textproduct: Detroit/Pontiac

KEY MESSAGES

- A strong storm system will impact the Great Lakes today into Monday, bringing a wide array of weather concerns to southeast Michigan.

- Rain will affect the region today, with some periods of heavier showers and thunderstorms possible. There is a slight chance for strong thunderstorms this evening.

- Wind gusts of 50 to possibly 60 MPH are forecast tonight through Monday as much colder air infiltrates the region. A high wind watch remains in effect for these winds.

- Snow showers/snow squalls are forecast Monday. Snow accumulations less than 2 inches is expected, however these will pose for hazardous driving conditions.

- Seasonally cold conditions with wind chills in the single digits and teens will occur Monday through the end of the week.

DISCUSSION

The main focus of this forecast cycle will be the storm system set to impact the Great Lakes today through Monday. Ongoing amplification of the mid level wave diving across the northern high plains will drive the low pressure system over Kansas into nrn Illinois by late afternoon. Phasing of an upper jet streak diving southward along the western flank of this wave with a 140kt upper jet lifting out of the southern Rockies and strong baroclinicity across the Great Lakes will result in rapid deepening of the compact mid level low and the associated surface low as it lifts into Lake Huron tonight on its way to southern Quebec by Monday evening. There remains some spread among the 00Z model suite and their ensemble members as to the rate of deepening of the sfc low as it tracks across the region. The deterministic GFS is on the stronger side of the 00Z operational suite, indicating a 995mb low near Chicago at 21Z deepening to 975mb over far northern Lake Huron by 12Z Monday morning. There are several other solutions which indicate a 980mb low Monday morning, with the latest ECMWF at 978mb. These subtle differences will largely impact the strength of the peak wind gusts tonight/Monday.

Intensifying low level southwest flow within the developing warm conveyor will drive extremely warm and moist air into Se Mi for late December. Precipitable water values are forecast to rise 1.1 to 1.3 inches, around record values for Dec 28th. The initial surge in moisture advection this morning will result in light rain across the area. Some lingering sub freezing sfc temps may support a brief period of freezing rain (mainly north of the I-94 corridor) before temps rise above freezing. Enhanced low to mid level frontogenesis along a slow northward advancing warm front will set up a near quasi stationary band of enhanced west to east forcing this afternoon, coinciding with the strongest moisture surge and developing elevated instability. This will result in an axis of more frequent and heavier showers and thunderstorms embedded within the broader region of light rain across Se Mi. An inch or more of rainfall appears likely within this band. There is model spread as to where within the CWA this axis of heavier precip sets up, with latest ensemble means suggesting a little farther north (north Detroit suburbs up to I-69/M46 corridors). As the moisture overtakes the cold ground, fog may become widespread and dense at times today.

Temps are expected to make a surge well into the 50s, if not even low 60s this evening along the associated cold front. This may drive some weak surface based instability into Se Mi, especially south of the I-94 corridor. Given the strength of the low level wind fields, strong to perhaps isolated severe thunderstorms are not out of the question. Post frontal subsidence/isentropic descent along with strong cold air advection in the 06Z to 12Z Monday time frame will support an initial burst of gusty winds. Persistent cold air advection on Monday within the departing compact low will drive a longer duration period of strong winds. The subtle strength differences among the 00Z model suite will be the difference between how much the core of 50+ knot winds will be within the mixed layer, and suggests at this time either a high end wind advisory event or a high wind warning event with a few gusts over 60 MPH. Thus, the high wind watch remains the optimal headline at this time.

Deep wrap around moisture and enhancement off the lakes will support snow shower activity on Monday. Model soundings indicate steep lapse rates through 800mb, capped by a deep isothermal layer around -15 to -18C, suggestive of good dendrites. Available hi res guidance also indicates some enhanced boundary layer convergence along a secondary surface trough axis forecast to rotate across Se Mi during the first half of the day. These conditions along with the strong winds and sub freezing temps will increase the chances for snow squalls. Overall total snow accumulations Monday are likely to be highly variable with the gusty winds making precise measurements nearly impossible. Model/ensemble guidance suggests snow accums of a half inch to two inches across the area.

MARINE

Low pressure taking shape over the central Plains tracks into the Great Lakes this evening, rapidly deepening and producing a high magnitude wind field overnight through Monday. Ahead of the low, mild air spreads in today with rain becoming widespread. There is a slight chance for thunderstorms across the southern lakes this afternoon and evening. A powerful cold front then sweeps east across the region early Monday morning as the center of the low reaches peak intensity near northern Lake Huron. Widespread W to WSW gales ensue before a secondary arctic surge shifts wind direction to NW Monday afternoon. A 50 to 60 kt wind field wrapping around the system brings high confidence in gusts to gale force, and low confidence for gusts to 50 kt storms at times on Monday. The highest probability for these higher gusts appear to be over Saginaw Bay in the wake of the morning cold front, and later in the afternoon across southern Lake Huron where fetch is maximized. Ultimately, confidence in occurrence and duration remains too low for a Storm Warning at this time, but Gale Warnings are in effect for all marine zones into Tuesday. Snow squalls will increase in coverage and freezing spray becomes heavy Monday as the arctic air surges in. These will diminish slightly by Tuesday, but persist through much of the week within a continued arctic northwest flow pattern.

HYDROLOGY

Widespread rain with embedded heavier showers and thunderstorms will impact Southeast Michigan today into this evening. The more persistent region of heavier showers is forecast to be oriented along a west to east axis across the area. There is some degree of uncertainty with respect to the precise location of this region of more persistent rainfall, with recent trends suggesting along or north of the I-94 corridor to possibly as far north as the M 46 corridor. There is relatively high confidence for total rainfall amounts of an inch to inch and a half in this region, with roughly a 10% chance to exceed 2 inches. Localized minor flooding of urban and low lying areas will be possible.

PREV DISCUSSION

Issued at 1205 AM EST Sun Dec 28 2025

AVIATION...

Ceiling and visibility continue to drop across SE Mi as mild air moves into the region ahead of the large Midwest low pressure system. A surface warm front extends eastward from the low center across the Ohio valley and has a broad reach northward in terms of low stratus and fog. This allows an extended period LIFR to solidify along the SE Mi terminal corridor late tonight and then persist during the day as rain showers move in by sunrise. There is

DTW THRESHOLD PROBABILITIES...

* High for ceiling below 5000 feet tonight and Sunday.

* Moderate for visibility below 1/2 mi and/or ceiling below 200 ft Sunday, mainly in the afternoon.

* High for rain as precipitation type through Sunday.

* Low for thunderstorms late Sunday afternoon.

DTX WATCHES/WARNINGS/ADVISORIES

MI...High Wind Watch from late tonight through Monday evening for MIZ047>049-053>055-060>063-068>070-075-076-082-083.

Lake Huron...Gale Warning from 3 AM Monday to 11 AM EST Tuesday for LHZ361-362.

Heavy Freezing Spray Warning from 5 AM Monday to 11 AM EST Tuesday for LHZ361>363.

Heavy Freezing Spray Watch Tuesday morning for LHZ361>363.

Gale Warning from 1 AM Monday to 11 AM EST Tuesday for LHZ363-421- 422-441>443-462>464.

Small Craft Advisory until 4 PM EST this afternoon for LHZ441-442.

Lake St Clair...Gale Warning from 1 AM Monday to 7 AM EST Tuesday for LCZ460.

Michigan waters of Lake Erie...Gale Warning from 1 AM Monday to 7 AM EST Tuesday for LEZ444.