textproduct: Detroit/Pontiac

KEY MESSAGES

- Winter Weather Advisory is in effect for all of SE MI until 4 PM EST today. Ice accumulations between a tenth to just below a quarter- inch expected. Hazardous travel on untreated surfaces will be likely, in addition to isolated/scattered power outages.

- The potential exists for heavy rainfall Sunday as a strong winter system wraps up over the Great Lakes. Strong northwest winds appear likely late Sunday night and Monday behind an arctic front bringing snow showers.

- Below normal temperatures for the middle of next week.

AVIATION

A progressive upper short wave will drive a plume of warm moist air across Se Mi this morning atop a shallow layer of sub freezing air. This will result in widespread freezing rain. Regional radar suggests this will arrive at the terminals by 12Z. The peak period of ascent will be focused largely in the 13Z to 18Z time frame. The departure of the stronger forcing will coincide with temperatures rising above freezing, leading to a transition to rain and/or drizzle early to mid afternoon. The arrival of weak elevated instability in the 15Z to 18Z time frame indicates the potential for some embedded convective elements. Aggressive low level moisture advection this morning will result in steadily lowering ceiling heights, with IFR and LIFR conditions expected this afternoon. The development of a deepening low level inversion in the wake of the associated sfc low late this afternoon will likely drop ample low clouds in place into tonight; MVFR and/or IFR.

For DTW...The peak period of icing accumulation is expected between 12Z and 16Z before air temperatures rise above freezing. Isolated thunderstorms are possible across the airspace, mainly during the early afternoon.

DTW THRESHOLD PROBABILITIES...

* High for ceilings below 5000 feet today and tonight. * High for freezing rain this morning, high for all rain this afternoon.

* Low for thunderstorms today.

PREV DISCUSSION

Issued at 424 AM EST Fri Dec 26 2025

DISCUSSION...

The low pressure system now located over eastern Iowa remains on track to progress into southern Michigan through the morning and afternoon hours, which will produce widespread freezing rain, periodically mixed in with sleet at times across the northern Tri- Cities and northern Thumb. Surface temperatures now range between 27-32F with spc mesoanalysis highlighting h850 temperatures ranging between 1-6C, maintains freezing rain as the dominant p-type for this event. Precipitation to initially expand across SE MI through the mid- morning hours initially with the increasing surge of low- level moisture through h850 and more favorable moist isentropic ascent in the mid-level, expanding through h300 as the nose of the jet stream expands into the region. Initial precipitation will remain a little more scattered in nature as top-down saturation commences, Any initial freezing drizzle or rain observed prior to sunrise will be capable of produce a glaze of ice accumulation on untreated surfaces given the favorable dry surface conditions and nocturnal start time.

Rapid expansion of freezing rain footprint across SE MI will commence around to just after sunrise along a secondary and stronger surge of moisture, coincident with the arrival of low pressure over southwest lower. The bulk of the ice accretion will come with this secondary surge of moisture mainly between the hours of 12Z-17Z, with all precipitation tapering off from west to east between 17- 20Z. A couple of trends noted with the new overnight model data...QPF amounts continued to trend upward, with storm total qpf ranging between .40-.60". Hi-res output continues to highlight the potential for highly localized qpf totals to or in excess of 75" along the low-level circulation convergent axis from h875 to h775. Predictability remains low regarding where any of these mesoscale dominant features will setup as hi-res output highlights anywhere between I-94 up towards or just north of I-69 as a possibility. Additionally, mid-level lapse rates aoa 6C/km along with pockets of elevated instability bring chances for thunderstorm development with activity which brings more potential for localized higher qpf potential.

In terms of ice-to-liquid ratio/ice accretion potential, a few caveats to note -- Higher convective precipitation rates can lead to higher runoff potential, significantly lowering ILR. The advent of the aforementioned moisture surface also increases both the maxT and depth of the warm layer. Forecasted soundings show elevated MaxT values of 7-9C up through the M59 corridor during peak qpf potential, with warm noses ranging anywhere between 5000-7000ft. These warmer drops will have negative impacts on icing accumulation totals, but confidence is low regarding the exact degree this has on the final outcome. Despite elevated qpf potential, FRAM output (which does not factor in droplet temperatures) holds ice accumulation between .10" to just under .25". As noted in the prior evening update, strong consideration was given to a short fused ice storm warning for portions of SE MI, but at present time will retain a high-end winter weather advisory as confidence remains low for any widespread power outages or tree damage. Locations along and between M59 through I-69 and up into Saginaw/Tuscola county have the highest likelihood for ice accumulations that near or peak above two-tenths of an inch, especially through the Irish Hills where the nose of warm air aloft is not as prominent and surface temps are slightly cooler. Up through the northern Tri-Cities to northern Thumb, some sleet will be possible with cooler near surface conditions. Overall, expect hazardous travel on untreated surfaces along with isolated to scattered power outages.

Some transition to rain will be possible through the Metro region in the late morning to early afternoon as temperatures peak above freezing before all precipitation end from west to east 17-21Z. Low- level moisture holds up through 4kft in the evening and overnight hours, bringing some mist or patchy drizzle into the night. High pressure builds in Saturday morning, bringing dry conditions through the day, with the next low pressure system targeting Michigan Sunday morning through Monday morning. This dynamic system brings high likelihood for precipitation with main p-type as rain as 850 temperatures peak to or above 8C. Rainfall totals above a half-inch are looking increasingly likely with this system. A strong arctic front moves in in the wake of the low which would bring a transition to snow and would generate lake effect potential through the day on Monday along with windy conditions with possibly wind gusts to or in excess of 40 mph.

MARINE...

A compact low pressure system tracks across the southern Great Lakes today, producing a tightened pressure gradient and gusty east to southeast wind through the day. Sustained winds of 15 to 25 kt are expected with gusts to 30 kt over Lake Huron. Small Craft Advisories remain in effect through tonight for the nearshore waters from Outer Saginaw Bay to Port Huron due to onshore wave action over 4 feet. The system will also produce widespread wintry precip including snow, sleet, and freezing rain. A ridge of high pressure extending from southern Quebec will dominate conditions on Saturday with lighter east to southeast wind. A stronger low pressure system then tracks through the region Sunday night, bringing another round of widespread precipitation. A period of northwest gales, snow showers, and freezing spray is becoming increasingly likely Monday morning and afternoon as the system ushers cold arctic air back into the region.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Winter Weather Advisory until 4 PM EST this afternoon for MIZ047>049-053>055-060>063-068>070-075-076-082-083.

Lake Huron...Small Craft Advisory until 10 PM EST this evening for LHZ421- 441>443.

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