb low pressures cutting from North Dakota to Wisconsin and lingering in the Great Lakes region through Thursday night. The disturbed weather in the midweek period will include some thunder chances as mean LREF SBCAPE by Wednesday afternoon is around 500 J/kg in some interior western locations, but confidence in low track and timing is too low to deviate from the NBM.

High pressure builds back in for Friday and next weekend, though the early next week period looks to be of note as the GEFS shows strong low pressure over the Plains (some members well into the 980s mb range) with various solutions bringing lows tracking near the Upper Great Lakes at some point in the first half of next week. The sustained southerly flow ahead of the cold front will bring warmer conditions (NBM highs in the 80s for next Monday) and the tighter pressure gradient is driving the highest probabilities of winds gusting over 20 mph in this forecast period (Euro ensemble probabilities at 70+%).

DISCUSSION

Issued at 349 PM EDT Sun Jun 21 2026 Amended at 355 AM EDT Mon Jun 22 2026

With a series of low mid-level heights feeding toward our CWA from western Canada, expect cooler pattern to continue through week. As Sunday's low moves east, weak surface high pressure settles into place through Tuesday. 850 mb heights remain anomalously low and winds maintain some northerly component, so expect highs in the high 60s and low 70s, and lows down to 40 inland and high 40s along the shorelines for today. Tuesday will be slightly warmer.

A low tracking from Manitoba on Tuesday brings in the next significant precipitation chances. Ensembles show a ~1014mb surface low dropping southeast from Minnesota late Tuesday, deepening to ~1012mb and reaching Green Bay by late Wednesday. The GEFS shows moisture reaching up the Gulf and resulting PWATs between 1" and 1.25" coinciding with system, and the RRFS indicates MUCAPE in the western UP up to 1000 J/kg. With more moisture available and decent instability potential, we may see more widespread rain showers along with non-negligible chances for thunder.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 707 AM EDT Mon Jun 22 2026

VFR conditions prevail at all sites and are forecast to remain so through the period. Winds will also be light throughout the period, with the strongest winds being around 10 kt at SAW in the afternoon, but otherwise most will be 5 kt or less. Fog tonight is only about 10% likely at all sites.

MARINE

Issued at 349 PM EDT Sun Jun 21 2026 Amended at 355 AM 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 15 kt.

A low tracks through the Upper Great Lakes on Wednesday, bringing with it widespread chances of showers and thunderstorms. Winds shift direction Tuesday evening through Thursday morning, depending on the track of the system. Sustained winds are light and wind gusts are are not expected to exceed 20 kts during this time. Significant wave heights should remain <2ft on Lake Superior and <1ft on the Bay of Green Bay.

The best chances for 20+ kt gusts in the next week comes late Sunday into next Monday, when deepening low pressure over the plains drives southerly gusts that are around 40% likely to exceed 25 kt.

MQT WATCHES/WARNINGS/ADVISORIES

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