textproduct: Marquette

KEY MESSAGES

- High temperatures trend upward through the weekend.

- Next chance for showers and thunderstorms comes with a cold front on Saturday. Can't rule out a few strong to severe storms, but probability is low.

- Another system brings additional rain and thunder chances Sunday into Monday, but forecast confidence is low.

DISCUSSION

Issued at 259 PM EDT Thu Jul 23 2026

Latest GOES water vapor and RAP analysis reveal northwest flow aloft across the Upper Great Lakes between persistent deep troughing over NE Canada and low amplitude ridging over the western half of the CONUS. This yields a pleasant summer afternoon across the UP with mostly sunny skies and highs generally in the upper 70s to low 80s. An embedded disturbance over northern Ontario could bring a few showers near Isle Royale through this evening, but otherwise expect mostly clear/sunny skies to prevail across the region tonight into Friday as surface high pressure lingers to the south across Lower Michigan. Thus expect similarly pleasant conditions on Friday as 850 mb temps inch up towards 15C and allow highs to warm a couple more degrees into the low to mid 80s for Friday afternoon.

The next chance for precipitation arrives on Saturday as a stronger low pressure system moves across northern Ontario and drags a surface cold front across the UP Saturday morning. Severe potential appears limited by timing as the best forcing will have departed to the east prior to peak heating, but will nonetheless have to monitor the potential for a few strong to severe storms as guidance depicts bulk shear values increasing to 35-40 kt with MUCAPE of 500-1000 J/kg through early Saturday. Thunderstorm chances will linger into the afternoon as shear remains adequate and warm and humid conditions allow the air mass to recover behind the front, but storms will be more hit or miss in nature given the lack of obvious forcing mechanisms. Precipitation amounts do not look overly impressive/impactful as the NBM depicts around a 40% chance to receive a wetting rain of a quarter inch or more across the northern tier of counties along Lake Superior, with closer to a 15-20% chance near the WI border and Lake Michigan. Would expect precipitation to be highly variable as locations that receive thunderstorms could see much higher amounts given PWATS of 1.25-1.50" on Saturday.

Rain and thunderstorm chances persist into Sunday and Monday as another system moving over the top of the upstream ridge approaches from the west, but uncertainty over the track of this system results in relatively low forecast confidence at this time. Chances on Sunday will revolve around the placement of a surface warm front ahead of the low, as expected high temperatures well into the 80s should yield plenty of instability to work with if the other elements come together. The next round of shower and thunderstorm potential will then come on Monday as the system tracks through the region. SPC is keeping the best severe probs south of the UP for both Sunday and Monday as of this writing, but will need to continue to pay close attention to the forecast as this will be highly dependent on the ultimate track and evolution of the system. Otherwise, the rest of next week looks fairly benign as the large scale pattern continues to favor a northwest flow regime with temperatures close to seasonal norms and periodic precipitation chances as embedded systems move through the region.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 126 PM EDT Thu Jul 23 2026

VFR conditions persist under weakening surface high pressure. Gusty SW winds upwards of 15 with gusts 20-25 kts will be common through the evening. Forecast soundings highlight a strong surface inversion developing tonight, thus winds should lighten below 15 kts, though a tightening pressure gradient to the northwest may keep SW winds breezy.

MARINE

Issued at 259 PM EDT Thu Jul 23 2026

Marine conditions look to remain fairly unsettled by July standards as a number of systems impact the area through early next week. A tight pressure gradient between low pressure to the north and surface high pressure to the south continues to produce southwest winds gusting to 20-30 kt across western Lake Superior and northern Lake Michigan through this evening, supporting small craft headlines across many of the nearshore zones. Look for a repeat on Friday as another low crossing Ontario brings another period of gusty winds Friday afternoon into Friday night. A passing cold front will keep the active pattern going into Saturday, also bringing a chance of showers and thunderstorms to the waters of the Upper Great Lakes. Could see a brief lull in winds and waves between systems on Sunday, but another system will move through the region and potentially bring more headlines by Monday.

MQT WATCHES/WARNINGS/ADVISORIES

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