textproduct: Detroit/Pontiac

KEY MESSAGES

- Isolated showers possible today, becoming wetter with rising thunderstorm potential tonight into Wednesday. The potential exists for severe storms this evening and early Wednesday morning.

- Winter Weather Advisory is in effect for the Tri Cities region and northern Thumb from this evening until late Wednesday morning. Ice accumulations of up to 0.10 inch is expected to result in travel impacts Wednesday morning.

- Rain showers continue Wednesday with brief change over to melting snow showers by Wednesday night possible.

- Accumulating snow is likely Friday with a dynamic clipper system tracking through the Great Lakes. Strong west winds in excess of 40 mph may be possible during the daytime Friday.

- Another strong low pressure system may impact the Great Lakes to start next week.

AVIATION

Warm, moist flow arriving from the southwest rides over a backdoor cold front sinking south across the area today. This produces widespread MVFR to IFR ceilings and spotty showers at times through the day, with a rumble of thunder also possible. Highest probability for IFR occurs through this morning and again tonight. The front crosses the Metro Detroit vicinity by late afternoon before stalling near the state line this evening. This will be marked by a surface wind shift to northeast. The stalled front and a LLJ arriving late this evening will generate several rounds of convection tonight into Wednesday morning; some storms may be severe and produce heavy rainfall. Cold wind off Lake Huron will support a period of freezing rain for the Thumb and Saginaw Valley, and did introduce into the TAF at MBS. Surface low pressure tracks from northern IL along the front and across southern MI between 10z and 14z Wed, with continued MVFR to IFR conditions and a transition to all rain likely for MBS.

For DTW...Low chance for a rumble of thunder through the daylight period. Fropa timing carries some uncertainty but is generally targeted between 20 and 00z with northeast wind around 10 kt through this evening. Numerous showers and thunderstorms in the vicinity 01z tonight to 18z Wed. Wind direction will carry sensitivity to position of the stalled front in the vicinity.

DTW THRESHOLD PROBABILITIES...

* High for ceilings at or below 5000 feet through the forecast.

* Low for thunderstorms today. High between 03 and 09z tonight. Medium 09z to 15z Wednesday.

PREV DISCUSSION

Issued at 412 AM EDT Tue Mar 10 2026

DISCUSSION...

Northern and southern stream jet streak merger begins this afternoon over the Mid Mississippi and southern Great Lakes region kicking off an ageostrophic response sharpening what is already a baroclinic environment. Multiple waves/episodes of warm air thetae advection into Lower Michigan will conclude with a significant wave of low pressure along the stationary front Wednesday. There are a number of items to discuss and will refer to them by the expected time window of occurrence.

Early today. Evening marine release has the surface based frontal zone backdoored in place between Flint and Saginaw. Surface dewpoints to the north of the front reside in the lower to middle 30s. Increasing clouds today (limiting insolation), possible light precipitation (wet bulb impacts), and compacting of mslp gradient is expected to cause the frontal zone to slip southward during the midday timeframe.

21-03z South. Various hires solutions, HRRR and MPAS solution support isolated-scattered thunderstorm activity tracking out of Illinois through northern Indiana later today towards Lower Michigan this evening. Models suggest that there will be the potential for organized convection to impact the far southern counties. Question becomes whether or not convection is surface based here in Southeast Michigan as the potential exists for a rain cooled near surface air mass and another evening marine release to suppress the surface warm front to south of the border. Both the HRRR and NAM suggest this is a possibility, although both then support the boundary lifting back northward ahead of the main surface low at 15Z Wednesday. SPC has expanded the the latest Slight risk in SWODY1 to the north to include all of Metro Detroit and the tornado Conditional Intensity Group 1 to the south of Detroit. The most likely time window for potential severe weather may be 00-05z and again 09-12z (discussed below). All hazards will be possible based on lengthening hodograph and helicity values in excess of 400 m2/s2.

