textproduct: Detroit/Pontiac

KEY MESSAGES

- Light rain showers/drizzle are possible tonight mainly south of M-59. Some freezing drizzle possible in the higher terrain of Oakland, Washtenaw, and Lenawee. Little to no ice accumulation.

- Widespread freezing rain and wintry mix for much of Southeast Michigan Friday. Ice accumulations of a tenth or two favored though some locales could approach a quarter inch. An inch of two of snow possible in the northernmost portions of the Thumb.

- Arctic cold front late Sunday with strong northwest winds appearing likely Sunday night and Monday.

AVIATION

Low pressure slides quickly through the Ohio valley while grazing southern Lower Mi tonight. Thick mid level clouds show virga indications on radar while precipitation reaching the ground is confined to near the Ohio border, and even there only trace amounts are expected. The bulk of MVFR ceiling associated with this system also slides south of the area leaving greater potential for ceiling restriction tied to low level wind veering toward the NE during Christmas morning. Coverage of stratus already observed in the northern Great Lakes is enhanced as colder air activates Lake Huron while wind speed increases into the 10 to 20 knot range across SE Mi during the afternoon into Christmas night.

For DTW... There remains a brief chance of light rain/drizzle tonight /04z-08z/. Some patches of freezing drizzle are plausible as temperature hovers near freezing. The low predictability of brief and light occurrence prevents a forecast mention in this update.

DTW THRESHOLD PROBABILITIES...

* Moderate for ceiling 5000 feet or less late tonight and Christmas morning.

* Very low for precip type as freezing drizzle late tonight.

PREV DISCUSSION

Issued at 329 PM EST Wed Dec 24 2025

DISCUSSION...

Strong stability and dry air influence provided by a compact area of surface high pressure will continue for the next 6 to 9 hours. Very quiet weather is expected for much of the evening with temperatures easing down to the freezing mark after nightfall.

Late evening and tonight, weakly phased upper level jet streak/dynamics and shortwave energy cresting the ridge out of Minnesota will provide for moisture/saturation below 7.0 kft agl. Forecast soundings are certainly interesting in December with the 850-300mb lapse rates. Guidance has been suggesting a convective component to the tonight period to the south and west of the area. Given the lack of midlevel moisture could be looking at more of a drizzle or light shower character here locally. Preference is to side with a warmer precipitation type particularly for the city of Detroit with freezing heights at 8.0 kft agl and a max temperature in the column of 7C. There is a non zero potential for freezing drizzle, especially in the Irish Hills of Lenawee/Washtenaw/Livingston/Oakland counties overnight but an extremely short duration is expected to limit any impacts if it were to develop.

The Global Deterministics remain in good agreement that a wave of low pressure/surface reflection will eject flatly through portions of northern Indiana/Ohio Friday. A well defined, anticyclonically curved H3 jet exit region is forecasted to provide for an ageostrophic response with favorable 925-850mb, 850-700mb frontogenesis over Southeast Michigan after 12Z Fri. The first order forecast problem for the Friday system has evolved in a big way from a thermal question to one of QPF distribution and liquid equivalent amounts. The ECMWF, GFS and now RGEM control runs have been and remain in very good agreement on a hearty QPF axis (24 hrs values at or well above 0.50") through central to northern portions of the cwa. In contrast, the hires convection allowing CAMs suggest a significantly more southern solution (potentially south of Metro Detroit and the Michigan state line). The reason for the more southern CAMS solution appears tied to a convective release occurring lower down the frontal slope immediately southwest or south of the cwa. There are signs QPF could favor the 900-825mb frontal layer near Ohio/MI stateline to Lake Erie but where exactly the greatest precipitation rates occur has now become the forecast problem. Not shockingly, these same CAMS are casting doubt on the quality of moisture/saturation above 700mb across much of Lower Michigan. For reference, the NAM12 and 24.12z 3km NAM struggle to generate 0.10 of liquid equivalent north of the I 94 corridor. Even with a sharper lower tropospheric frontal surface south of Detroit, models do support a period of 290-306Ks system relative isentropic ascent over Southeast Michigan between 15-21z. One last item that will eventually need consideration is the potential for sleet to eat into freezing rain and icing mounts. Models continue the recent trend for a colder solution, with many locations now expected to remain below freezing. Given the incredible QPF and liquid equivalent uncertainty, the more desirable approach this forecast package was to continue widespread freezing rain with icing amounts of 0.10 to 0.20 inch and message widespread impacts to travel Friday morning/afternoon. For the northern Thumb and Huron county, snowfall is anticipated with 1 to 3 inches currently forecasted, again conditional to liquid equivalent. Hopefully, predictability with this system will increase.

High amplitude, record breaking upper level ridge is forecasted to finally push across Southeast Michigan on Saturday. Anomalously strong inversion is anticipated with 850mb temperatures of +9C at 850mb. Raw model guidance appears to be too cold given the warm air aloft, but dry conditions are in store Saturday. The next dynamic system is then set for Sunday. To make it brief, there is reasonable high confidence in QPF falling in the form of rain before the cold front. The big forecast item to monitor late Sunday, Sunday Night and/or Monday is strong synoptic scale wind potential which may necessitate wind headlines per forecasted mslp gradient. Much colder weather to follow for the beginning of next week with inland penetrating lake effect/snow squall potential.

MARINE...

The high pressure system currently bringing lighter winds will continue to push away from the Great Lakes region as a second high pressure system moves eastward across the James Bay region overnight. As the second high pressure system pushes eastward, northeast flow overnight will shift to the southeast on Thursday and increase in speed by the afternoon. This will bring elevated wave heights along the Lake Huron shoreline. Small Craft Advisories may be needed Thursday into Friday given the favorable fetch increasing wave heights. The shift to east flow overnight Thursday will also bring some stronger gusts with wind gusts ranging between 20 to 30 knots across Lake Huron. Easterly flow will persist through Friday as a low pressure system brings in wintry precipitation to the region.

DTX WATCHES/WARNINGS/ADVISORIES

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