textproduct: Detroit/Pontiac

KEY MESSAGES

- A Flood Watch is in effect for southern parts of Southeast MI through early afternoon. Additional rounds of showers and storms are expected through the day and may produce heavy rainfall.

- A Winter Weather Advisory is in effect for the Tri Cities region and northern Thumb this morning due to freezing rain. Ice accumulations of up to 0.10 inch is expected to result in travel impacts early this morning.

- Accumulating snow is likely Friday morning and strong winds in excess of 40 mph are possible during the day Friday.

- Another round of accumulating snow and strong winds is increasingly likely Saturday night through Sunday.

AVIATION

Convectively reinforced surface warm frontal boundary is in place along the Ohio border this morning and has served as a focus for deeper thunderstorm activity. Warm air resides just above the surface and is contributing to a convectively unstable environment above 5.0 kft agl. Models still support a surface low pressure center lifting across far Southeast Michigan this morning in response to greatest upper level jet forcing. Included TEMPO for thunderstorms at the southern taf sites through 15z. IFR and LIFR conditions will then hold until a cold front passes through all of the areas around 17z. Winds turn to the northwest 15 to 25 knots after 17z.

DTW THRESHOLD PROBABILITIES...

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

* Medium for thunderstorms 12-15Z.

PREV DISCUSSION

Issued at 417 AM EDT Wed Mar 11 2026

DISCUSSION...

An earlier line of elevated convection is exiting the area with the stalled surface front now positioned over northwest Ohio. Severe threat through the rest of the early morning is low as the rain- cooled outflow and northeast wind should hold the surface based instability south. 40-50 kt WSW flow noted in kdtx VWP data continues to advect a feed of anomalous moisture into the elevated frontal slope. PWAT analyzed at 1.30" is near the daily max in SPC raob climatology. As the LLJ passes overhead early this morning, expect the flare-up of convection over northern IN to spread northeast across the southern forecast area through midday. Opted to issue a Flood Watch for this area given heavy rainfall already received, weak elevated instability, and increased likelihood for training storms as corfidi vector magnitude falls below 10 kt. Hi- res ensemble data offers 50% confidence for areas to receive over 2" of rain, which is higher than current flash flood guidance. This suggests higher potential for flooding issues in urban areas and along small streams. Areas left out of the watch are not expected to see as much additional rainfall from the next round.

Automated observations overnight indicated intervals of freezing rain across the Saginaw Valley and northern Thumb, with dew points there still holding in the lower 30s. Widespread precip is departing the area but with the additional precip expected later this morning, will keep the Winter Weather Advisory going. It is possible that temperatures and dew points rise comfortably above freezing this morning in which case the advisory may be canceled early.

Additional PVA lifts NE into the area today ahead of the inbound mid- level trough that passes overhead late tonight. The surface low over SW Lower is progged to track NE from to near the St. Clair River by 18z, with the warm sector briefly spreading up into the Metro Detroit vicinity between 15 and 18z. Poor lapse rates near moist adiabatic will limit severe potential but can't rule out isolated gusty winds as the LLJ clips far SE MI. As the low tracks through, backside deformation forcing sustains another round of showers before drier air arrives from the northwest through the afternoon. There may be a couple hour window for light wintry mix as temperatures fall into the 30s from NW to SE. Impacts are not anticipated as any precip will be light. Cooler conditions in the 20s tonight lead into a seasonable day Thursday as upper level confluence within a rising height field sustains mainly dry conditions.

The next northern stream wave arrives Friday morning, amplifying upstream with an impressive corridor of height falls and PVA targeting southern Lower MI. This kicks off deep layer isentropic ascent to produce a quick hitting burst of precip overnight into the Friday morning commute - current timing is lined up between about midnight and 8am. Temps in the upper 20s to lower 30s at onset favor snow initially before warm advection in the low levels brings potential for a changeover to rain by mid-morning. Latest ensemble guidance supports a general 1 to 3 inch wet snowfall mainly along and north of I-69, but possibly into the higher terrain along the glacial ridge as well. Areas farther south are more poised for a dusting.

High confidence exists in a period of strong winds Friday afternoon as the highly dynamic system tracks across the northern Great Lakes. An impressive gradient and strong subsidence/cold advection produce 40+ mph winds and may warrant a headline. The next round of higher impact weather continues to come into focus for the Sunday and Monday period. Guidance has been consistent on depicting a vigorous digging wave inducing strong synoptic ascent directly over the Great Lakes as it takes on a negative tilt. Isentropic ascent ramps up Saturday night to produce a band of snow over Lower MI before the surface low tracks across the area late Sunday. Depending on its track, heavy precip and strong wind will be possible.

MARINE...

Widespread rain and embedded thunderstorms continue today as low pressure tracks along a frontal boundary from southern Lake Michigan toward southern Lake Huron. Cyclonic flow around the low transitions to broader northwest flow tonight that introduces 30+ knot gust potential as cold advection ramps up, albeit brief duration. Active stretch of weather continues for the latter half of the week, with a return to wintry conditions. Increasing confidence in gale potential for Friday as strong low pressure tracks across the Great Lakes, alongside wintry precipitation.

HYDROLOGY...

A Flood Watch is in effect for counties along and south of M-59, as well as southern St. Clair County, through early afternoon. Additional thunderstorms are forecast to track over areas that received heavy rainfall overnight. There is potential for training storms and heavy rates of over 1" per hour to lead to flooding concerns especially within low-lying and urban areas. 50% confidence exists for localized storm total amounts of over 2". Rises on area rivers are expected across Southeast MI over the next few days given the widespread moderate to heavy rainfall since last evening.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Winter Weather Advisory until 10 AM EDT this morning for MIZ047>049- 053-054.

Flood Watch until 2 PM EDT this afternoon for MIZ063-068>070-075- 076-082-083.

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

Small Craft Advisory from 8 PM this evening to 4 PM EDT Thursday for LHZ442-443.

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