textproduct: Detroit/Pontiac

KEY MESSAGES

- Warm and humid conditions will exist today and Tuesday. This brings the risk for severe weather each day, mainly during the afternoon and evening hours. Thunderstorms will be capable of producing damaging winds, large hail and isolated tornadoes.

- Cooler and drier conditions expected Wednesday and Thursday.

DTW THRESHOLD PROBABILITIES

* Moderate for thunderstorms this afternoon.

* Low for ceilings aob 5000ft through this morning. Moderate with thunderstorms this afternoon.

PREV DISCUSSION

Issued at 307 AM EDT Mon May 18 2026

DISCUSSION...

Warm frontal boundary responsible for the prolific hail producing supercellular activity across portions of the Saginaw valley and northern thumb late Sunday will finally ease north of the region this morning as higher magnitude warmth increases influence within deepening southerly flow. Benign conditions ensured thru late morning as stability holds under modest capping. Influx of higher quality moisture will commence during this time, establishing a notable moisture gradient from west to east by early afternoon /dewpoint of mid 60s west to upper 50s east/. This affords a moderate level of diurnal boundary layer destabilization for at least western sections. Given an afternoon temperature of middle 80s, mlcape projection of upwards of 1500-2000 j/kg will peak across the Saginaw valley and down through the Highway 23 corridor. This leaves a receptive downstream environment for potential reorganization/ expansion of any MCV governed remnant nocturnal convective activity spilling downstream. A fairly strong model consensus exists on this scenario, targeting lower Michigan for a mid-late afternoon increase in coverage. A broader threat window locally between 19z and 01z with dependence on pace of the MCV. The background wind field remains modest, but subject to a localized meaningful increase both across the lower levels and with greater depth as the feature moves through. Supportive environment to offer a risk of both large hail and damaging wind gusts, with greater overall potential with westward extent. A focused area of higher SRH does materialize as low level flow backs briefly with a slight shift in the pressure gradient orientation. Therefore, cannot completely discount the possibility for a more organized, rotating updraft to present a brief, isolated tornado threat. Outside of the convective window, forecast continues to highlight gusty southerly conditions reaching 30 to 35 mph at times today.

The seasonably warm and humid conditions will exist again Tuesday ahead of a cold front. A more muddled early day picture in terms of both cloud cover and precipitation chances, as a portion of the model solution space suggest possible activity prior to 18z owing to some combination of the ongoing moisture advection and remnant midwest convection leftover from tonight. Degree and pace of destabilization certainly still subject to change. Assumption for at least a weakly unstable environment timed favorably with an evening cold frontal passage will present an opportunity for deeper updrafts to organize within a sufficient background deep layer wind field along the frontal zone. The SPC Day 2 outlook maintains a slight risk designation to highlight the associated strong wind and large hail threat for the late Tuesday period. Warm sector environment will again become diurnally gusty, with winds reaching 30 to 35 mph from the south at times.

Notably cooler post-frontal environment arrives Wednesday. This will occur with the backdrop of increasing low to mid level ridging, ensuring a stretch of dry and stable conditions lasting into Thursday. Low level thermal trough marked by 850 mb temperatures of lower single digits, lending to below average readings during this time. Coldest conditions Thursday morning as the surface high centers locally - lows dipping into the 30s in some locations. Dry conditions likely to hold under a modest warming trend Friday, as the next system organizes upstream. This system will introduce the next chance of rain Friday night into Saturday.

MARINE...

A warm front releases north across Lake Huron this morning, with southerly winds expanding across all local waters. Strong low level jet winds will struggle to mix down over the open waters where cool water temperatures maintain stable over-lake conditions. Gusty southwest flow will thus be confined to the nearshore waters, aided by warmer water temperatures and land influence. Frequent gusts today and Tuesday are expected to hold between 25 and 30 knots, but an isolated gust to 35 knots over Saginaw Bay cannot be entirely ruled out. Small Craft Advisories are in effect for today and will be needed Tuesday as well. More localized wind/wave impacts arrive with thunderstorm activity this afternoon-evening, and again Tuesday when a cold front sweeps through the area. There is potential for some of these storms to be strong to severe with all modes of severe weather in play. The cold front comes through Tuesday night, followed by high pressure filling in mid-week to support a quieter and more seasonable late May pattern.

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.

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

Michigan waters of Lake Erie...None.