textproduct: Detroit/Pontiac

KEY MESSAGES

- Arctic air will impact the region Saturday into Monday, featuring well below normal temperatures. Wind chills will be in the single digits to sub zero.

- The coldest period will be Saturday night and Sunday morning when wind chill readings will drop to 5 to 15 degrees below zero.

- Warmer temperatures are forecast Wednesday into Thursday of next week.

DISCUSSION

An overall backing of the low level flow toward the west and a lowering of the inversion will allow a decrease in the coverage of snow showers and flurries this evening. There is likely to be good deal of strato cu through the night trapped under the low level inversion. This should hold min temps largely in the teens despite the resident cold airmass. The potential for a few breaks in the Saginaw Valley/Thumb will warrant a little colder temps in this region. A low amplitude short wave is still forecast to traverse the Ohio Valley tonight and Friday, with the associated snowfall well south of the forecast area. Broad mid level subsidence through both confluence and weak negative vorticity advection will maintain a dry forecast across Se Mi Friday. Even with some potential breaks in strato cu field, cold air locked in place will hold highs in the mid/upper 20s.

An approaching upper low from the northwest will spread mid level height falls across Lower Mi Friday evening. A narrow axis of mid level moisture in advance of the upper low will support a brief period of respectable lake effect off Lake Michigan. A backing of the low level flow from southwest to west Friday evening will drive some of the lake effect into Se Mi, enhanced by the period of large scale ascent and deep layer moisture. The duration of light snow or any potential heavier bursts of snow showers which release off Lake Michigan will be brief, which will keep total snow accumulations minimal. Model blended solutions suggest snowfall amounts of a dusting to half inch. Even the 90th percentile has total accums of just an inch. This lends to support to high probabilities for snow, with low QPF/snow accum potential.

As the upper low tracks across the northern lakes Saturday/Saturday night, forecast amplification within the larger scale trough will drive an early season blast of extremely cold arctic air into the region. 850mb temps are forecast to plunge toward -20C Saturday afternoon, with the extreme cold holding over the region into Monday. Daytime highs will largely be in the teens to near 20 with nighttime lows in the single digits. The cold air advection on Saturday and the lake aggregate troughing on Sunday will maintain some elevated wind speeds through the weekend, with gusts over 25 MPH at times. This will result in some sub zero wind chill readings, especially during the morning hours. While the moisture flux off the lakes will support some lake effect, limited inversion heights and the very dry and cold arctic airmass suggest that mainly some flurries may make their way into Se Mi this weekend. A pattern shift next week continues to offer high probabilities for a warming trend Wednesday into Thursday, with highs possibly into the 40s.

MARINE

Elongated area of high pressure is over the region today, wedged in between a strong low over the far northeast conus and second area of low pressure developing over the western Plains. The resultant northwesterly gradient will remain elevated due to cold air filtering into the area but below gale force with the lack of stronger gradient support. Small Craft Advisories continue through this evening to account for elevated wave heights from the persistent northwesterly flow. Winds will remain lower into Friday before the next clipper tracks through Ontario Friday night into Saturday, pulling an arctic front through the region Friday night. This cold airmass will again bring increased winds with sporadic gusts to gales possible over Lake Huron during the weekend as 850 MB temps plummet to -20 C, supporting snow squalls and freezing spray as well. Another round of Small Craft Advisories seem likely at a minimum through the weekend.

PREV DISCUSSION

Issued at 106 PM EST Thu Dec 11 2025

AVIATION...

West surface flow with northwest flow aloft will continue to advect lake moisture inland, maintaining an extensive strato-cu field along with flurries through daylight hours. Confidence regarding cloud trends wane overnight as wind streamlines divert from pure west- northwest flow, hampering lake moisture advection. The current thinking is that stratus continues to hold overnight under an inversion, with lower end probabilities for mvfr cigs as cloud bases sink. A much lower confidence scenario will be the scouring out of cloud cover overnight which would then introduce chances of some freezing fog potential leading to visibility restrictions. The former has been representing in the ongoing TAFs given the higher confidence of the maintenance of the stratus deck.

For DTW...Mainly VFR ceilings with flurries. Brief MVFR drops possible. Max westerly gusts to 20 this afternoon and early evening.

DTW THRESHOLD PROBABILITIES...

* to high for ceiling at or below 5000 ft through this afternoon, moderate this evening and overnight.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until 10 PM EST this evening for LHZ421-442.

Small Craft Advisory until 4 AM EST Friday for LHZ441.

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