textproduct: Detroit/Pontiac

KEY MESSAGES

- Widespread showers and some embedded thunderstorms are expected through the day Saturday.

- Below normal temperatures return Sunday and through early next week.

UPDATE

The forecast was updated to include wind gusts of at least 35 mph, as the frontal passage (FROPA) and strong low-level winds (near 50 knots at 925 mb per 12z DTX raob) support this higher gust potential. While 925-850 mb wind fields will gradually subside, facilitating solar-aided mixing will help boost mixing depths. A sharp temperature contrast currently exists across southern Lower Michigan, ranging from the upper 30s in the west to near 70 degrees in the east. Robust low-level cold advection is making for a difficult hourly temperature trend, as most daily maximums have already occurred. However, a modest secondary rise is expected this afternoon with partial April insolation.

A potent 50-60 kt southwest low-level jet (LLJ) will begin its northward surge out of the Plains tonight. This will initiate an excellent moisture surge, with PW values ramping up from roughly 0.40 inches this afternoon to a staggering 1.30 inches by 12Z Saturday. This represents a 2-3 standard deviation anomaly for early April, suggesting highly efficient rain-producing processes tonight into Saturday morning. Fortunately, instability and mid-level lapse rates remain weak; no surface-based instability is expected through tonight as surface winds remain backed out of the southeast.

Into tomorrow, the severe threat remains notably low despite the robust moisture. A persistent near-surface inversion will be maintained by the combination of early-morning rain and thick cloud cover as the occlusion resides over Southeast Michigan for most of the day. There appears to be a short window during the afternoondepending on the track and intensity of the low through northern Lower Michiganwhere eastern areas could enter a muddled warm sector before the cold front swings through by early evening. Strong wind fields (50 knots at 850 mb) could still support a marginal wind threat, even with the weak surface-based instability. Will take longer and more detailed look for the afternoon package.

PREV DISCUSSION

Issued at 502 AM EDT Fri Apr 3 2026

AVIATION...

Cold front on pace to clear the area by late morning. Period of modest low level cold air advection within the immediate wake will maintain a higher coverage of MVFR stratus into midday. Clearing potential increases from south to north this afternoon under steady diurnal drying/mixing in gusty post-frontal westerly wind. Gusts intermittently into the 25 to 30 knot range today. Easterly flow develops tonight as deeper moisture surges back northward along an advancing elevated warm front. This will translate into a high coverage of showers, with sufficient mid level destabilization to support embedded thunderstorms during the early morning hours. Greater near surface saturation likely immediately ahead of the surface warm front, offering a window for possible IFR to LIFR conditions Saturday morning.

DTW THRESHOLD PROBABILITIES...

* High for ceiling at or below 5000 ft this morning. Low this afternoon and evening. High again tonight.

* Moderate for thunderstorms overnight. Low Saturday.

PREV DISCUSSION... Issued at 335 AM EDT Fri Apr 3 2026

DISCUSSION...

Low pressure system to depart from northern lower Michigan into eastern Ontario and western Quebec late this morning into the early afternoon hours. Weakly cyclonic flow will set up a baroclinic zone over Michigan by the afternoon which will produce a moderate temperature gradient across SE MI. Locations along and close to the MI/OH border and up through the Metro region will see temperatures rise through the 60s, possibly up through the northern Metro region through Port Huron. Stratus now filling in across a greater portion of the cwa and moderate temperature highs into the afternoon until daylight works to scour out the better coverage. Temperatures highs in the 50s likely hold across the northern third of the cwa. Neutral profiles this morning stay shallow but better mixed through the late morning to early afternoon hours bringing wind gusts of 25-30 mph, isl 35.

A second low pressure system to develop across the central Rockies this morning which will gradually strengthen while pushing into northern lower Michigan by Saturday. Shallow isentropic ascent will commence tomorrow morning which will bring increasing chances for showers with some isolated thunderstorm potential from south to north. Progression of the low into Michigan with a strong mid-level wind field on the southeastern flank of the low will efficiently advect in Gulf moisture through SE MI with pw values reaching around 1.30 inches. Widespread rain is expected with the high moisture content as forcing ahead and along of a cold front helps sustain rain chances through the afternoon and evening hours. Position of the low along with early morning rain and cloud cover does not look to afford a window for destabilization across SE MI, noted with mean HREF SBCAPE struggling to peak past 100 J/kg. Overall kinematics look poor with only a small window ahead of the cold front where 1-3km bulk shear vectors near 25 to 30 knots, with unfavorable vector orientation relative to storm motion. Thus overall the severe threat remains low at this time.

Departure of the low brings cooler temperatures back into the Great Lakes by Sunday morning with lows dropping into the 30s and high capped in the 40s. The thermal trough will become reinforced Monday into Tuesday with a shortwave carving into the greater trough. Passage of the wave brings the chance for wintry precipitation Monday morning and afternoon. Highs do make it into the 40s by the afternoon hours but very steep low level lapse rates produce a low freezing level bringing the chance for a rain/snow mix or melting snowflakes. Some elevated weak instability also brings chances for some more convective based activity that can produce graupel. A strong high pressure is then expected to build in by Tuesday, bringing dry weather with the continuation of below normal temperatures.

MARINE...

A low pressure system crossing northern Lake Huron will drag a cold front across the central Great Lakes today. Southerly winds decrease and veer westerly behind the cold frontal passage, which eventually leads to decreasing wave heights. Small Craft Advisories drop-off accordingly throughout the day for Saginaw Bay and southern Lake Huron. Drier conditions are expected through the daylight hours before unsettled weather returns Friday night. The next warm front slowly lifts into the southern waterways aloft, well ahead of the surface boundary, triggering some nocturnal showers and perhaps a few thunderstorms. The associated trailing surface low should reach southern Lake Michigan by Saturday morning as the elevated warm front continues to track northward across Lake Huron. Some strong to marginally severe thunderstorms should affect the waterways late tonight and Saturday morning, before one final round develops Saturday evening with the passage of its cold front. The main threat will be strong gusty winds in excess of 34 knots and half inch hail.

HYDROLOGY...

Rain showers with embedded thunderstorms are expected early Saturday morning with likely chances continuing through the day. Total rainfall accumulation will range between a half-inch to an inch by Saturday night. Widespread rainfall will cause rises on area rivers and bring potential to reach flood stage, with highest confidence across the Saginaw Valley. River crests are forecast to occur this weekend.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until 4 PM EDT this afternoon for LHZ421-422- 441>443.

Lake St Clair...Small Craft Advisory until 4 PM EDT this afternoon for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 4 PM EDT this afternoon for LEZ444.