textproduct: Detroit/Pontiac

KEY MESSAGES

- Widespread light snow expected Sunday morning into early afternoon. Snow accumulations to range between a half-inch to two inches for most locations.

- Below normal temperatures continue this week, the coldest of which arrive Monday and Tuesday. Wind chill temperatures drop to or below zero Monday morning.

- Active weather pattern continues into the midweek period where additional snow chances will be possible.

AVIATION

Low level cold advection in the wake of a weak cold front will facilitate low VFR to MVFR stratus tonight. A wave of low pressure will then track out of Iowa through portions of northern Indiana and Ohio Sunday morning. Plan view of RH progs support low level dry air holding on across Southeast Michigan including the Detroit terminals that will require moistening. A combination of isentropic ascent and absolute moisture advection will bring a chance of light snow to Southeast Michigan mainly after sunrise Sunday morning. The active sequence of system relative isentropic ascent with this system appears to be very brief mainly only lasting in the 10-14Z time window. Any additional precipitation will then work off of some absolute moisture overrunning into the state that should become more increasingly undercut with time. The inherited time period of IFR light snow remains good. Around an inch of snow is possible for the southern taf sites. Lesser amounts and KFNT and KMBS. VFR skies Sunday afternoon with northwest wind of 10 to 20 knots.

For DTW...IFR Light snow will push into Southeast Michigan Sunday morning. The most likely time period is between 10 and 16z. Snowfall amounts of around 1 inch possible. VFR conditions Sunday afternoon.

DTW THRESHOLD PROBABILITIES...

* High for ceiling at or below 5000 ft tonight and Sunday.

* High as precip type being all snow Sunday morning.

PREV DISCUSSION

Issued at 244 PM EST Sat Dec 6 2025

DISCUSSION...

Weak cold frontal boundary finally pushed east of the region early this afternoon however lake moisture trapped below the post-frontal inversion has maintained cloudy skies across lower MI. Despite ongoing weak cold advection through the evening, this cloud cover keeps lows a few degrees warmer than they'd otherwise be instead holding in the lower 20s to upper teens.

Next chances for snow quickly arrive Sunday morning as a weak shortwave ejecting from the central Rockies reaches the southern Great Lakes/Ohio Valley. Despite the wave track south of the state line, areas north of M-59 actually look to start earliest, around 09- 10Z, tied to developing interaction with a northern stream mid-level trough diving across the northern Great Lakes. Isentropic ascent fills in across the remainder of SE MI over the morning with all areas likely seeing light accumulating snow by 12Z. Strongest isentropic ascent and subsequent peak snow rates trails lead precipitation by a couple hours arriving closer to mid-morning as the parent vorticity reaches northern IL/IN. High res models have begun backing away from earlier hints at potential f-gen banding keeping rates on the lighter side between 0.1-0.25"/hr (highest in the south where wave positioning offer greater moisture/forcing). A potential exception to this northern Thumb where continues to be a subset of high-res guidance suggesting a convergence axis off the Saginaw Bay/central Lake Huron enhancing rates. Ohio Valley surface circulation rapidly weakens over the late morning-afternoon period as the aforementioned northern stream trough takes over spurring new surface low development over the eastern Great Lakes. Locally, this tapers off snowfall by late afternoon. Total accumulations still look to be on track for 0.5-2" across the CWA though should the lake convergence axis manifest, areas from Sebewaing to Grind Stone City could approach 3".

Arctic high pressure follows for Monday bringing a brief reprieve in the active pattern. The promotion of clearing skies Sunday night as the high builds in sets the stage for another very cold night with morning lows in the single digits and wind chills nearing 0 for the majority of the region. With the ridge axis not crossing the state until Monday night, thermal recovery is minimal as daytime highs Monday hold in the mid 20s and Monday night lows fall near 10.

A baroclinic zone is set to linger over lower MI through next week following the departure of high pressure late Monday allowing a series of clippers to track near or over the region almost everyday into next weekend. First of these arrives daytime Tuesday as a wave passing near the Straits offers light snow accumulations, mainly over the northern half of the CWA. A stronger, more dynamic shortwave is then progged to sweep out of the northern Plains and directly over southern MI Wednesday. This current track allows a degree of milder air to be partially advected into lower MI which would support mixed precip (rain-snow) for at least a portion of the area.

MARINE...

Northwest winds gusting 25-30 knots over Lake Huron this afternoon will diminish this evening and tonight as a ridge of high pressure builds over the Central Great Lakes, dropping winds under 15 knots everywhere. Weakening low pressure tracking through the Ohio Valley tomorrow will bring widespread light snow Sunday morning, trending toward more localized snow squalls over Lake Huron late Sunday as 850 MB temps lower into the negative mid teens. Northwest winds gusting between 25-30 knots appear likely late in the day. However, winds then look to veer to the north-northeast fairly quickly and weaken Sunday night as high pressure quickly builds in for Monday morning. None-the-less, large waves of 6+ feet will build over the southern Lake Huron. Some of these larger waves look to clip the nearshore waters of Lake Huron as winds veer around, and have issued another round of small craft advisories for late Sunday afternoon into into Monday morning for Outer Saginaw Bay and the nearshore waters of Lake Huron from Port Austin to Port Huron.

Brief southwest gales possible on Tuesday as low pressure tracks through the northern Great Lakes. A larger and stronger low pressure system is then on track to move through Lower Michigan Tuesday night into Wednesday producing widespread snow and even changing precipitation to rain over Lake St. Clair and Lake Erie. Rush of cold air behind the passage of the low will support strong northwest winds late Wednesday and Wednesday evening. Isolated, brief gusts to gales will be possible, but the pressure gradient quickly relaxes by Thursday morning.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory from 3 PM Sunday to 10 AM EST Monday for LHZ421-441>443.

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