textproduct: Marquette

KEY MESSAGES

- Showers and isolated thunderstorms are possible in the central UP before dropping off shortly after 00Z.

- Patchy fog is possible inland late tonight into tomorrow morning, and dense marine fog is possible tonight into tomorrow morning.

- Sunday and Monday are expected to be dry and cool, and temperatures should remain below normal this week.

DISCUSSION

Issued at 321 PM EDT Sat Jun 20 2026

This afternoon, broad lift from a northerly, upper-level jet streak combined with diurnal instability are leading to rain and isolated thunderstorms across most of the UP. Radar returns currently show weak to moderate returns, mostly <40dBz and sometimes up to 55dBz at 0.5 degrees, tracking SE across the western and eastern UP, with the ENTLN showing almost zero lightning strikes. MRMS 3-hour accumulations shows swaths of up 0.2" and isolated spots up to 0.4", indicating that no cells have been particularly strong up to this point. Though radar shows no lake breeze yet, the HRRR has shown one initiating toward the central UP around 18Z, so these showers may see some extra diurnal lift very shortly with some cells developing into isolated thunderstorms. HREF 6-hour distributions show between 0" and 0.5" inches for locations in the south-central UP so once again, be prepared to experience a burst of rain should a cell track over you. Given the moderate diurnal influences, though, no severe storms are expected, and what storms do exist are anticipated to drop off shortly after 00Z.

Dense fog is in place along the west nearshore zones of the Keweenaw, with webcams showing the West Portage Canal Entrance socked in as well as points north along the shoreline. Given the light winds forecasted through the night and a layer of very low dewpoint depressions from the NAM & HRRR, this fog should stick around at least until tomorrow morning. Interior areas which see rainfall this afternoon may also experience dense fog tonight.

With the robust Hudson Bay/Canadian low finally moving toward the North Atlantic, weak surface ridging begins to build in Sunday as mid-level flow trends zonal. Heights over the region remain anomalously low as anothor mid-level, closed low drops down toward the CWA from western Ontario. This low is shunted to our north as the remnants of today's jet streak move from meridional flow toward zonal and propogate eastward. During this time, PWATs also remain anomalously low for this time of year, between 0.5" and 0.8", according to the EPS. Thus, Sunday and Monday look to be drier, with little to no accumulations, and still cool. Both days can expect highs in the mid 60s to low 70s, and lows down to 40 in the interior, and high 40s closer to the Great Lake shorelines.

By Tuesday morning, ensembles show a swath of high pressure extending from Ontario to the Midwest firmly in place. This is followed quickly by a weak surface low travelling from Saskatchewan and reaching MN/WI by Tuesday night. Along with this system, the UP could see rain and thunderstorm chances late Tuesday into Wednesday, though no serious impacts are expected. The cool trend is expected to continue through the week, as the ECWMF's EFI shows anomalously cold maximum and minimum temperatures through Friday.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 820 PM EDT Sat Jun 20 2026

VFR conditions will prevail into tonight at all TAF sites with any lingering rain showers and thunderstorms now south of the sites. Tonight, however, limited cloud cover and light winds at the surface will be conducive to fog development, especially after 09Z. MVFR conditions will be most likely in any fog formation, but there is a 30% chance of IFR visibilities at any of the terminals and especially at CMX. Look for fog to dissipate after sunrise.

MARINE

Issued at 321 PM EDT Sat Jun 20 2026

Light, generally northerly flow with winds and gusts <10kt prevail on Lake Superior and Bay of Green Bay through Thursday. Monday afternoon and night, the eastern part of Lake Superior may experience NW'ly gusts to 15 kt, and western Lake Superior may see NE'ly gusts on Wednesday during the day. Significant wave heights are expected to be mostly <1ft on Lake Superior, occasionally reaching 2ft through Thursday, and well below 1ft on the northern part of the Bay of Green Bay except for a brief period during the second half of Monday when they may reach 1.5ft.

Dense fog is in place along the west nearshore zones of the Keweenaw and is expected to stick around at least until tomorrow morning. Offshore zones in the west and east may also experience dense fog tonight.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... None. Lake Superior... Dense Fog Advisory until 8 AM EDT Sunday for LSZ242>244.

Lake Michigan... None.