textproduct: Detroit/Pontiac

KEY MESSAGES

- Light snow begins early Tuesday morning, with accumulations ranging from a dusting near the Ohio border to 2 inches in the Thumb.

- Areas of light freezing rain/drizzle possible during the day Tuesday before temperatures rise near the freezing mark Tuesday evening.

- Snow briefly returns Tuesday night before changing over to liquid rain for most of Southeast Michigan; areas along/north of M-46 could maintain all snow leading to accumulations in excess of 3 inches.

- Colder air returns Wednesday evening with a bit of additional light snow possible, followed by the next arctic airmass heading into the weekend.

- Periodic lake effect snow chances exist from Thursday onward.

AVIATION

Dry easterly feed around surface high pressure north of Lake Huron will support gradual deep isentropic downglide through much of tonight. Prevailing VFR conditions are expected through approximately 09-10z. Clipper system will then track into Lower Michigan directing lift and absolute moisture advection across the taf sites primarily in the 10-16z time window Tuesday. Forecast soundings support snow throughout much of the precipitation period with heaviest LIFR activity expected at the northern taf sites. Forecasted moisture profiles suggest that deep moisture will strip out of the midlevels at/after 16z which will bring a potential for freezing drizzle. Very low confidence exists that fzdz will be observed but did maintain the inherited prevailing group at DTW. Could very well be manifested as a br/mist. West winds will then breezy in the afternoon and should keep conditions locked in at MVFR before some potential for ceilings to lower with nocturnal cooling Tuesday night.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling at or below 5000 ft through late tonight. High by Tuesday morning.

* High for initial p-type as snow Tuesday morning before transitioning to a light freezing drizzle/mist midday Tuesday.

PREV DISCUSSION

Issued at 359 PM EST Mon Dec 8 2025

DISCUSSION...

Main focus of this forecast cycle is an active Tuesday-Wednesday stretch as a series of clippers dive toward the Great Lakes/Ohio Valley. The first of these is set to reach SE Michigan during the Tuesday morning commute, with top-down saturation leading to the onset of light snow between 09-12z (4a-7a). It will be a chilly start to the day, with temperatures in the teens and wind chills in the single digits to ensure freezing p-type through majority of the morning hours. Maximum ascent is displaced to our north as the height fall center tracks across nrn MI, with the southern edge of the height fall gradient clipping the Saginaw Valley/Thumb. Areas further south rely on deep isentropic ascent for snowfall production, which ramps up during the morning as system-relative winds veer ahead of the wave. Main limiting factor with this system (as is often the case with clippers), is limited duration of deep column moisture. Slightly longer residence time of deep saturation is expected in closer proximity to the wave (north of I-69), affording a better opportunity for 1-2" of dry/fluffy snow while areas to the south (e.g. Pontiac/Detroit/Ann Arbor) are held to an inch or less by mid-day Tuesday. Even though overall storm totals do not reach advisory thresholds, timing of peak snowfall rates (5a-9a) will occur during the morning commute and will create variable road conditions and slick spots.

The short duration of deep saturation is attributed to the arrival of a mid-level dry slot, which strips away moisture from the DGZ and leaves a shallow ~5.0 kft cloud layer that could generate a few hours of freezing mist/drizzle mid-day. This comes as temperatures are warming and ice nucleation becomes less likely aloft. Precip gradually tapers off through the early afternoon with temperatures climbing into the upper 20s by noon. Warming temperatures afford better mixing of the boundary layer to tap into a ~35-40 knot LLJ, resulting in a breezy afternoon. Southwest gusts of 25-30 mph will be possible to keep wind chills in the teens for most of the day.

Immediately behind this wave is another clipper system, although with a more organized circulation in terms of both magnitude and depth. This wave carves toward the Ohio Valley late Tuesday evening, with light snow returning to SE Michigan after about 03z (10p Tue night). With the low tracking along a more southerly path, its warm front is able to pivot into Lower Michigan overnight and gradually raise temperatures into the low-mid 30s by Wednesday morning. Fairly sharp gradient in snow accumulations exists across SE Michigan as a result, with the 32 degree isotherm generally holding right along the M-46 corridor (coincident with the forecast track of the surface low). This low (and the freezing line) however have both trended south in recent forecast cycles. Main implication of this is that forecast temperatures are trending colder, and snow totals are increasing especially across nrn portions of the cwa. The current forecast calls for 4-6" of wet snow north of M-46, with tapering accumulations to below 1" near the Ohio border where temperatures may be aoa freezing at precipitation onset. Pending any dramatic northward shifts in the track, advisories will likely be needed across nrn portions of the cwa. Not entirely out of the question to reach entry level warning criteria either in the far north, especially along/north of the surface low where banded structures will be possible in the focused ascent regions of the frontal zone. This outcome looks more likely over nrn Lower Mi at this time, precluding any watch issuances with this forecast cycle.

Snowfall tapers off through the day Wednesday as the system drifts into Ontario and its cold front settles into Lower Michigan. Shift to north-northwest flow looks to activate Lake Huron/Lake Michigan, which may provide a window for Lake Huron bands to impact the shoreline counties Wed night-Thu morning. As usual, this will be highly sensitive to wind direction. High pressure briefly fills in Friday, but the wave train remains active with signs for additional snow and cold lingering into the weekend.

MARINE...

Light and variable winds around this afternoon as high pressure remains over the area. However, a quick ramp up in south-southwest winds this evening and tonight as low pressure tracks through Lake Superior, dragging a warm front through the Central Great Lakes. Wind gusts look to reach at least 30 knots across all marine waters, with brief gales even possible in the 12-15z Tuesday time frame. Small craft advisories will be issued with this forecast package, and will be carried right through Wednesday as well. A larger and stronger low pressure system is then on track to move through Lower Michigan Tuesday night into Wednesday producing widespread snow and even rain over Lake St. Clair and Lake Erie. The southwest low level jet ahead of the looks to be very strong, and low level profiles may not warm quick enough to stabilize the near water surface. Thus, it is looking like a short period of gales will occur over western Lake Erie, with even brief isolated gusts to gales over Lake St. Clair. On the flip side, with the water temp near freezing and a downward trend in model wind speeds at the surface, elected to hold on off on gale watch. 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 will then support strong northwest winds Wednesday afternoon and early Wednesday evening. Isolated, brief gusts to gales remain likely, but the cold advection is exhausted quickly and the pressure gradient relaxes by Thursday morning. With the short duration and the marginal nature of the gales, elected not to issue gale watch and just have the small craft advisories carry right into Wednesday night. The cold airmass (850 MB temps in the negative lower teens/around -10 C) looks to persist to close our the work week, supporting moderate winds and scattered snow showers.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory from 4 AM Tuesday to 4 AM EST Thursday for LHZ421-422-441>443.

Lake St Clair...Small Craft Advisory from 7 AM Tuesday to 4 AM EST Thursday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 7 AM Tuesday to 4 AM EST Thursday for LEZ444.