textproduct: Detroit/Pontiac

KEY MESSAGES

- A Winter Weather Advisory remains in through this afternoon along and north of I-69 where snowfall totals of 3 to 6 inches are expected.

- All rain or a mix of rain and snow showers occur along and south of M-59 across metro Detroit which change back to all snow by this afternoon.

- Snow tapers off this afternoon followed by colder air leading temperatures down into the teens Thursday morning.

- An active pattern continues late this week into the weekend as arctic air digs in yet again. There is potential for sub-zero wind chill and additional rounds of light accumulating snow.

AVIATION

Snow has changed to all rain at DTW while trending toward a rain/snow mix at PTK and briefly at FNT. Snow is past peak at MBS but remains all snow as low pressure slides west to east about over FNT during the morning. This surface low track keeps MBS at LIFR and FNT at IFR while brining a warm sector MVFR ceiling to DTW with SW wind gusting around 30 knots. Ceiling conditions improve as the trailing band snow moves eastward and wind picks up from the N-NW while passage of the cold front also changes rain back to all snow for any remaining activity this afternoon until exiting eastward late the day. Passage of the low and cold front also bring NW gusts increasing to around 30 knots that last well into this evening post sunset as cold air surges back into the region. A few lake effect cloud streamers make it into SE Mi late tonight but have low predictability into Thursday morning.

For DTW... Light rain continues off and on during the morning and then becomes mixed with and changes back to snow this afternoon. SW develops gusts in the 30 knot range and then shifts N-NW around 18Z through tonight.

DTW THRESHOLD PROBABILITIES...

* High for ceiling at or below 5000 ft through the forecast period.

* High for precipitation type as rain this morning, then high for a transition back to snow after 18Z this afternoon.

* Moderate for exceeding crosswind threshold from 300-330 direction this afternoon.

PREV DISCUSSION

Issued at 358 AM EST Wed Dec 10 2025

DISCUSSION...

Snow spread rapidly across southern Lower Mi since late last evening leading to a peak burst progressing from SW to NE across the area. The heaviest snow is now exiting the M-59 corridor and setting up across the Tri Cities and northern Thumb at forecast issuance. An all snow scenario remains focused there while a mix of rain and snow reaches the I-69 corridor. Snow has or is in the process of changing to all rain south of M-59 across metro Detroit to the Ohio border. These observational trends reflect how effective this low pressure system is at drawing warm air northward to ultimately limit snow accumulation. The Advisory area is then unchanged with this forecast update while monitoring the northern reaches of Midland, Bay, and Huron counties where a short fused Warning upgrade remains possible. The prospects of single digit snow ratio even that far north is the deciding factor for holding off on the upgrade for now.

The system has a very dynamic presentation in satellite and radar imagery making it no wonder that so much warm air is being drawn northward as it tracks roughly along the I-69 corridor during the morning. The rain/snow line set up immediately on the south end of Lake Mi before midnight and has since moved northward/eastward over AZO/BTL to near LAN and PTK at forecast issuance. This matches up well with the surface low track combined with model 1000-850 mb partial thickness that suggest the rain/snow line grazes the I-69 corridor with single digit snow ratio all the way up to M-46. REFS mean soundings show a substantial rain/snow mix up to FNT with support from HREF mean precip type while SREF mean soundings are closer to all snow. At minimum, this supports a sharper single digit snow ratio gradient north of M-46 into about 10:1 ratio toward the northern fringe of the QPF axis across northern Midland, Bay, and Huron counties. The peak snow intensity is definitely Advisory worthy as strong theta-e advection occurs in a steep lapse rate environment to focus high rate snow ahead of the low track where accumulation up to around 6 inches is on target. Totals drop off into the 2 to 4 inch range south of I-69 toward the M-59 corridor where mid level instability is promoting a more cellular character in the pattern leading to a rain/snow shower mix, or just rain showers south of the M-59 corridor after leaving about a 1-2 inch accumulation across metro Detroit since midnight.

Strong SW low level jet forced isentropic ascent supports both the leading pattern of snow while also leading to gusty surface wind driving mild air into region. Surface temperatures surge into the upper 30s on SW gusts in the 30 mph range south of the surface low track to support the full change over to rain. System forcing then transitions to a deformation zone trailing the 500 mb trough and along the cold front this afternoon. This transition has a pivot point just north of Saginaw Bay during the morning and then slides NW to SE across southern Lower Mi. It is aligned along and behind the surface cold front both of which bring a switch back to all snow and about an additional 1 inch of accumulation before exiting into Ontario mid to late this afternoon.

Colder air rushes back into the Great Lakes tonight through Thursday, although with a limited lake effect response still reflected in model data. NW flow around the west flank of the larger mid level trough is shown to generally carry dry air through the mid levels for muted convective depth across the Great Lakes. The colder temperatures end up as the weather highlight as readings drop into the teens by Thursday morning and only recover into the 20s representing the next round of arctic air the just deepens during the late week into the weekend.

MARINE...

Wide spread snow and some rain to the south is ongoing as low pressure tracks across southern Lower Michigan today. The southwest low level jet ahead of the low looks to be very strong (40+ at 925 MB/50+ knots at 850 MB) toward the southern Michigan border. Still a very difficult call on the near lake surface stability over over the nearshore waters of western Lake Erie, as peak south-southwest winds look to be around 12z Wednesday. With the water temp near freezing over the nearshore waters and surface dew pts rising into the low to mid 30s, anticipate just enough limited mixing to keep gusts to gales less than 3 hours, as winds also look to be more southwest/offshore. As usual with offshore flow nearing gales, there will be heighten concern for low water conditions across the western basin of Lake Erie.

Rush of cold air behind the passage of the low in the afternoon will then support strong northerly winds Wednesday afternoon and early Wednesday evening. A gale warming remains in effect, as model data continues to support frequent gusts to marginal gales over most of southern Lake Huron. 850 MB temps lowering to -16 C over northern Lake Huron will promote deep mixing and lake induced troughing, which should keep gusts to gales going over the open waters of Lake Huron, at least through midnight, before winds gradually diminish through the rest of the night into Thursday morning. However, a 500 MB low tracking south along the Ontario/Quebec border will re-enforce the cold air, and should maintain sufficient mixing/gradient over Lake Huron to support gusts in the 25 to 30 knot range out of the northwest during Thursday. Surface ridge building in for Thursday evening/night will lead to much lighter winds, which should linger into Friday as a wave of low pressure track through the Ohio Valley. None-the-less, an Arctic front is on track to move through Friday night, 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.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Winter Weather Advisory until 4 PM EST this afternoon for MIZ047>049-053>055-060>063.

Lake Huron...Small Craft Advisory until 4 AM EST Thursday for LHZ422-443.

Gale Warning from 11 AM this morning to 3 AM EST Thursday for LHZ363-462>464.

Gale Warning from 11 AM this morning to 11 PM EST this evening for LHZ421-441-442.

Lake St Clair...Small Craft Advisory until 4 AM EST Thursday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 4 AM EST Thursday for LEZ444.