textproduct: Detroit/Pontiac

KEY MESSAGES

- Showers move into the area late this afternoon, expanding in coverage and intensity overnight.

- A cold front delivers gusty winds (+35 mph) and chillier conditions Friday, with periods of showers.

- Frost/freeze conditions are possible Friday night into Saturday morning with temperatures minimizing in the low 30s.

- Turning drier over the weekend and through the first half of next week with a gradual warm-up starting Sunday.

DISCUSSION

High pressure exits as rain approaches, with showers now being sampled via KDTX radar over western Lower Michigan. These initial showers will first fill in over the Tri-Cities, before spreading across the rest of Southeast Michigan this evening. This latest bout of rainfall is tied to the downstream effects from the phasing of a progressive northern stream longwave trough and a southern stream low, now opening up over the lower Missouri basin. Meanwhile, the resulting surface low is currently lifting across Illinois, deepening as it tracks toward Lake Michigan while sustaining a broad region of showers under the wider cyclonic influence. Warm/moist advection is underway as a rich theta-e plume gets shoved into the Ohio Valley, ahead of the inbound cold front. Expect a sharp uptick in coverage and rainfall rate after this plume engages the stronger dynamics, once the elevated warm nose makes further inroads into the region.

Given the pace and trajectory of this low, timing issues do exist in pairing the more robust forcing with a deeper moisture layer. Hi-Res models still depict large differences in the deformation/FGEN axis of the higher rainfall amounts. It is still plausible for a narrow stripe of 0.75+ inches of QPF to set up somewhere over the forecast area, generally along a southwest to northeast line. The aggregated NBM suite has this corridor bisecting the Tri-Cities and Thumb areas. Timing-wise, the peak of the event should center between the hours of 7 PM and 1 AM. Forecast soundings are not very bullish in developing unstable layers, but still can't completely rule out an isolated rumble of thunder given upstream convective activity. Should also note that shower residence time ought to be higher over The Thumb once the lake effect influence takes root.

With the low exiting into Lake Huron around 09Z Friday, rainfall should drop off quickly once the initial cold front works through. This veers winds west-southwesterly through the first half of the day with temperatures holding steady in the mid 50s. Additional showers will be possible Friday afternoon as the secondary cold front sweeps through, marked by a sharp northwesterly wind shift, uptick in wind/gust speeds, and brisk cold advection. Gusts in the 35-45 mph range may arise on Friday. First, with the trailing low- level jet overnight into the morning hours during a period of higher stability, then again during the afternoon/evening once the mixed- layer deepens from the frontal passage. The main area that could see borderline Wind Advisory criteria exists over The Thumb, given the lower friction and northerly flow off Lake Huron. The instability created by the front should also wring out lingering moisture in the form of rain. Any shower development associated with this activity should be rather light and brief. Aggressive post-frontal drying and cooling then yields a clear and crisp night with many locations likely to drop below freezing, more so outside of Metro Detroit. Frost/freeze headlines will likely be needed Friday night into Saturday morning with temperatures minimizing in the low 30s.

Drier conditions settle in over the weekend as surface high pressure expands out of the Plains. Chilly, but less windy, on Saturday with highs about 10F below average, in the low-mid 50s. The surface ridge then centers over Appalachia Saturday night into Sunday, leading to a local gradient wind shift toward the southwest. This helps boost readings back up to seasonal normals (low-mid 60s) by Sunday. Rain- free weather likely persists through the first half of next week while split-flow situates overhead. Expect highs to run a few degrees above normal next week.

MARINE

Showers increase in coverage and southeast winds strengthen this evening as low pressure approaches from the mid-Mississippi Valley. As the system crosses southern Lake Michigan shortly after midnight, its warm front lifts across Lakes Erie and St. Clair which causes wind direction to veer to southwest. A strong 40 to 50 kt low-level jet passes over this area, supportive of wind gusts to around 30 kt to reach the surface mainly before dawn. The deepening surface low tracks across Lake Huron Friday morning, pushing a strong cold front southward across the region through the rest of the day. Rapid cold advection leads to increasing instability while northerly wind direction offers favorable fetch down the long axis of Lake Huron. This produces a powerful wind field that peaks late Friday afternoon into the evening. Probabilities remain high for gusts to 35 to 40 kt gales and a Gale Warning remains in effect for all of Lake Huron. Lake St. Clair and western Lake Erie may see a brief period with gusts to 35 kt, but given the unfavorable fetch, any gales are expected to be brief.

Lake effect showers and gusty northerly wind continue through Friday night before a ridge of high pressure builds into the Ohio Valley, shifting wind to southwest Saturday afternoon into Sunday. A tightening pressure gradient offers potential for winds to increase back to gale force across Saginaw Bay and out into the open waters of Lake Huron during the day Sunday.

PREV DISCUSSION

Issued at 109 PM EDT Thu Oct 15 2026

AVIATION...

Expansive area of MVFR stratus entrenched throughout SE Michigan this afternoon, as moist low level easterly flow holds downstream of an inbound low pressure system. Deepening moisture depth will support an increase in shower coverage this evening, while bringing an accompanying reduction in cloud base to IFR with time through early tonight. Prevailing east/southeast wind this evening shifts to southwesterly with the passage of the low overnight. There remains a small window for a noted increase in wind magnitude off the surface to generate low level wind shear, but expectation remains for these winds to progressively translate into gusty surface conditions /20 to 25 knots/. Gusty westerly wind gradually veering to northwest Friday, with additional pockets of showers possible. Gradual improvement in cigs back into MVFR likely early in the day. Secondary stronger cold front arrives Friday afternoon and early evening, offering a brief increase in gust potential from the northwest, potentially in excess of 30 knots.

D21/DTW Convection...Very low probability for an isolated thunderstorm to develop between 22z and 06z tonight.

DTW THRESHOLD PROBABILITIES...

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

* Low for thunder 22z-06z tonight.

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...Small Craft Advisory from 10 PM this evening to 10 AM EDT Saturday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 10 PM this evening to 10 AM EDT Saturday for LEZ444.