textproduct: Detroit/Pontiac

KEY MESSAGES

- Showers expand into the area late afternoon and linger through early Friday morning.

- A strong cold front delivers gusty winds and much chillier conditions Friday, with a scattered showers. Lake effect rain showers develop over the Thumb by evening.

- Turning drier through the weekend with slightly warmer readings by Sunday.

DTW THRESHOLD PROBABILITIES

* High for ceilings at or below 5,000 feet through the TAF period.

* Low for thunder after 22Z today.

PREV DISCUSSION

Issued at 310 AM EDT Thu Oct 15 2026

DISCUSSION...

Influence of high pressure wanes over the course of the morning as it shifts into Quebec. As this occurs, the next weather maker takes shape over the Midwest as southern/northern stream waves phase resulting in developing low pressure near the upper-Mississippi. Associated surface warm front lifts through the Ohio Valley today with the elevated portions of the frontal slope lifting over southern lower MI. Actual activation of the slope however is delayed until late afternoon (~20-21Z) when lead vorticity/theta-e finally reaches the area favoring a greater coverage of moderate showers over the northern half of SE MI (north of M-59) through this evening. Secondary low feature along the occluding front over northern IN/OH remains present in higher res model output resulting in the surface warm front being confined on or just south of the Ohio border. An interesting potential outcome with instability being held south of the area and the main low track trending a touch further north towards the Saginaw Valley, is a corridor within the southern portions of the CWA (ranging somewhere from the M-59 to I- 94 corridors) of notably less shower development due to falling in between the areas of stronger forcing. This is scenario can be seen in the most extreme case in the NAM but a flavor of which is present in the ARW/HRRR. Areawide, general QPF is expected to range between 0.25-0.5" (highest north) though if the outcome above is realized, some locales could see only a tenth or so of rainfall.

Low departs into southern Ontario by Friday morning tapering off the majority of activity over SE MI. Parent mid-upper trough slides across lower MI during the day bringing significantly colder air aloft as 500mb temps fall some 20 degrees into the mid -20's C. This ongoing cold advection within the diurnal window steepens lapse rates as passing trough influence supports modest upper divergence. While the bulk of moisture is east of the region by this point, moisture wrapping around the mature low as well as lake flux should result in pretty good coverage (scattered to numerous) convective showers by midday with peak coverage in the afternoon aided by a secondary cold front dropping through the state. This front marks the lead edge of the more robust CAA as 850mb temps fall from roughly +6C to -3C by evening. Lake surface temps currently hover in the mid teens C so more than enough delta T to spark lake effect rain showers. Winds turn north post-front favoring these bands to work across the Thumb and down into Metro Detroit- particularly the eastern half.

For winds Friday, the gradient weakens following the low/initial cold front with lower level column wind within the mixed layer looking to support peak NW gusts up around 25kts (~30mph). This changes with the arrival of the secondary cold front late afternoon- evening, coincident with the passage of the trough axis, leading to a tightening gradient and column wind fields increasing towards 30- 35kts. Forecast soundings are favorable for sufficient mixing depths through the evening to tap into this flow to push peak N gusts to 35mph with 40mph likely along the Lake Huron shoreline.

Gusty winds and lake effect wind down Friday night as surface high pressure over the Midwest beings to expand into the central Great Lakes. Overnight lows bottom out in the lower 30s with sub-freezing temperatures expected in areas north of I-69 though areas on the glacial moraine could also see temps drop below 32F. Below normal temperatures in place for Saturday as continuing north wind leads to highs struggling to reach the mid 50s. Surface ridge axis eventually crosses Saturday night as central CONUS upper ridging expands overhead setting up southerly, warmer return flow for the new week. Ridging influence holds through at least the first half of the week, if not longer, maintaining an extended period of dry weather and above normal temperatures with highs in the mid 60s.

MARINE...

High pressure migrates from the northern Great Lakes into New England today, causing easterly wind to veer southeast. The gradient strengthens with time as low pressure over the mid-Mississippi Valley tracks northeast and into the central Great Lakes this evening. Showers expand in coverage from late afternoon into this evening and a few thunderstorms will be possible mainly near western Lake Erie and Lake St. Clair. As the deepening low center passes over lower MI overnight, a 45 to 55 kt southwesterly low-level jet will pass overhead near western Lake Erie. While profiles show strong low-level stability during this period which will hold most of the momentum aloft, potential exists for gusts to around 30 kt after midnight.

A strong cold front will pass north to south across the region on Friday as the low departs to the east. Increasing instability and favorable fetch offer relatively high confidence to see northerly gusts to 35 to 40 knot gales on Lake Huron Friday afternoon and Friday night. A Gale Warning is in effect for all of Lake Huron. Will monitor the need to expand the warning into Lake St. Clair and western Lake Erie, but confidence remains too low at this time. Gusty northwest wind backs to west-southwest by Saturday as high pressure builds into the Ohio Valley.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Gale Warning from 1 PM Friday to 4 AM EDT Saturday for LHZ361>363- 421-422-441>443-462>464.

Lake St Clair...None. Michigan waters of Lake Erie...None.