textproduct: Detroit/Pontiac

KEY MESSAGES

- Generally cool through the afternoon before a warm front lifts through this evening. Showers and a few rumbles of thunder this morning.

- Additional rounds of showers and thunderstorms likely this evening and overnight. Highest chances for strong to severe storms will reside west of US-23 with gradually decreasing chances further east you are.

- Drier and still mild Friday, followed by additional showers and thunderstorms Friday night and Saturday.

- Below normal temperatures return Sunday into early next week with a few additional showers.

DTW THRESHOLD PROBABILITIES

* High for ceiling at or below 5000 ft today, moderate this evening, then high late tonight and Friday morning.

* Low for thunderstorms this morning, moderate to high this evening, and low late tonight.

PREV DISCUSSION

Issued at 439 AM EDT Thu Apr 2 2026

Mid-upper trough lifts into the Midwest this morning lifting the cold front still lingering over the Ohio Valley back north as a warm front. Elevated portions of this front are now beginning to reach SE MI at time of discussion supporting a broken band of light showers. Showers work northward over the rest of the morning with coverage increasing over the central portions of the state, including over the Saginaw Valley, owing to a lead arm of vorticity reaching west MI. For portions of northern Midland/Bay counties- mainly the higher elevations outside the Saginaw Valley, temperatures hold around freezing for the first couple hours of precipitation maintaining a shot for some lead wintry mix and minor icing up to a light glaze before temps warm to transition to all rain. Given the uncertainty with borderline temperatures and the small areal coverage of the counties, opted not to issue an advisory favoring an as needed short- fused SPS instead. Elsewhere, a few rumbles of thunder within the broader shower activity are possible this morning as elevated theta-e advection into southern lower generates a few hundred J/kg of CAPE. Shower coverage lessens going into the afternoon as warm conveyor isentropic ascent shifts over northern lower/Lake Huron.

Attention then turns to the late afternoon-evening timeframe with the arrival of the surface warm front and prefrontal trough. Likely due to the surface low not reaching WI until ~00Z, there remains good model agreement for a weakly forced/slow moving surface warm front that doesn't reach the southernmost MI counties until ~20Z. Given this model signal and typical climatology this time of year with weakly driven warm fronts, its expected that preceding ESE wind off St Clair and Erie impinge on the front's northward progression over SE MI (which is being picked up in high-res models). This results in SBCAPE residing just to our south and west (as its able to lift more freely over the central/western portions of the state) through the first part of the evening. Anything that manages to initiate off the front in the late afternoon-early evening will struggle to stay rooted in the surface layer as it pushes off the boundary and into SE MI as cooler ESE winds maintain strong 0-1km stability. Main chances for wider spread showers/storms (and outlooked severe potential) arrive latter half of the evening, after ~22-00Z, when a prefrontal trough crosses lower MI. By this point, frontal boundary looks to be buckling into areas west of US-23 as LLJ fully establishes itself over southern lower (45-60kts down to 925mb). As a result, these areas stand the 'best' shot to see a few strong to severe storms with damaging wind gusts around 60mph being the primary threat though given the magnitude of column winds aloft, gusts nearing 70mph can't be ruled out. Mid-level lapse rates aren't particularly impressive, around 6 C/km at best, limiting large (1") hail potential. Hodographs lose low level curvature as the evening goes on, turning unidirectional, confining any tornado chance to the lead line of storms- given favored linear storm mode, this would likely be a QLCS tor type though again, low probability of actual occurrence. For the remainder of the area, height falls associated with the prefrontal trough dislodge and wash the warm front through, however due to occuring around/after sunset, it does not result to a marked response in SBCAPE with instability remaining largely elevated. That said, this elevated instability should be enough to partially maintain storms moving in from the west though probably with a weakening trend further east they get. Additionally the warm front washing through does reduce earlier near-surface stability providing less inhibition for gusts to reach the surface. As such, outlooked Slight Risks have been expanded to encompass nearly all of SE MI. Surface cold front eventually crosses the region late tonight- Friday morning supporting sparser (thunder)shower coverage.

A stronger mid-upper closed low ejecting out over the central Plains Friday induces a downstream height rise response across the Great Lakes stalling the aforementioned cold front either over southern SE MI or northern portions of IN/OH. This trough takes a similar track to today's system placing the CWA again within the warm sector as the stalled boundary lifts back north. Showers and a few thunderstorms are likely Saturday as the low works across the central Great Lakes with its cold front eventually crossing Saturday evening. While kinematics are favorable for severe storms (bulk shear >40kts and SRH >200 m2/s2), sufficient destabilization is uncertain with mid-range models showing a wide spread. Below normal temperatures follow to close out the weekend/start the new work week as 850mb temps fall to -8 to -10C keeping highs generally in the 40s to around 50.

MARINE...

The northeast gradient will increase today as the surface high over Quebec continues to push eastward. At the same time a warm front approaches from the south from low pressure out over the central Plains. This will bring elevated waves into Saginaw Bay and across the Lake Huron shoreline, where Small Craft Advisories are in effect. The low pressure is then forecast to track towards the western Great lakes later today. As the low approaches, easterly winds begin shifting to the south through this evening. There is a low probability for winds to reach gale force late tonight over the far northwestern waters of Lake Huron with gusts not expected to reach the 3 consecutive hour criteria to warrant a headline. Additional low probability chance to reach gales over the Saginaw Bay Friday morning when flow briefly turns southwest (within broader south to west veering). Rain showers will be likely through the morning and into the afternoon along a warm front with increasing chances for showers and thunderstorms later in the day leading into Friday morning. Some isolated thunderstorms may be strong to severe, leading to wind gusts aoa 34 knots.

HYDROLOGY...

Numerous opportunities exist for showers and thunderstorms today through Saturday night. Main windows for potential heavy rainfall are this morning north of I-69, this evening-early tonight across the area, Saturday morning, and Saturday evening across the area. Showers and thunderstorms will be moving quickly, therefore any flooding will be tied to locations that experience the highest frequency of repeat showers/thunderstorms. For today, rainfall totals range from a quarter inch over Metro Detroit to around an inch across the Tri-Cities. The QPF footprint is broader for Saturday with 0.50-0.75 inches expected across Southeast Michigan though some areas nearing 1 inch are possible. Flooding should predominantly be limited to poor drainage and low-lying areas, but the anomalously warm and humid atmosphere could support locally higher rainfall rates that could lead to an increase in flooding concerns. WPC Excessive Rainfall Outlooks place portions of Southeast Michigan within Marginal Risk areas, both days.

PREV DISCUSSION... Issued at 314 AM EDT Thu Apr 2 2026

DTX WATCHES/WARNINGS/ADVISORIES

MI...None.

Lake Huron...Small Craft Advisory until 4 PM EDT Friday for LHZ421-422-441.

Small Craft Advisory until 10 AM EDT Friday for LHZ442-443.

Lake St Clair...None.

Michigan waters of Lake Erie...None.