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KEY MESSAGES

- High impact winter storm to continue through Monday. Very heavy snow, significant ice accumulations, and increasingly gusty winds will impact much of the area.

- Gradually moderating temperatures and chances for mostly light precipitation at times heading through the remainder of the week.

DISCUSSION

Issued at 211 PM EDT Sun Mar 15 2026

Pattern Synopsis/Forecast:

Well advertised major late season winter storm unfolding about as expected early this afternoon, with steadily deepening surface low (circa 990mb's) across western Illinois. All parameters remain on the table for this low to hasten its deepen process as it heads into lower Michigan this evening, with strong upper level diffluence via nice coupled jet structure, digging and deepening upstream deep layer troughing, and an increasingly robust multi-layer thermal gradient layed out across Michigan. Strong isentropic upglide/deep moisture convergence on nose of low level jet helped drive a band of moderate to heavy snow from south to north across our area this morning, with focused low elevated convergence now centering this band across the Tip of the Mitt into eastern upper Michigan. Intense snowfall rates continue, helped by excellent frontogenetical response within zone of maximum deep layer moisture convergence. Mid level dry wedge has spread across a good portion of northern lower Michigan behind this band, with next round of moderate to heavy precipitation tied to that axes of upper level divergence and focused low/mid level convergence now beginning to move into western sections of northern lower Michigan. Northward shooting elevated warm layer has resulted in this precipitation become much more "mixy," with sleet and freezing rain along its southern periphery.

As mentioned, surface low pressure will deepening fairly rapidly this evening and overnight (dropping to near 980 mb's) as it swings up across lower Michigan...reaching vicinity northern Lake Huron by later Monday morning. Parent mid level troughing will deepen quickly as well, with closed mid level low sweeping across the northern Lakes Monday afternoon and early evening. Upper level flow regime relaxes substantially heading into the remainder of the week, with broad troughing dominating much of the eastern Conus.

Primary Forecast Concerns:

All attention directed at precipitation type concerns, amounts, and attendant headline considerations tonight into Monday.

Details:

Still a very challenging forecast heading into tonight and Monday morning as precipitation type and amounts will be highly sensitive to a very complex and robust low level thermal gradient regime across northern lower Michigan. With that said, latest observational trends fully supporting the surface based cooling across parts of northwest and north central Michigan observed in latest guidance output. However, northward protruding warm nose has not been lost...again setting up a messy and likely significant mix of precipitation across northern lower Michigan.

Handling the easiest portion of this forecast first: still appears the vast majority of this event will fall as snow across most of eastern upper Michigan. And...that snow will be significant and prolonged to say the least, with initial warm air advection wing of forcing replaced by increasing deformation and trowal driven dynamics later tonight through Monday. Full range of probabilistic guidance continues to show exceedingly high chances for storm total snow amounts of 18 to 24 inches...with some areas perhaps making a run at 30. Combine those insane amounts with gusty winds...at times up and over 40 mph...and current blizzard warnings are more than justified. Some sleet will likely mix in at times across far southeast and southern portions of eastern upper Michigan, cutting back a bit on overall accumulations there. High impact none-the-less.

Again, trouble area remains across parts of northern lower Michigan given the northwest arching with height thermal gradient. Cooler surface trends noted in observations and convective allowing guidance remain disconcerting with regards to freezing rain potential across parts of northwest and north central lower Michigan. Trends support a swath of quarter to half inch ice amounts (locally higher) from southwest of Grand Traverse Bay northeast to Roger City by sunrise Monday. More a wintry mix of snow, sleet and freezing rain to the northwest of this line, with primarily rain further southeast as surface rooted above freezing layer slowly expands north with time. Again, exact axis of heaviest freezing rain will likely change as final alignment of both elevated warm layer and northward extent of above freezing temperatures materializes. Unfortunately, whoever gets into the heavier freezing rain will likely see significant impacts...to include power outages and tree damage...with both of these being exacerbated by increasingly gusty winds during the day Monday. And, unlike last years historic ice storm, the ground temperatures are several degrees colder with this event...supporting very icy driving conditions as well.

Decaying deformation and trowal will sweep steadily southeast across the area Monday into Monday evening. While widespread snow and mixed precipitation will decrease in organization and intensity later on Monday into Monday evening, a growing lake contribution in favored northwest flow areas will produce some locally heavier snow showers. Probably of greatest concern will be the gusty winds...easily up and over 30 mph at times...with gusts in excess of 40 mph near the Great Lakes. This will not only promote some blowing and drifting snow, but as mentioned earlier, could also have significant impacts if those heavier freezing rain amounts are indeed realized.

Only a glancing look at the rest of the forecast. Gradual moderation is expected, with highs much closer to normal by Thursday and Friday. Additional chances for some light precipitation at times, but definitely not seeing any significant systems.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 125 PM EDT Sun Mar 15 2026

Main area of heavier snow continues to push northward into the eastern UP, although KPLN will likely continue with moderate to heavy snow for several hours. Next batch of a wintry mix of snow sleet and freezing rain will work into the region through the rest of this afternoon and into the evening and overnight, with significant icing possible at KTVC, and to a lesser extent KAPN. CIGs remain in the MVFR to IFR range mainly with VSYBs ranging wildly with 1/4 SM in heavy snow, and between 1 to 3SM within the more wintry mix. Main heavier precip moves out Monday morning, replaced by lake effect snow and continued gusty winds.

APX WATCHES/WARNINGS/ADVISORIES

MI...Winter Storm Warning until 8 PM EDT Monday for MIZ016. Ice Storm Warning until 8 AM EDT Monday for MIZ017-018-020>023- 026>028-099. Winter Weather Advisory until 8 AM EDT Monday for MIZ024-025- 029-031>033. Blizzard Warning until 8 AM EDT Tuesday for MIZ086-087-095-096. Winter Storm Warning until 8 AM EDT Tuesday for MIZ088-097-098. MARINE...Gale Warning until 8 AM EDT Tuesday for LHZ345>349. Gale Warning until 8 AM EDT Tuesday for LMZ323-341-342-344>346. Gale Warning from 8 PM this evening to 8 AM EDT Tuesday for LSZ321-322.