textproduct: Detroit/Pontiac

KEY MESSAGES

- Warmer today with a Marginal Risk for severe weather this afternoon, roughly south of I-69. - Below normal temperatures return Sunday and likely persist through mid-week.

UPDATE

Focus for this afternoon and early evening will be thunderstorm development ahead of a cold front that will bring the potential for embedded isolated to scattered severe thunderstorm development. Have trended PoP values higher for this update noting the very well- defined mid-level wave on water vapor imagery along with the potential for late afternoon upper-level support within the left exit region of the approaching jet streak.

Convective mode favors scattered to numerous rain showers with embedded thunderstorms developing along the boundary with a quick evolution to a broken line or line segments. While a brief semi- discrete mode cannot be ruled out initially, the dominate mode will trend towards this broken line/QLCS setup. Most favorable locations for thunderstorms and stronger development will be roughly along a line and south/southeast from Port Sanilac to Hillsdale from 1PM-6PM. Any storm development will move southeast, so locations downstream have increasing chances for rain showers/thunderstorms through the afternoon.

Kinematic fields will be supportive of organized convection with 0-6 km bulk shear values around 40-45 knots, noting the slightly curved and elongated 0-6km segments within the SR-hodographs. Stretched 6-9km segments will bring good storm-top ventilation and will help support updrafts. Buoyancy remains limited but sufficient with modeled SBCAPE/MUCAPE values ranging between 500-1000J/kg, but the stronger low and mid-level lapse rates aid with the buoyancy equation. The primary hazard with any strong to severe thunderstorm development will be damaging wind gusts with any organized line segments/bowing structures. A conditional tornado threat is also possible given any localized enhanced low-level stretching. Large hail (1") will be more conditional. Caveats to the above thinking will be the upstream shower activity across the west half of the state which will usher in high-based clouds, but this overall setup warrants attention through the afternoon.

PREV DISCUSSION

Issued at 657 AM EDT Sat May 9 2026

AVIATION...

Low pressure on a path from the upper Midwest into the northern Great Lakes is pulling mild air into Lower Mi this morning. This has so far produced an area of stratus and fog expanding northward from Indiana on the west flank of departing high clouds. LIFR ceiling and IFR fog along the DTW corridor is reaching northward to PTK and grazes just east of FNT while lifting into the lower MVFR range mid to late morning. This establishes the warm sector ahead of the cold front on schedule to move into the region this afternoon. The front is preceded by a mid level cloud increase and light shower and then a period of thunderstorms mid to late afternoon as the cold front moves through the area. Storms develop overhead from about FNT to PTK and move through the DTW corridor after 18Z until exiting eastward with the front by 00Z this evening. A post front clearing trend looks solid for tonight as well mixed NW wind carries in dry and cooler air. A weak ridge of surface high pressure settles in toward sunrise Sunday.

D21/DTW Convection... A cold front is on schedule to pass across SE Michigan this afternoon. There is increasing potential for a broken cluster/line of thunderstorms to develop nearly overhead as conditions destabilize. An isolated storm could reach severe intensity mainly during the 17Z to 21Z time period.

DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 ft or less this morning, moderate this afternoon, and low tonight.

* Moderate for thunderstorms between 17Z and 21Z today.

PREV DISCUSSION... Issued at 245 AM EDT Sat May 9 2026

DISCUSSION...

Strong shortwave/500 MB height fall center to track through the northern Great Lakes today. Although the height falls struggle to get much farther south than Saginaw Bay, the optimal timing of the cold front/low level convergence during the afternoon hours should be sufficient for numerous showers and scattered thunderstorms. Surface dew pts aoa 50 degrees already noted along/near the southern border. With high temperature reaching around 70 degrees, Sbcape around 1000 J/kg seems likely. With steep mid level lapse rates (700- 500 MB) of 7 C/km and rather strong wind fields (45 knots at 850 MB), isolated severe storms are possible with both wind and hail. Just enough 0-1 KM helicity/bulk shear to suggest a tornado is not totally out of the question before unidirectional low level flow takes over. Far eastern areas, along a Monroe-Detroit-Port Huron line stand the best chance for severe storms, with actually good timing agreement amongst hires solutions (RRFS/ARW/NAM/HRRR) mainly in the 1-5 PM window.

Deep cyclonic flow then develops for the second half of the weekend into early next week, with 850 mb temps progged to bottom out in the -2 to -4 C range Monday morning. Min temps drop into the 30s Sunday night and Monday night; however, there may be just enough wind to help prevent widespread frost/freeze conditions.

The next strong shortwave and associated low pressure system looks to be arriving on Tuesday. Warm front should be active, producing showers as moisture advection is stellar. PW Values start the day on Tuesday around 0.2 inches and surge to 1 inch by early evening. Showalter index stays positive through the day on Tuesday, and just approaches zero Tuesday night, thus not looking for much in the way of thunderstorm activity.

MARINE...

Southwest winds quickly ramping up this morning as a cold front tracks into the Central Great Lakes region. Wind gusts at or above 25 knots are expected near the shorelines this afternoon, along with scattered strong thunderstorms. Thus, small craft advisories have been issued for most of the nearshore waters. The cold front will pass through around 21-00Z early this evening, allowing for winds to shift to the northwest tonight, but under 25 knots over southern Lake Huron and points south.

Another weaker cold front may clip northern Lake Huron Sunday, otherwise a bit quieter as high pressure builds back in with westerly or northwesterly flow persisting into early next week.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until 8 PM EDT this evening for LHZ421-422- 441>443.

Lake St Clair...Small Craft Advisory until 8 PM EDT this evening for LCZ460.

Michigan waters of Lake Erie...None.