textproduct: Detroit/Pontiac

KEY MESSAGES

- A continued warming trend brings high temps into the 40s through mid-week with 50s possible Thursday and Friday.

- The next round of widespread rain is expected late Thursday into Thursday night.

- Dynamic low pressure system is forecasted to lift through the region this weekend. Uncertainty exists in heaviest precipitation axis.

AVIATION

IFR to LIFR conditions remain entrenched across the terminals this evening as a surface low crosses southern Lower Michigan. Persistent low-level saturation with weak ascent has ensured a mix of fog and rain/drizzle through the evening hours. A few wet snowflakes could still mix in north of PTK. Conditions will only improve slightly overnight, still holding IFR for most sites into Wednesday morning. Winds reorient westerly behind the departing low which helps usher in slightly less humid air, therefore visibilities are expected to improve prior to ceilings. Did delay the higher visibilities until later on Wednesday given upstream trends at/below MVFR over western Lower, Wisconsin, and Illinois. Ceilings hold in the low MVFR range through most of the daylight hours before lifting above 2 kft AGl and eventually scattering out Wednesday evening as flow backs southwesterly.

For DTW...Predominantly IFR with a brief category change better or worse through the next couple of hours, then lifting to MVFR for most of Wednesday. Precipitation is generally over, but light drizzle (liquid) remains possible.

DTW THRESHOLD PROBABILITIES...

* High for ceiling at or below 5000 feet through Wednesday.

* Low for ceilings and/or visibilities at or below 200 feet and/or 1/2 SM the rest of the evening.

* High in light precipitation type as liquid.

PREV DISCUSSION

Issued at 323 PM EST Tue Jan 6 2026

DISCUSSION...

Cold ground, saturated lower troposphere, and dewpoints in the middle 30s has resulted in widespread dense fog across most of the southern forecast area. Given the breadth of the observations and the low-mid low circulation is not set to reach the eastern cwa border to around 00z, preference was to have a Dense Fog Advisory, I 69 corridor southward, through the evening commute. NWP supports that deeper frontogenesis responsible for widespread precipitation will wane rapidly after 00z as the center of midlevel low pressure circulation passes overhead of the I 69 corridor. There will be some trailing absolute vorticity maxima meridionally from Lake Superior vicinity down to Illinois that will need to advect through the state this evening. Differential cyclonic vorticity advection and a persistence of some convergence is shown to result in some last vestiges of deeper/midlevel deformation late tonight. A low PoP exists late tonight for some potential of drizzle/freezing drizzle or snow shower. No impacts anticipated from precipitation.

Broad split stream ridging will build over the central Great Lakes Wednesday through the first half of Thursday. Forecast soundings show active subsidence occurring around 9.0 kft agl early in the day, with the base of the subsidence lowering to possibly 2.5 kft agl by early evening. The aggressive drying offers an optimism of clearing, but guidance suggests it will be very late (after 20z). Highs in the upper 30s.

Strong potential vorticity anomaly off of the Baja California with arrival of deep troughing in Pacific Northwest Wednesday and Thursday will result in downstream ridge amplification and the development of deep southwesterly return flow across Southeast Michigan. Current indications are that far southern stream PV anomaly will be kicked northeastward with too much separation and little merging through Southeast Michigan. A very warm system, 850mb dewpoints of +8 or +9C. From this vantage point there appears at some potential for neutral stability to instability between 4.0-20.0 kft agl. Convective rainfall possible and elevated thunder may be needed in the forecast Thursday night. Current 75th percentile of the EPS is about .40 to .50 inch. Highs both Thursday and Friday may range in the 40s to 50s.

Ageostrophic circulations developing in response to strong geopotential height falls and changes in upper level jet streak curvature is forecasting a dynamic storm system over the region this weekend. Uncertainty exists due to timing concerns in both vorticity merging and upper level jet phasing. Current data suggests another warm system here locally and that is where the forecast currently resides. Depending on the eventual track of the surface low, strong wind concerns may arise. Bulk of wrap around snow chances looks to be Sunday.

MARINE...

Low pressure lifts toward the southern Lake Huron basin this afternoon-evening. Ongoing precipitation coverage has been greatest north of the system's warm front, which will keep steady rain going into tonight. The more widespread impact of this low has been a blanket of fog across the Great Lakes, which may become locally dense at times this evening. Winds become more uniform by Wednesday morning as the low departs and high pressure fills in. This supports a quieter mid week period before the next string of low pressure systems impact the Great Lakes Friday into this weekend. Initially, warm and stable conditions will prevent an otherwise energetic low level jet from mixing to the surface to keep wind gusts around 30 knots or less.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Dense Fog Advisory until 9 PM EST this evening for MIZ060>063- 068>070-075-076-082-083.

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