textproduct: Detroit/Pontiac

KEY MESSAGES

- Some scattered showers tonight into Wednesday morning with a few rumbles of thunder, mainly south of M-59.

- More seasonable and drier during the day Wednesday, followed by additional rainfall Thursday afternoon into Thursday night.

- A strong cold front delivers gusty winds and much chillier conditions Friday, with a few showers in spots.

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

DISCUSSION

Aggressive low and mid level drying outpaced last evening's 00Z models, yielding clear skies since the mid-morning hours. GOES water vapor imagery continues to show widespread subsaturated air encompassing the Great Lakes while the exiting low's cold front slowly clears toward the Michigan/Ohio border. Taking into consideration the slow frontal progress, uninhibited insolation, and 850 mb temperatures hovering near 17C over Metro Detroit, recording breaking heat remains in reach today, given the previous record of just 83F. Further north, post-frontal flow has flipped west- northwesterly which will spread southeastward through the evening hours. The near-surface layer along the frontal slope cools faster than the rest of lower column, leading to a more abrupt end to the breezy afternoon conditions. Wind speeds drop off late tonight as pressure gradient influence shifts from the low to an upstream ridge of high pressure.

The 595 dam 500 mb Gulf Coast ridge remains anchored tonight as a plume of 800-600 mb moisture releases anticyclonically from the eastern Plains into the Ohio Valley amidst backing westerly flow. Meanwhile, the frontal boundary stalls just south of the state line as perturbed flow starts to work through aloft, helping trigger a period of scattered showers. Models preserve a relatively narrow QPF footprint with the highest totals (up to 0.25 inches) along/south of I-94, mainly over the southern four counties. Light/trace amounts are possible further north, up to M-59. In spite of RRFS forecast soundings showing an inversion layer from 2.5-6.5 kft, lapse rates above should suffice in generating pockets of 100-250 J/kg of elevated CAPE. As a result, a few rumbles of thunder cannot be ruled out.

There could still be a few lingering showers exiting the area by sunrise Wednesday, followed by mainly dry conditions settling for the rest of the daylight hours. Broad surface high pressure influence extending from Manitoba to Southeast Michigan ushers in a cooler continental airmass. The resulting shift to northerly flow helps to nudge the existing vicinity boundary further into the Ohio Valley throughout the day. Weaker winds expected as split-flow ensues below 700 mb, limiting gusts to less than 15 mph. The next round of showers arrives Thursday as a southern stream closed low lifts from the desert southwest into the Plains, phasing with a digging positively tilted longer wavelength trough. Supporting dynamics and a spike in upper level divergence will engage a robust theta-e plume lifting up the Mid-Mississippi Valley and eventually bringing rain to southern Lower Michigan. High uncertainty exists in the onset time for rain, reflected by the gradual northeastward expansion of Chance PoPs after 12Z, per NBM. The bulk of the rainfall should occur Thursday evening, or early Thursday night as the northeast flank passes over Southeast Michigan, well downstream of the deepening surface low, still located near the southern shores of Lake Michigan. The low then traverses southern Lower Michigan late Thursday night before crossing into Lake Huron Friday morning.

Turning colder and much windier on Friday as the system's cold front clears through. Aggressive constriction of the pressure gradient is possible in its wake, although there is a noticeable difference in the magnitudes of the deterministic solutions. The column will cool at similar rates, but should see the mixed-layer expand sufficiently for 35-45 knot lower tropospheric flow to mix down. Gusts in the 35- 45 mph range cannot be ruled out Friday afternoon and evening. Additionally, a deformation axis trails, which could help spur some light scattered rain showers. Chilly overnight with temperatures dropping near or slightly below freezing, particularly north of I- 69. Turning drier through the weekend with slightly warmer readings by Sunday, returning to climatological averages.

MARINE

Conditions remain very stable under southwest flow as air temperatures remain warm for this time of year which has tempered gust potential. There will be a window this evening where winds back to the west as low pressure departs the region. This window of backed flow is where elevated mixing depths just will be high enough to where gusts around 20 to 25 knots are possible. Small Craft Advisories remain in effect from the Saginaw Bay to Port Huron for this potential. Any elevated winds will then quickly diminish in the later evening hours as the pressure gradient rapidly weakens.

A cold front will then push through the Great Lakes tomorrow, stalling across southern Michigan by the afternoon. The favorable northwest fetch will produce wind gusts 20 to 30 knots across northern Lake Huron. High pressure to then build in through Thursday which will bring a period of light winds for the day. Confidence is increasing for a strong cold front to pass Friday into Saturday. Instability will increase over the lakes in the wake of the front as cold air flows over the warmer waters. Coupled with longer duration northwest flow, a high-end gale event is looking increasingly likely to end the week.

CLIMATE

Record high max temperatures for October 13th:

Detroit: 83 Degrees (Set in 1975) Flint: 83 Degrees (Set in 1975) Saginaw: 86 Degrees (Set in 1930)

PREV DISCUSSION

Issued at 1250 PM EDT Tue Oct 13 2026

AVIATION...

Southwest to west winds gusting 20 to 30 knots early this afternoon will drop off quickly and veer to the northwest to north this evening. MVFR clouds over northern Lower Michigan will gradually settle south tonight, enhanced by some shower development over southern Lower Michigan. A slight chance of a thunderstorm exists over the southern tafs as well, but chances are too low too include. Low clouds around tomorrow morning are expected to mix out during the afternoon as subsidence and drier air settles into the area with light northerly flow.

D21/DTW Convection...A passing wave to the south as a weak cold front sags through tonight offers a low chance for isolated thunder; however probability at the airport is too low to mention in TAF.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms tonight.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until 8 PM EDT this evening for LHZ421-422- 441>443.

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