textproduct: Detroit/Pontiac

KEY MESSAGES

- Mild with high temps in the upper 30 to lower 40s today and mid 40s to around 50 degrees on Thursday.

- Widespread rainfall is expected on Thursday, along with gusty winds of 30-40 mph into Friday as well.

- There is the potential for any moisture on roadways to flash freeze Thursday night as arctic air moves back into the region.

- Scattered-numerous light snow showers Thursday night-Friday morning, with isolated embedded snow squalls possible into the afternoon. Snowfall accumulations up to an inch in the heaviest activity. Expect the Friday morning commute to be impacted and allow for extra time.

AVIATION

The passage of a weak cold front will bring a brief period of low- midlevel cold advection. Current data suggests the timing of the cold advection will not really pick up until after 12z. Did adjust and delay the timing for a couple of hours from north to south with regards to ceilings. Did take into account the current trends and did transition ceilings to low VFR to MVFR. There is uncertainty with how stout the low clouds will develop across the south given the lack of cloud to this point. There is also some uncertainty with the longevity of clouds after development as a very strong inversion will be in place. With daytime heating and some lowering of the inversion expecting VFR conditions for the afternoon. Nocturnal cooling this evening will likely result in non convective low level wind shear this evening. MVFR ceilings are expected to abruptly develop after 09z tonight.

For DTW...Uncertainty with timing of VFR low cloud this morning.

DTW THRESHOLD PROBABILITIES...

* Moderate in ceilings aob 5000 feet today. High after 10Z Thursday morning.

PREV DISCUSSION

Issued at 247 AM EST Wed Dec 17 2025

DISCUSSION...

Temperatures finally climbed above the freezing mark yesterday, yet Detroit's max of 34 degrees was still 3 degrees below normal. Temperatures have been below normal every single day this month. It will be even warmer today, with high potential to exceed 40 degrees if low clouds fail to materialize or are slower to develop this morning. Best chance of this occuring would be toward the southern Michigan border, as low level winds shifting to the west will allow for some moisture flux from Lake Michigan, which leads to higher confidence over the northern half of the CWA being locked into clouds with the frontal passage. On the flip side, locations toward the southern Michigan border look to be experiencing high based sprinkles over the next several hours.

Thursday will be the warmest day of the week with deep southerly flow ahead of our deepening storm system over the Midwest, as 165+ knot jet at 250 MB dives southeast from the northern Rockies. As a result, 500 MB trough axis even seen going negative tilted as it moves through the Great Lakes region/Ohio Valley Thursday evening/night. With 925 MB temps progged to be aoa 4 C during midday Thursday, the potential it certainly there for temperatures to reach 50 degrees, depending on the arrival time of rain showers. Because of this, southeastern areas of the CWA look to be the warmest. Pretty good agreement amongst the models with near a half inch of qpf, as the euro ensembles indicating just a 30-40 percent chance of exceeding half an inch across southern half of the CWA.

Frontal passage looks to be around midnight, with excellent low cold advection as 850 MB temps plummet to -16 C by 12z Friday. With 40+ knots of flow at 925 MB, occasional wind gusts of 30-40 MPH should be obtainable Thursday through Friday morning. Steep low level lapse rates with inversion height around 4 kft, which is rather shallow. However, what little cape that is generated does reside in the dgz. Thus, there is a low chance of snow squalls, as multiple westerly bands look to be coming off Lake Michigan. At the very least, scattered to numerous light snow showers are expected. with accumulations of up to an inch.

The fast tracking Pacific storms look to continue to track along the Canadian/United States border through the weekend into early next week. One cold front to roll through Saturday, with large area of high pressure tracking through Sunday-Monday morning, underneath some good upper level confluent flow. Warm advection/elevated warm front looks to be arriving late Monday, but best moisture/forcing looks to be over the Western Great Lakes region/northern Lower Michigan. The next cold front then progged for Tuesday already.

MARINE...

Cold front tied to the James Bay clips the region early this morning ushering in renewed northwest flow. The glancing shot of cold advection, with the core remaining north of Lake Huron, leads to a more marginal-type gale event for northern Lake Huron with a 3-5hr period where gusts will be capable of peaking in the 34-36kt range. Winds quickly weaken over the second of today as the northern edge of Ohio Valley high pressure drifts overhead. Another strong low then arrives over the northern Great Lakes Thursday leading to strengthening southerly flow by late tonight-early Thursday. Similar to Tuesday's system, warm advection limits overlake instability and subsequent mixing down of 50-60kt winds aloft. This however looks to only cap max gust potential at around 40kts with high probabilities to see frequent gusts to mid/upper 30kts due to a tighter gradient given the track over Lake Superior. There is signal for a brief lull in gales early Thursday night when the lead cold/occluded front crosses the region. A secondary arctic cold front is quick to follow however, crossing late Thursday night/early Friday, setting up strong W turning NW cold advection supporting gusts to gales for much of daytime Friday.

HYDROLOGY...

Milder temperatures bring snow melt across the area and widespread rainfall is expected Thursday from late morning into the evening. Maximum snow water equivalent in the deeper snow pack is currently around 1 inch. Basin average rainfall totals around half an inch are expected, which with the snow melt may lead to ponding on roadways. Rises on area rivers are likely late this week, but flood conditions are not anticipated.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until noon EST today for LHZ442-443.

Gale Warning until noon EST today for LHZ361-362.

Small Craft Advisory until 3 PM EST this afternoon for LHZ421-441.

Lake St Clair...Small Craft Advisory until noon EST today for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until noon EST today for LEZ444.