textproduct: Detroit/Pontiac

KEY MESSAGES

- Extended stretch of seasonably cool conditions will exist into the middle of the week.

- Aside from a low chance of rain early this week near the Ohio border, dry conditions are expected throughout the week.

DTW THRESHOLD PROBABILITIES

* High for ceiling at or below 5000 feet.

PREV DISCUSSION

Issued at 303 AM EDT Mon Sep 21 2026

DISCUSSION...

Southeast Michigan will remain positioned between loosely organized split upper level flow thru the early week period, as a sprawling 1028 mb high pressure system centered to the north maintains a high degree of influence. This pattern effectively retains east to northeast low level flow, ensuring a seasonably cool resident airmass holds firm during this time. 850 mb temperature projected to dip into the single digits, translating into highs both Monday and Tuesday of lower 60s most locations. Mainly dry with breezy conditions as the profile remains dominated by larger scale subsidence within a generally moisture starved profile. There remains a lower end rain chance near the Ohio border, as shortwave energy rippling thru the southern stream into the Ohio valley may engage the deeper moisture still lingering near the Michigan-Ohio border. Diurnal mixing will yield afternoon wind gusts generally in the 20 to 25 knot range - slightly higher downwind of Saginaw Bay.

Weak upper level system will drift across the Ohio valley throughout the mid-week period. This system will attempt to pull moisture north and west toward the area Tuesday night into Wednesday. Broader ascent offered by some degree of deformation may prove sufficient toward generating some pockets of showers during this time, again mainly for areas south of the I-94 corridor. Otherwise, stretch of dry and stable conditions lasting through the end of the work week. Lack of meaningful thermal advection as low level flow holds out of the east-northeast maintains this stretch of below average temperatures. Highs in the 60s with overnight lows dipping into the mid to upper 40s.

The closed upper level low over the Ohio Valley is forecast to open up into a progressive trough and fill as it gets absorbed into the primary northern stream westerlies by Friday. Simultaneously, the expansive surface anticyclone centered over northern Ontario/Quebec will slowly shift eastward toward the Canadian Maritimes. Building upper heights locally will solidify a gradually moderating thermal profile while maintaining dry and stable background conditions. 850 mb temperatures will ease back toward the 10c range, allowing readings to work back toward seasonal averages under nearly full insolation. No rain expected thru the upcoming weekend, as conditions remains governed by low and mid level ridging.

MARINE...

The central Great Lakes reside on the southern fringe of broad northern Ontario high pressure through the first half of this week. The combination with a lingering stalled frontal boundary over the Ohio Valley results in a respectable gradient across the region maintaining moderate northeasterly winds through Tuesday (gusting 20- 25kts with 30kts possible in the Saginaw Bay). Disturbances rippling along the frontal boundary could offer some sporadic shower chances over the southern Great Lakes though influence of high pressure is expected to keep most of the area dry. Westward drift of high pressure leads to a shift toward more easterly flow Wednesday though with little to no reduction in wind speeds. Gales remain unlikely though onshore flow warrants long duration Small Craft Advisories for all nearshore waters.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None.

Lake Huron...Small Craft Advisory until 10 PM EDT Wednesday for LHZ421-422- 441>443.

Lake St Clair...Small Craft Advisory until 10 PM EDT Wednesday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EDT Wednesday for LEZ444.