textproduct: Marquette

KEY MESSAGES

- Scattered showers and a few thunderstorms will move from west to east across the UP tonight into Sunday morning. Overall rainfall will be light, less than a quarter inch though locally higher amounts can be expected with any thunderstorms that develop.

- Hazardous swim conditions are expected for the beaches along Lake Superior east of Marquette on Sunday due to high wave action and strong rip currents.

- Showers and thunderstorms will be possible Monday night into Tuesday.

- Temperatures will be close to seasonal averages most days through next week, with highs in the 70s and lows in the 40s and 50s.

DISCUSSION

Issued at 145 PM EDT Sat Aug 15 2026

Early this afternoon model 500mb height analysis and GOES water vapor imagery showed an upper level high pressure over the Gulf Coast states extending weak ridging into the Upper Great Lakes. Up stream a trough was over British Colombia, approaching the Pacific Northwest. Shortwaves were embedded in the flow ahead of the trough from the Midwest north into Manitoba, resulting in areas of showers and thunderstorms. The UP had remained dry so far with a decaying MCS over MO/IL/IN interrupting moist transport northwards. Skies ranged from partly cloudy in the east to cloudy in the west. Surface observations showed temperatures in the upper 70s to low 80s in the east but cooler, low 70s, in the west where clouds were keeping temperatures down. Winds were from the east and southeast 5-10 mph.

The chance for showers will increase tonight as a cold front approaches the UP. The best dynamics with the associated shortwave will stay north of the area, thus forcing will overall be lacking. Instability is also meager with poor lapse rates and skinny CAPE profiles. PWATs do approach 1.75" as the front moves through the area with dewpoints rising into the upper 60s to near 70 by Sunday morning. Therefor, any thunderstorms that do form will be capable of heavy downpours. That being said, heavier downpours will be relatively isolated with most of the UP will see precipitation amounts struggling to approach that of a wetting rain (0.10"). The front will exit the eastern UP on Sunday morning. Immediately behind the front a period of light rain or drizzle is possible in the western U.P. with upslope westerly flow. Skies should begin to clear during the afternoon as drier air filters into the area from the northwest. Higher dewpoints tonight will keep the airmass on the muggier side with lows in the 60s.

Northwest flow aloft is expected for Sunday night through much of the week with a seasonable, comfortable airmass providing highs in the mid to upper 70s and lows in the 40s and 50s. Another cold front will move through the U.P. Monday night into Tuesday bringing the chance for showers and thunderstorms. The GEFS and deterministic medium range guidance are trending faster with the front, moving it through Monday night into Tuesday morning. This scenario would limit thunderstorm chances as the frontal passage will not align with diurnal instability and large scale forcing and moisture return look marginal. The EPS is slower with the front with strong instability and shear which could result in stronger thunderstorms. Trends will continue to be monitored.

The next chance of showers will be late in the week as northwest flow brings another front through the area.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 145 PM EDT Sat Aug 15 2026

VFR conditions prevail this afternoon at all sites but will deteriorate tonight as showers work from west to east through Sunday morning ahead of and along a cold front. A few rumbles of thunder cant be ruled out as well, so opting to include prob30 groups for -tsra at each site, mainly between 03-09z. Behind the front by sunrise, IFR to LIFR ceilings are most likely (60-80% chance) at IWD and CMX in northwesterly upslope flow. Light winds will be the rule overnight, but gusty W to NW winds >15 kts will be present tomorrow.

MARINE

Issued at 145 PM EDT Sat Aug 15 2026

Lake Superior - Easterly winds 10-20kt are expected across the lake today ahead of an approaching cold front. A few thunderstorms are possible tonight into Sunday morning as the cold front pushes across the lake but the threat for hail or gusty winds with the storms is very low. Behind the front winds will become northwest 25-30kt east of the Keweenaw Peninsula. Elsewhere expect winds of 15-20kt. Winds become light and southerly Sunday night into Monday, less than 20kt. Another winds shift back to the northwest is expected on Monday night into early Tuesday as another front pushes across the lake with northwest winds up to 20kt.

Northern Bay of Green Bay and northern Lake Michigan - Southeast winds around 10kt will shift southwest tonight and northwest behind a cold front Sunday early afternoon, increasing to 20-25kt, strongest over northern Lake Michigan. A few thunderstorm may accompany the front but the threat for hail or gusty winds with the storms is very low. Winds diminish Sunday night to 10kt or less. Winds become southerly on Monday 10-15kt before shifting to the north around 10 kt behind a cold front on Tuesday.

MQT WATCHES/WARNINGS/ADVISORIES

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