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KEY MESSAGES

-Near record breaking heat builds today and Tuesday.

-High pressure will continue with quiet and dry weather through Thursday.

-Rounds of showers return this weekend with chances of storms this Sunday.

DISCUSSION

Issued at 240 AM EDT Mon Jul 13 2026

Pattern Synopsis:

The 500 mb ridging pattern remains centered over the Northern Plains this morning and is expanding eastward into the Great Lakes region. Subsidence aloft will support continued surface high pressure and dry weather as H8 temperatures in the low to mid-20s (Celsius) advect into the northwoods from the southwest. As a result, surface temperatures will climb into the upper 90s, with a few areas near Saginaw Bay potentially reaching the low 100s.

The remainder of the week will see this ridging pattern continue to influence the majority of the Central U.S. Temperatures will begin to decrease after Tuesday due to an increasing Canadian airmass influence. A closed low pressure system, currently over Northern Hudson Bay, will progress southward over the Northeastern U.S. this weekend, bringing a return to more active weather. Waves of energy will pivot across the Great Lakes region, resulting in rounds of showers through the remainder of the forecast period, with increasing storm potential by this Sunday.

Forecast Details:

Today and Tuesday...A dry and hot southwestern airmass influencing the northwoods today and Tuesday will be the primary focus of this forecast cycle. Widespread afternoon highs are expected to reach the low to mid-90s today. Light westerly winds on Tuesday will push temperatures even higher, with a few locations near Saginaw Bay potentially breaking 100 degrees due to localized downslope warming.

The one silver lining to this heat wave, compared to previous events, is that dew points are expected to mix out into the 50s each afternoon. This will keep heat index values closely aligned with the actual ambient air temperatures.

Wednesday and Thursday...Midlevel heights will begin to lower across the Great Lakes Region thanks to the midlevel low over Northern Hudson Bay. The Thermal Ridge axis will retreat westward and bring surface temperatures back to the low to mid 80s across the CWA. Wednesday and Thursday will remain dry as continued subsidence continues surface high Pressure through Thursday.

Friday through Sunday outlook...Closed low pressure continues to progress southward this weekend and return precipitation to the Great Lakes Region. Forcing through embedded waves will deliver disheveled rounds of light showers at times starting this Friday. Probabilities of QPF remain low at this time mainly due to weak forcing combined with these systems beginning moisture-starved, but some areas of the midwest can expect more localized convective driven rain as a shortwave develops lee of the Canadian Rockies and digs across the Great Lakes Region this Sunday. Too early to determine impacts or rainfall potential, but we will monitor this feature as we head into late July.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 524 AM EDT Mon Jul 13 2026

The last of overnight showers/storms continue to depart off to the east early this morning. VFR conditions are expected to prevail across northern MI into tonight. Winds will increase out of the southwest this morning, eventually turning to west winds with gusts to 15-20 kts into this afternoon.

APX WATCHES/WARNINGS/ADVISORIES

MI...Heat Advisory from noon today to 8 AM EDT Tuesday for MIZ016>018-020>036-041-042-086>088-095>099. Extreme Heat Watch from Tuesday afternoon through Tuesday evening for MIZ041-042. MARINE...None.