textproduct: Detroit/Pontiac

KEY MESSAGES

- Accumulating snowfall arrives tonight (mainly north of M-59), but areas north of M-46 could see snowfall accumulations of 1-3 inches. A Winter Weather Advisory begins at Midnight for the Tri Cities and northern Thumb.

- Snow changes over to rain showers Sunday morning with a period of sleet or snow pellets and freezing rain during the transition, mainly along/north of I-69. The Winter Weather Advisory for the Tri Cities and northern Thumb expires at 11 AM.

- Another round of high wind develops Sunday afternoon. A Wind Advisory begins at 11 AM for the area along and south of I-69, including metro Detroit to the Ohio border.

- A line of showers and thunderstorms moves through Lower Mi Sunday night, with some strong to severe storms possible.

- Windy Monday with gusts to 45 mph possible, and also turning much colder with snow showers as temperatures fall from the 50s into the 20s by Monday evening.

- Wind chills minimize around zero Tuesday morning with highs only in the mid to upper 20s.

DISCUSSION

Fleeting influence of high pressure produced a pleasant day by recent standards; highlighted by dry weather, slowly increasing high clouds, and much reduced wind speed. Highs in the mid 30s to around 40 are still a few degrees below normal for mid March.

The increasing high clouds are signs of the next low pressure system and associated round of precipitation already on our doorstep. Mid afternoon satellite, radar, and surface obs show an impressive pattern of virga just south of the IN/OH border that steadily migrates into Lower Mi this evening. One of the forecast challenges is evaluating onset timing as low level saturation occurs while the band continues to move steadily northward. Consensus of 12Z deterministic model runs and HREF mean agree well on a scenario that just grazes metro Detroit with a dusting of snow this evening then increases considerably with northward extent during the late evening and overnight. Forcing evolves from elevated moisture transport into a strong ageostrophic circulation to more of a purely low level jet driven scenario as the low pressure system approaches after midnight. Gradually decreasing stability leads to a burst of higher snowfall rate north of I-69 and eventually a cellular/showery wintry mix as the 50 kt low level drives the warm nose northward. Snow and wintry mix are too brief for a headline along the I-69 corridor. Farther north, the Winter Weather Advisory is in effect for the Tri Cities and northern Thumb where a quick accumulation up to 3 inches occurs with the mix of sleet/pellets and freezing rain toward sunrise. The Advisory is in effect through the morning until surface temperatures rise above freezing.

Precipitation exits northward by noon as the system warm sector builds into Lower Mi and exchanges winter weather for wind gust hazards. The key here is development of a SSW wind direction that neutralizes the Great Lakes stabilizing influence on the boundary layer. A morning to early afternoon time window is available for daytime heating, and this reflected in the development of lower clouds/cumulus in CAM output. Model soundings show this developing as a result of well mixed boundary layer conditions gaining access to the 50+ kt SW low level jet. Surface wind gusts easily reach the 45 mph Wind Advisory threshold, especially by mid afternoon into early evening. There is some uncertainty on how far north of the I- 69 corridor that the full warm sector is able to reach, however it is likely that the Wind Advisory will be expanded in area and extended in time Sunday night and Monday as the deepening low pressure system sweeps a strong cold front across the region.

Prior to the cold front, the warm sector of this system will be firmly rooted across SE Mi. The Advisory worthy SSW wind is projected to help lift high temperatures toward 70 degrees Sunday afternoon from the Ohio border up to the northern suburbs of Detroit. HREF mean produces accompanying surface Td in the mid 50s by Sunday evening to set the stage for thunderstorm concerns Sunday night into Monday morning. The Marginal to Slight Risk is maintained in the Day 2 Convective Outlook for Lower Mi out of respect for the strong wind profile up against lower instability prospects. The system struggles to maintain both surface based and MUCAPE after sunset, and especially after midnight as surface wind projections indicate a tendency to pinch off the low level moisture axis ahead of the cold front. Even so, any surface based convection will have damaging wind potential in the strongly forced environment until the front sweeps eastward Monday morning.

Morning high temperatures near 50 fall rapidly to below freezing Monday afternoon in a return to mid March winter conditions in the Great Lakes. The inbound cold air and strong low pressure forcing set up a lake effect snow shower/squall scenario for the afternoon into Monday evening. Wind Advisory worthy wind gusts continuing through the day enhance the squall potential when combined with mid March daytime instability. The cold air surge then takes temperatures down into the teens and wind chill to near to below zero for the mid week period.

MARINE

High pressure has brought about a brief period of lighter winds, with wind speeds and gusts rapidly ramping up through tomorrow morning and afternoon as an anomalously strong low pressure system travels across the Great Lakes. Low pressure will travel from southern Lake Michigan late tomorrow evening, strengthening as it moves in across northern lower Michigan by Monday morning and afternoon. This initially brings a surge of warm air on Sunday which will produce stable over-lake conditions. Higher stability will reside across the southern Great Lakes where the warmest air enters, which will work to keep gusts just below gales as as strong low level jet enters. Farther north, more neutral low-level profiles will provide better chances for gales starting early Sunday morning. As the low continues to strengthen over the Great Lakes, the pressure gradient will rapidly intensify with cold arctic air then wrapping around the low and into the Great Lakes late Monday into Tuesday. This will then bring the likely chance for gales including some high end gales through Tuesday morning. Gale Warnings are in effect for all of the Great Lakes.

Additionally, prolonged winter weather will be likely with this system. Snow initial moves from south to north across the Great Lakes tomorrow morning, with sleet/freezing rain setting up over north Lake Huron late in the day Sunday, rain to the south. Snow showers, including some embedded snow squalls, are then likely Monday as the arctic air enters.

PREV DISCUSSION

Issued at 1250 PM EDT Sat Mar 14 2026

AVIATION...

Light west-northwest winds becoming variable and shifting to light east-southeast this evening as high pressure slides through southeast Michigan. Mainly high clouds this afternoon before a strengthening warm front lifts north through southeast Michigan tonight. An abrupt start to the snow is expected around or shortly after midnight, starting in the southern TAF sites but quickly lifting north through the rest of the night. The snow band will increase in intensity as it lifts north. Warm air streaming in above the surface will likely support a brief transition to sleet/freezing rain before precipitation ends, as reflected in the MBS TAF. Southeast to south winds will increase Sunday as the warm sector and low-level jet arrive, supporting wind gusts AOA 35 knots by day's end.

For DTW... A period of light snow is likely in the 04Z-07Z window before precipitation lifts north of the terminal. Precipitation could end as a brief period of sleet or light rain. Low clouds should then quickly clear out around 12Z, with southeast to south winds increasing during the day. High confidence in wind gusts exceeding 35 knots late Sunday afternoon.

DTW THRESHOLD PROBABILITIES...

* Low for ceilings aob 5,000 feet tonight and tomorrow.

* Moderate for snow p-type tonight.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Winter Weather Advisory from midnight tonight to 11 AM EDT Sunday for MIZ047>049-053>055.

Wind Advisory from 11 AM Sunday to midnight EDT Sunday night for MIZ060>063-068>070-075-076-082-083.

Lake Huron...Gale Warning from 8 AM Sunday to 4 PM EDT Tuesday for LHZ361-362.

Gale Warning from 8 PM Sunday to 4 PM EDT Tuesday for LHZ363- 441>443-462>464.

Gale Warning from 8 AM Monday to 4 PM EDT Tuesday for LHZ421-422.

Lake St Clair...Gale Watch from Sunday evening through Tuesday afternoon for LCZ460.

Michigan waters of Lake Erie...Gale Watch from Sunday evening through Tuesday afternoon for LEZ444.