textproduct: Detroit/Pontiac

KEY MESSAGES

- Light snow early to mid morning today brings a trace to 0.5 inches of snow to areas north of I 69. Best chance for seeing up to 1 inch of snow is in the northern Thumb region.

- A warmup is forecasted for the middle of the week with temperatures in the mid to upper 30s Wednesday and 40s on Thursday.

- A strong storm system is forecasted to impact the Great Lakes region Thursday and Friday. Much of the precipitation is expected to fall in the form of rain on Thursday, transitioning to snow in some areas Friday. Strong winds will accompany this system as it moves through the region.

AVIATION

Very dry low level air from the northern Ohio Valley will sneak into the southern TAFS allowing the low levels to be ceiling free around taf issuance time. Meanwhile, an elevated warm front will lead to light snow across the northern tafs sites, highest confidence at MBS. Even there, just a dusting expected. Southwest winds increase late this morning through the afternoon with gusts of 25-30 knots expected as clouds scatter out across the south. MBS will continue to be on the edge of MVFR cigs with the Lake Michigan plume. Winds backing around to the west just above the surface and low level cold advection setting back in will allow for low clouds (MVFR) to spread back in from northwest to southeast early this evening, and likely persist through the entire night.

For DTW...Light snow expected to reside north of the terminal this morning, as the low levels will be very dry and likely ceiling free through most or all of the day. Solid mid deck of clouds around this morning however with a flurry possible, scattering out in the afternoon.

DTW THRESHOLD PROBABILITIES...

* Low for cigs aob 5000 feet today, medium this evening, high tonight.

PREV DISCUSSION

Issued at 311 AM EST Mon Dec 15 2025

DISCUSSION...

A plume of shallow, sub 3.5 kft agl thetae advected across portions of Southeast Michigan earlier this evening resulting in large flake flurries. The moisture, which likely had Lake Michigan origins was pooled directly behind the 850-700mb high pressure center and was the initial phase of air mass recovery and warming that will dominate the weather through the beginning and middle of the week. Exit region to upper level speed max and attendant weak Pacific shortwave will push across the northern Great Lakes later this morning as broad ridging and supergeostrophic flow expands eastward. Changing curvature to the jet impulse will provide for weak synoptic lift and a wave of warm advection aloft. Forecast soundings and the forecasted vertical profile of UVV continues to suggest saturation and lift will be very high in the column, upwards of 8.0 kft agl. The tendency of the model data from 24 hours ago suggests that midlevel moisture will becoming increasingly more shallow today as drying will be actively occuring between 12.0 and 16.0 kft agl. Modeled QPF is less in the 12-18Z time window and snow accumulations will be light and inconsequential for most areas. The one exception may be the Thumb where less than one inch is possible. Interestingly, local time-lagged ensemble output for site Port Hope suggests a near 90% probability for 0.5 inch of snow and approximate 40% chance for an inch. NBM 5.0 offers a 55% chance to measure with an approximate 25% for 1 inch in the northern Thumb. Much lesser probabilities exist to the south including in vicinity of Port Huron. No significant changes were needed to the gridded PoP forecast.

Relatively quiet weather is expected Tuesday and into Wednesday with flow evolving more zonal and the height pattern less amplified that what has recently been observed. Models do show a big push to deeper warm air advection arriving Tuesday. Not expecting much impact here across Southeast Michigan as data suggests any light precipitation potential will remain well north of the cwa across Northeast Michigan likely requiring some elevation. Highs Tuesday are expected to rise to the freezing mark. An inflection and corresponding jet streak will support a trough structure through Michigan Wednesday. Deep moisture is significantly lacking but plan views of moisture on isentropic surfaces suggests some low level moisture advecting out of KY/TN northeastward, streamlining ahead of a weak cold front early Wednesday. Forecast soundings showing an extremely shallow depth to the moisture well below the DGZ. Could be looking at some pockets of drizzle or freezing drizzle. The current forecast has temperatures at 32/33F in the 10-13Z Wednesday timeframe.

Models continue to support a deep midlevel trough and dynamic shortwave trough pushing across central/northern Great Plains Thursday. High confidence exists at this vantage point that greatest deformation forcing and cold conveyor processes with mid latitude cyclone will impact portions of Canada, well north of Southeast Michigan. Very high confidence in warm rain precipitation type as model soundings support very warm thermal profile in the lowest 6.0 kft agl with maximum temperature at 850mb of a positive 5-6C. The model trend now suggests that strong wind potential with the system may be a little less than previously thought particularly over Southeast Michigan (still breezy however). The main reason is that the track of the cyclone could verify north of Lake Superior with a much more diffuse surface trough structure extending southward through the cwa. There have been suggestions the cold advection with the front may come in two pieces with the true cold air and best near surface lapse rates well removed to the west of the wind shift. Additionally, nocturnal timing of the cold front would have an impact on downward momentum transfer. Highs Thursday are expected to be in the middle 40s. with highs Friday behind the cold front back into the middle 20s.

MARINE...

We will reside on the northern fringe of an area of high pressure centered over the Ohio Valley today. Winds have turned to the southwest overnight ahead of an approaching trough dropping into the northern Great Lakes. The tightening of the gradient along wit h a strong low level jet passing over the region will lead to winds gusting to around 30 knots though the early part of the day. Low confidence scenerio regarding gale potential today but could see an isolated gust to gale force or two but the window looks fairly narrow late morning into the early afternoon for these higher gusts. Winds will remain elevated through the first half of the week as a series of lows pass near the Great Lakes. Small Craft Advisories are in effect through the day to cover these higher winds and waves. The next system will move in on Tuesday which again is already advertising southwesterly gusts to Gales Tuesday night. Will hold off on another Gale Watch at this time but one may be needed in the next 24 hours if wind gusts remain unchanged.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until 10 PM EST this evening for LHZ421-441.

Small Craft Advisory until 4 PM EST this afternoon for LHZ442-443.

Lake St Clair...Small Craft Advisory from 10 AM this morning to 4 PM EST this afternoon for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 10 AM this morning to 4 PM EST this afternoon for LEZ444.