textproduct: Detroit/Pontiac

KEY MESSAGES

- Ample sun and very warm today.

- Isolated showers possible Tuesday, becoming wetter with rising thunderstorm potential Tuesday night into Wednesday. The potential exists for severe storms early Wednesday morning.

- Rain showers change over to melting snow showers by Wednesday night with minimal accumulations.

- A clipper system may produce wintry precipitation Friday.

AVIATION

Low pressure passes north of Lake Superior today with Lower MI situated within its warm sector. Daytime heating taps into gusty wind aloft, producing southwest surface wind of 15-20 kt with gusts to 25-30 kt through the morning. As the gradient relaxes this afternoon and evening, wind magnitude will gradually subside. VFR conditions through the day before low-level moisture arrives from the Mid-Mississippi Valley overnight, bringing potential for MVFR ceilings early Tuesday morning. Some drizzle/mist may also accompany this push of moisture mainly after 09z. Meanwhile, a backdoor cold front marked by a northeast wind shift begins advancing southward into the Saginaw Valley and Thumb late tonight with uncertainty on its southward progress by 12z Tuesday.

For DTW...Low confidence in patchy drizzle developing early Tuesday morning, with high confidence in temps well above freezing during this period.

DTW THRESHOLD PROBABILITIES...

* Medium for ceiling at or below 5000 ft after 06z tonight.

PREV DISCUSSION

Issued at 322 AM EDT Mon Mar 9 2026

DISCUSSION...

Straight zonal flow over the northern Plains into Southern Canada today will result in broad southwesterly flow across much of southern Lower Michigan and aid in the development of a stationary front south of the Straits down to Saginaw Bay. Consistent model signal continues with clear skies today and temperatures warming into the middle to upper 60s, approximately 25 degrees above normal. Decent model signal in low level, 925-700mb, thetae advection into Southern Lower Michigan. The moisture advection is expected to both increase clouds tonight and reinforce the stationary front a little farther south, somewhere between I 69 and Saginaw Bay to begin the day Tuesday.

Significant uncertainty exists on potential high temperatures for Tuesday. Question comes down to how aggressive the backdoor marine release will be Monday evening and the prevalence of clouds during the daytime Tuesday. NBM 5.0 25th percentile suggests 40s for the northern third of the cwa and lower to middle 60s south of M 59, whereas the 75th percentile has middle 50s to lower 60s for the Tri Cities/Flint and middle to upper 70s for Metro Detroit. The forecast resides with cooler temperatures near Lake Huron and Saginaw Bay with a northeast wind.

Merging of northern and southern stream upper level jet axes will then force a frontal wave and surface low pressure reflection through Lower Michigan late Tuesday night. There are a number of concerns for the Tuesday night period. 1. Potential for isolated slippery spots due to freezing rain across Midland and Bay counties and far northern Thumb. Tricky forecast with regards to freezing rain potential for portions of Midland, Bay, Saginaw, Tuscola and Huron counties Tues evening/night because of the significant warm air advection that is forecasted to occur. Model soundings show temperatures as warm as 13.5C at 2.7 kft agl providing heat content to the rain droplets. There does appear to be some feedback/contamination of Lake Huron ice cover on surface temperatures immediately downstream of the Lake. There is low confidence that the very shallow subfreezing layer will be able to persist. The forecast continues to reside on the warm side and will need to be monitored.

2. The potential for severe weather early Wednesday morning with likely thunderstorm activity. Differences exist but both the deterministic 3km NAM and the HRDPS support the surface warm front lifting in vicinity of Washtenaw County and Metro Detroit between 07- 12z Wednesday. Forecast soundings support very strong static stability for a greater portion of the forecast area, but neutral stability to convectively unstable conditions will be possible along and south of the front. Will need more CAM data inside of the window to get a better handle on storm mode and potential severe weather threats. At this point, a long hodograph and convective available potential energy to 1000 J/kg suggests strong wind gusts/large hail/and a tornado threat for those areas along and to the south of the warm front. Legit surface low and nose to +50 knot low level jet brings a strongly forced event. The latest Day 2 Outlook issued by SPC has a Slight risk designation for severe weather south and west of a line from Howell to Monroe and Marginal risk for much of the area including, Saginaw, Port Huron and Metro Detroit.

3. Placement of heavy rainfall axis and QPF amounts. With the significant warm air advection and low level jet forcing PWATS are forecasted to reach 1.40 inches Wednesday morning which is at the Daily Maximum for DTX raob data. NBM 5.0 data supports widespread rain with the interquartile range between .75 inch and 1.75 inch with highest amounts across the south. The biggest question is whether or not a favorable corridor will set up for any training convection. Need to get the event window with the CAM solutions but collection of MPAS runs suggests convection will be relatively progressive. WPC has designated all of the area as a Marginal Risk for excessive rainfall.

Composite trough axis and associated absolute vorticity continues height falls into the late Wednesday period. Model data supports a period of deformation forcing that should result in a changeover to snow for the evening period. The potential exists for a minor snow accumulation across Bay and Midland Counties Wednesday evening and melting snow for most areas.

Dynamic Pacific shortwave continues to be advertised for Lower Michigan Friday. Depth of saturation, environmental profile of the front, and projected UVVs through 700-500mb and the DGZ suggests accumulating snow for a portion of the forecast area. PoPs currently reside in the 50 to 70% range.

MARINE...

Southwesterly winds quickly restrengthen early this morning as a second low slides along the far northern shore of Lake Superior. Overall setup is similar to Sunday though with stronger warm advection resulting in more neutral to stable overlake thermal profiles. This further limits sporadic gale potential over central Lake Huron with 25-30kt gusts more likely (20-25kt winds over the rest of the region). A diffuse pressure gradient sets up across the central Great Lakes by late today as the secondary low reaches northern Quebec allowing winds to turn lighter through Tuesday. Active pattern and stronger flow return by midweek as deepening Plains low pressure tracks over the central/southern Great Lakes.

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 0.75-1.75 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...None. Lake Huron...Small Craft Advisory until 4 PM EDT this afternoon for LHZ421.

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