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KEY MESSAGES

- Times of showers and storms today with the primary threats of heavy rain and hail

- Widespread mixed precipitation chances return late Wednesday and will linger into early Thursday. Still uncertainty with what happens during the day Thursday.

- Unsettled pattern continues through the weekend, brining below normal temperatures which will linger into the early part of next week

DISCUSSION

Issued at 136 AM EDT Tue Mar 31 2026

Current surface observations depict a warm front stretching from west to east across central northern lower this morning. Satellite shows a stream of Pacific moisture being carried along an upper jet over the northern CONUS meeting with a low level plume of gulf moisture near the Great Lakes region this morning. This plume of lower level moisture transport towards northern MI has been aided by a LLJ over the southern part of the state as well as over IL/IN. The influx of moisture, strong winds and wind shear, and warmer temperatures within the LLJ all explain why there is blossoming convection over northern lower this morning. Modeled soundings depict around 700 to 1000+ j/kg of elevated instability, as well as mid level lapse rates of 7C/km. Winds shear of 30+ kts is also seen from the sfc up to 1km and increases up the column. This higher shear environment is also apparent while looking at radar, fast moving storms with tilted updrafts. Heavy rain and lightning are being seen by most storms, with a few of the stronger storms producing hail greater than half of an inch in diameter. The lower level inversion is keeping damaging wind threats at bay, however an isolated stronger gust cannot be ruled out especially south of M-55 which is closer to the warm front boundary.

As an area of surface low pressure will reach over northern MI near sunrise this morning, it will bring drier air from the central plains with it. Cloud cover will begin to fill in, with chances for isolated embedded storms lingering. PWATs will decrease from just over an inch down to 0.8", keeping a couple hundred j/kg of elevated instability around. Mid level lapse rates remain around 7 C/km, and ample wind shear still exists around this time as well.

As the surface low exits to the east (over Lk Huron), a cold front will start to move through around midday today. The second wave of scattered to numerous showers and storms will be seen ahead and along of the boundary beginning mid to late morning, as moisture amounts rebound (PWATs back to 1"). The main threats with storms will be heavy rain and lightning, with a handful of stronger storms being capable of producing hail around a half inch or greater and gusty outflow winds. Behind the front, colder air will settle in for tonight. The surface high will be anchored over the far southern part of the Hudson Bay, providing cool east to northeast winds over northern MI Wednesday.

Over the intermountain west, a pattern change is occurring. An upper level trough is forecasted to move over the central and southern Rockies. This will bring Pacific moisture to the central plains, and also deepen an existing lee side low near NM/OK. Late Wednesday into early Thursday, that trough will eject over the central plains. A strong southwesterly LLJ will be seen during this time over the central plains and up to the Great Lakes states. This will advect warmer air up and over the anchored surface high early Thursday. This will be a favorable system to produce heavy precipitation somewhere in the northern plains and/or Great Lakes region Thursday (robust jet dynamics, ideal isentropic ascent, and moisture availability). Global ensembles still keep a healthy amount of disagreement in the evolution of the upper trough, and thus the track of the surface low. The majority of global ensembles favor tracking the center of the low over either northern MI or across the U.P. and into Lk Superior. The first track would yield a more prolonged window of mixed precipitation for much of northern MI (snow is eastern upper), with the second track generating mixed precip initially but transitioning to mostly rain with some thunder chances. Guidance is leaning strongly on advecting the 0C 850 mb line to at least the bridge, which makes sense with the strong southwesterly jet over the central plains. This adds confidence to either of these scenarios, vs a more south track that would produce mostly snow over all of northern MI.

Ensembles and global guidance is leaning towards favoring the warmer solutions, with keeping the 75th percentile (reasonable worst case) capped at 0.2" of ice accumulation for Thursday across eastern upper and the higher hills of northern lower. With that said, a few outliers still do generate impactful ice across parts of northern lower and/or eastern upper (impactful ice being >0.2"). Although impactful accumulating snow is less likely, some outliers are producing up to +5" of snow over eastern upper and near the Lk Huron shores of northeast lower. To summarize, guidance is favoring widespread mixed precipitation late Wednesday into early Thursday; with two main solutions diverging and one keeping mixed precip during the day with another brining warm rain to much of northern lower during the day Thursday. Further details will resolved as we get closer.

The pattern remains active as a larger upper low will move across the western CONUS towards the central and northern plains. Chances for rain and possibly times of light snow will linger through the weekend.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1256 PM EDT Tue Mar 31 2026

Showers and embedded thunderstorms will work across much of northern MI this afternoon into early evening with CIGs largely varying from IFR to MVFR. Best chances for any embedded storms will be across northern lower Michigan where a strong storm or two cannot be ruled out. Flight conditions are expected to improve back to MVFR area-wide later this evening/tonight with increasing probabilities for VFR during the day Wednesday.

APX WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...Small Craft Advisory until 8 PM EDT this evening for LHZ348.