00-06z North. Consensus of guidance, including NBM 5.0 FRAM, HREF 3hr FRAM accretion data, and local in-house probabilistic data all support freezing rain activity for the Tri Cities and northern Thumb this evening and tonight. Issued a Winter Weather Advisory for freezing rain and up to a tenth of an inch icing that is expected to impact travel. Based on forecast soundings for KMBS which are overwhelmingly cold in the lowest 1.5 kft agl decided to include Saginaw County in the Advisory. Perusing the data, heavy rainfall rates and convection should lead to greater wet bulb cooling with a cold northeast wind off of Lake Huron. The other consideration here is that winds of 30- 35 mph will be possible off of the Bay. Limiting factors for the event may be a warm ground (68 degrees yesterday) and warm rain droplets (11C at 3.0 kft agl).

09-12z South. The first surface low reflection potentially augmented by MCV dynamics is expected to track invof I 94 corridor. Difficult to offer much confidence in the surface stability here locally. The nam continues to suggest lower 60 dewpoints and potentially 1500 J/kg of CAPE will lift across the Ohio border towards Detroit ahead of 12Z. Will definitely need to be monitored as heart of 60 knot low level jet will push across at the same time frame. Severe weather appears possible.

Storm total Precipitation amounts and QPF. NBM 5.0 QMD data highlights the 25th percentile between .5 to 1.25 inches rain with the 75th percentile between 1.25 to 2.00 inches. Current guidance supports highest rainfall amounts across the southern cwa. There is a hires signal that suggests multiple rounds of convection south of I 96 could result in some urban heavy rainfall issues. Day 1 Excessive Rainfall Outlook is expected to have Marginal for all of Southeast Michigan with a Slight risk extending into Lenawee County.

Exit region to very strong Pacific jet core is forecasted to dig through the Great Lakes Friday. All signs point to an amplifying and dynamic low pressure system. There are differences that exist in the models regarding in the exact north to south track of the absolute vorticity maximum. The exact path is expected to have a definite impact on snowfall amounts. Will need hiresolution nwp in the time horizon but a couple/few inches of snow may be possible for a portion of the area. The big thing to add for the Friday system is favorable timing of steepening lapse rates due to cold air advection in the background of strong mslp gradient may lead to wind gusts in excess of 40 mph during the daytime Friday.

Data still suggests a powerful mid latitude cyclone will be possible for the Great Lakes region at the end of the upcoming weekend. Much below normal temperatures early next week.

MARINE...

The pressure gradient sharpens today across the Huron basin, ahead of a more active stretch of weather tonight into Wednesday. Non- thunderstorm wind gusts may approach 30 knots for Huron late tonight into Wednesday as low pressure, 29.50 inches, lifts across Lower Michigan. A Small Craft Advisory is in effect for higher waves this afternoon into Wednesday afternoon for the ice-free nearshores (Outer Bay and the tip of The Thumb). Expect several rounds of showers and thunderstorms with the low, including some strong to severe storms. All severe hazards will be possible. The system's frontal passage eventually leads to cold advection, a transition to melting snowfall, and steep low-level lapse rates which translates to more efficient mixing. Low-end gale potential exists Wednesday night. Seasonably cool conditions ensue Thursday, followed by more rain, snow, and wind with another system on Friday. A stronger wind field may support a period of widespread gusts to gales.

HYDROLOGY...

Widespread showers and thunderstorms will develop Tuesday night into Wednesday as a low pressure system tracks northeastward across Lower Michigan. Expected rainfall totals range from 0.75-2.00 inches by Wednesday evening, followed by a changeover to melting snow from north to south. Ensemble data suggests rises on area rivers will be expected with a chance for minor flood stage for river systems.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Winter Weather Advisory from 8 PM this evening to 10 AM EDT Wednesday for MIZ047>049-053-054.

Lake Huron...Small Craft Advisory from 4 PM this afternoon to 4 PM EDT Wednesday for LHZ421-441.

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