textproduct: Detroit/Pontiac

KEY MESSAGES

- Warm and humid conditions exist again today which supports a risk of severe thunderstorms during the afternoon and evening hours. The strongest storms are capable of damaging wind, large hail, and isolated tornadoes.

- A cold front Tuesday night ushers in dry and cooler weather for Wednesday and Thursday.

- The next chance of rain arrives late Friday and Friday night.

DTW THRESHOLD PROBABILITIES

* Medium for thunderstorms this afternoon and evening.

* Medium for ceilings at or below 5000 ft today into tonight.

PREV DISCUSSION

Issued at 310 AM EDT Tue May 19 2026

DISCUSSION...

Higher magnitude warmth and humidity for mid May entrenched locally early this morning, as the area holds within deep layer south- southwest flow for one final day. Forecast for today offers a more muddled picture in terms of convective potential, scale and timing relative to that noted yesterday. Intermittent bouts of meaningful moisture advection will deliver another surge of higher quality theta-e early in the day, providing some potential for greater cloud cover to exist along with the possibility for some pockets of convective showers. With that, expectation for gradual boundary layer destabilization with time as intervals of greater insolation capitalize on the elevated dewpoint (mid-upper 60s), yielding upwards of 1500 j/kg of mlcape by late afternoon. There is a definitive model signal for higher instability to exist southeast of a Howell to Sandusky line, but with the best instability (2000+ j/kg of mlcape) remaining across Ohio. Convective focus most likely along some composite pre-frontal trough or remnant convective vort max out ahead of the main cold front within the 19z to 00z window, offering the greatest potential for more meaningful updrafts to emerge mainly within the aforementioned main instability gradient. Background wind field generally modest overall, but with potential again for some local enhancement should the convective response be governed by a stronger convective wave. This maintains an opportunity for organized late day convective development carrying a risk for strong winds and large hail. Afternoon temperatures peaking in the upper 80s/near 90 across portions of metro Detroit and points south and mainly mid 80s elsewhere. Warm sector environment will again become diurnally gusty, with winds reaching 30 to 35 mph from the southwest at times.

A few lingering showers around early tonight as the cold front settles through the region. Otherwise, turning notably drier and cooler as the post-cold frontal environment settles into region overnight into Wednesday. Deep layer stability held within prevailing low to mid level ridging affords dry and seasonably cool conditions lasting into Thursday. A standard moderation of the existing airmass then occurs Friday under a high degree of insolation and increasing upper height field, but still lacking in meaningful warm air advection. Highs the remainder of the week mainly in the 60s. Coldest readings noted Thursday morning, reaching into the mid and upper 30s in some locations.

Southern stream shortwave forecast to eject from the southern plains into the great lakes this weekend. Increasing magnitude of mid level southwest flow downstream of this wave will drive a notable surge of moisture advection directly into Lower Michigan Friday night. While some higher based light showers are possible late Friday as the column gradually saturates, the main window for widespread, meaningful rainfall will arrive Friday evening and persist overnight. Model guidance is coalescing around a broad swath of mainly stratiform rain with embedded elevated convective elements sweeping from southwest to northeast across Southeast Michigan. Precipitation may carry over into early Saturday, before chances taper off into the afternoon. Otherwise, generally seasonable conditions for the weekend period.

MARINE...

A warm and humid airmass over the cooler waters of the Great Lakes will support the development and expansion of dense marine fog. Sustainment of fog will be likely through the morning hours as a strong inversion holds overhead, and will likely continue to some degree through the early afternoon until a cold front mixes out the layer. As a result, a Dense Fog Advisory has been issued through the afternoon. Otherwise, calm to lighter winds hold overnight with some limited chances for isolated showers and thunderstorms. Southwest flow increases in magnitude during daylight hours tomorrow which will bring wind gusts around 20 to 25 knots through the Saginaw Bay and along the nearshore areas which have resulted in renewed Small Craft Advisories. The development of strong to severe thunderstorms will be possible again in the afternoon and evening, favored across southern Lake Huron and locations south. Wind gusts aoa 50 knots will be the primary hazard for severe weather development. Passage of the cold front will end the severe weather threat, veering winds from the southwest to northwest through the evening. High pressure builds behind the front, bringing lighter winds through the midweek period.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory from 10 AM this morning to 10 PM EDT this evening for LHZ421-422-441>443.

Dense Fog Advisory until 4 PM EDT this afternoon for LHZ361>363- 462>464.

Lake St Clair...Small Craft Advisory from 10 AM this morning to 10 PM EDT this evening for LCZ460.

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