textproduct: Detroit/Pontiac

KEY MESSAGES

- Winter Weather Advisory in effect Friday for all of Southeast Michigan. Widespread freezing rain and impacts to travel are anticipated. Ice accumulations between a tenth and two tenths favored with locally higher amounts possible. Around an inch of snow and sleet mix possible in the northernmost portions of the Thumb.

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

- Below normal temperatures for the middle of next week.

AVIATION

Dry and colder air in the low levels off northern Ontario high pressure has effectively displaced MVFR clouds from SE Mi this evening. Earlier NE wind in the 10 to 20 kt range did most of the work and remains steady around 10 knots tonight to further reinforce cold and dry air across the region. This sets the stage for freezing rain arrival shortly after sunrise with similar onset timing along the terminal corridor. A rapid drop from VFR into low end MVFR ceiling and visibility occur as precipitation intensity increases during the morning. A mix of freezing rain and sleet is more likely toward MBS, greater intensity freezing rain from FNT to PTK, and a lighter intensity toward DTW. All areas see icing of at least 0.1" with higher totals to around 0.2" beginning to show focus from PTK to FNT until the pattern exits around mid Friday afternoon.

For DTW... Confidence remains high in freezing rain Friday morning to early afternoon. Freezing rain is expected to begin around 12-13z and continue through 18z before tapering off through the mid- afternoon. Ice accumulations between 0.1" to 0.2" are possible, but with potential for temperatures to climb slightly above 32 degrees by late morning which could reduce these amounts.

DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 feet or less Friday. * High for freezing rain Friday morning through mid-afternoon.

PREV DISCUSSION

Issued at 403 PM EST Thu Dec 25 2025

DISCUSSION...

Surface ridge axis extending south of the James Bay region will work across Southeast Michigan this afternoon and tonight. Northeast surface trajectories areawide and dewpoints ranging in the 20s point to the influence of the anticyclone and ridge axis. Both sun and clouds across the forecast area earlier today with a blanket of stratocumulus downwind of Lake Huron and increasing high cloud in advance of Fridays system. Very quiet weather for outdoor interests the remainder of this afternoon and evening; temperatures dropping into the 20s.

The biggest model trend/tendency of the 25.12Z model suite was toward solution convergence regarding QPF. In fact, saw many hires CAMs arrive wetter with QPF amounts and with a shift of the QPF swaths northeast, much more in line with the consensus of the Global Determnistics of the past few days. High confidence exists in a widespread freezing rain event for Southeast Michigan Friday beginning after 10z and persisting until mid Friday afternoon. The potential does exist for sleet to mix in with the freezing rain and cut back on the icing amounts. Widespread impacts to the morning commute and holiday travel are anticipated and the decision was made to issue a Winter Weather Advisory hazardous road conditions.

A high amount of uncertainty remains with this Friday system, particularly with the overall potential for higher end QPF and its exact placement/positioning (i.e. potential impacts). A rather robust consensus exists out of the 25.12z Deterministics for a swath of 0.50 to 1.00 inch QPF varying in north to south extent from I 94 corridor to the I 69 corridor. More comprehensive datasets do not necessarily agree with the AIGFS/EC-AIFS offering QPF of 0.30-0.40 inch, 75th percentile of the EPS ranging .40 to .60 inch. Want to communicate that heavy precipitation rates will be possible owing to the strength of the 925-850mb low pressure circulation that forces the wave of substantial warm advection. The first wave of 600mb thetae advection after 10z opens the door for precipitation to reach the ground, but it is the secondary midlevel moisture surge between 15-18Z that will be a key player. Plan view of moisture and isentropic surfaces suggests a thetae gradient lifting northward and potentially stalling into the higher elevation areas of northern Metro Detroit eastward to eastern St Clair County. Plenty of discussion here regarding what the efficiently of accretion will be if the higher/convective precipitation rates occur. Uncertain that water from heavier and shorter duration rates will be able to freeze highly efficiently, instead running off objects given a modest southeast wind. In addition, will be looking at a modified air mass of sorts with wind trajectories off the lake aggregate of Lake Erie and Lake St. Clair with many datasets climbing towards 30-32F mark. The one exception could be portions of St Clair county between Port Huron and Harsens Island westward through northern Macomb to northern Oakland counties where wind trajectories could work around the southern end of Lake Huron and hold a better wet bulbing potential. If this type of environment were to align with a stalling of the thermal gradient and the horizontal/uvv circulations collapse in scale then could see a scenario where power outages would be a much bigger issue. Will need to continue monitoring model/data trends heading into the event tomorrow for any potential headline changes.

High amplitude, record breaking upper level ridge pushes across Southeast Michigan on Saturday and Sunday. Anomalously strong inversion is anticipated with 850mb temperatures of +9-10C at 850mb. The next dynamic system is set for Sunday with a very sharp cold front. A few main points with the Sunday system. Magnitude of warmth and PWATS will support heavy rainfall potential with some data suggesting amounts of an inch or more in vicinity of Southeast MIchigan. Projected absolute vorticity advection and projected thermal gradient along the cold front suggests thunderstorms could be possible Sunday evening. Lastly, the potential still appears likely for strong synoptic wind potential late Sunday and Monday. Much colder air to follow Tuesday and Wednesday.

MARINE...

High pressure passing to the north of the Great Lakes veers wind direction from northeast this afternoon, to east this evening, to east-southeast Friday morning. Magnitude will be 15 to 20 kt tonight before increasing to 20 to 25 kt on Friday as a compact low pressure system tracks across the southern Lakes. Gusts increase to around 30 kt on Lake Huron before weakening Friday evening as the system departs. The onshore flow will maintain a heightened wave field across southern Lake Huron and a Small Craft Advisory remains in effect for the nearshore waters from Outer Saginaw Bay to Port Huron through Friday night. 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 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 and gusty northwest wind on Monday as colder air moves back in. A period of gales is becoming increasingly likely Monday morning and afternoon.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Winter Weather Advisory from 5 AM to 4 PM EST Friday for MIZ047>049- 053>055-060>063-068>070-075-076-082-083.

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

Lake St Clair...None.

Michigan waters of Lake Erie...None.