textproduct: Detroit/Pontiac

KEY MESSAGES

- Rain showers accompany a cold front tracking north to south today.

- Gusty north wind peaks at 25 to 30 mph this afternoon.

- Lake effect rain/snow showers set up tonight through Saturday. Minor wet snow accumulations are likely across the Thumb, mainly near Saginaw Bay and the Port Huron vicinity.

DTW THRESHOLD PROBABILITIES

* Medium for ceilings at or below 5,000 feet early this morning. High by mid morning and through the afternoon.

* High for p-type as rain through 06z this evening. Medium for a rain-snow mix after 06z.

PREV DISCUSSION

Issued at 406 AM EST Thu Nov 12 2026

DISCUSSION...

Surface low pressure is centered over the Ohio Valley this morning with a trailing hybrid inverted trough/cold front draped northwestward across the Thumb into northern Lower MI. As the low shifts east today, the trough will swing southward across SE MI with synoptic support for ascent from an amplified mid-level shortwave passing overhead. Scattered to numerous rain showers accompany the trough with gusty north to northeast wind (~25-30 mph) ensuing behind it. It will be a rather raw day as temperatures reach the mid 40s but the wind keeps the wind chill near or below 40 F. Cold air advection gains traction tonight with 850 mb temps falling to around -6 C by Friday morning. This will be the driver behind an early lake effect precip event tonight into the late week. Showers will initially be cold rain but transition to mainly melting snow overnight.

Lake effect showers quickly become organized within the cold NNE flow over Lake Huron this evening, with models continuing to advertise two dominant convergent bands - one in the western/central Thumb and one along the eastern shoreline of the Thumb into the Port Huron vicinity. These will be fueled by long fetch over near record warm Lake Huron temps still in the mid 50s F, resulting in sfc-850mb delta-T of nearly 20 C. This contributes to impressive lake induced CAPE of 400 to 700 J/kg with the modified sounding showing convective depth exceeding 10 kft and favorable intersection with the DGZ, indicating efficient snowflake production and high precip rates overnight into midday Friday. The warmth of the lake will end up being a mitigating factor for snow accumulation, especially along the lakeshore where wet bulb temps struggle to fall below the mid 30s. A few miles inland however, the ambient temperature and dew points tenuously near freezing will allow for minor slushy accumulations throughout portions of the Thumb Friday morning. Latest ensemble output continues to target areas downwind of the dominant band in eastern Sanilac and St. Clair Counties for localized amounts up to 1 to 2". Low confidence exists for diabatic cooling within the most vigorous precip rates to lower column temps by a few degrees, leaving the door open for local overachievement in this area.

Daytime Friday will be brisk with wind chill holding in the 30s. Subtle backing to wind direction causes the lake effect bands to shift mainly offshore by late Friday afternoon. However, the immediate eastern shoreline of the Thumb remains a target for additional rain/snow into Friday night. Elsewhere, dry and cold conditions carry temperatures down into the 20s by early Saturday morning. Cool cyclonic flow holds through Saturday but as the thermal trough begins to ease out, any remaining vigor to lake effect ends and temperatures rebound toward the mid 40s. A highly amplified ridge then builds into the Great Lakes Sunday into Monday, offering dry and stable conditions. By Tuesday surface-850mb high pressure reaches the Ohio Valley and burgeoning southwest flow brings a steady warming trend through the middle of the week.

MARINE...

The passage of low pressure across the Ohio Valley this morning will reinforce northeast to north flow across the Great Lakes this week. This will sustain cooler air across the seasonal warmer waters of the Great Lakes, bringing unsettled weather and elevated winds and wave heights. The boost in near surface instability will produce wind gusts ranging between 25 to 30 knots through much of today for most of the eastern Great Lakes. Localized higher gust potential will be found within the Saginaw Bay this morning and afternoon when a brief window for favorable northeast flow sets up. Isolated gust to gales will be possible within this corridor during this time, but confidence remains low that we will see the required 3+ hour time window needed to trigger gale headlines. Small Craft Advisories remain in effect for all nearshore locations.

Wind gusts then decrease slightly tomorrow, but gusts around 20 to 25 knots are still expected to persist across Lake Huron. Widespread to numerous lake effect rain showers are also likely under this setup with the best coverage expected across Lake Huron. An isolated waterspout remains possible with rain shower activity. High pressure to build in on Sunday, relaxing wind speeds and ending lake effect rain chances.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until 10 PM EST Friday for LHZ421-422-441>443.

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

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