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KEY MESSAGES

- Lingering smoke-related air quality concerns into Monday.

- Strong area of low pressure drums up next chances for showers and thunderstorms at various times from late tonight through late Monday night.

- Aside from some lingering showers Tuesday, trending drier and cooler into midweek. Seasonably warm to close out the week.

DISCUSSION

Issued at 122 PM EDT Sun Jul 19 2026

Pattern / Forecast Synopsis:

NW flow regime still in full swing across the Great Lakes, with longwave troughing to our east over the Canadian maritimes, and a thermal ridge to our west running up the spine of the Rockies. Current surface analysis showcases surface high pressure basically right over our faces here in the Great Lakes, which has led to quieter and drier weather to settle in for today. A wider look at the surface map shows a deep area of surface low pressure moving into New Brunswick, Canada, with attendant cold frontal boundary (the one that swept through here the night before last) stretching down the Atlantic coast through roughly New York City before pivoting westward through the Cincinnati, St. Louis, and Kansas City areas. This front has largely stalled out, and will become a stationary front with time today, but remains of paramount importance to our forecast evolution.

Progressive flow will maintain the frequent passages of numerous weather features over the forecast period. As such, a potent shortwave trough is currently cresting the ridge in the Canadian Rockies, and its attendant surface cyclogenesis process is underway. This system will eject into the Canadian Prairies by tonight, riding the left exit region of a jet streak pointed straight at the Great Lakes region... with the left exit region oriented more or less overhead of the area Monday into Tuesday, and thus supporting surface pressure falls over the duration of the cyclone's journey through the Great Lakes. Result will be the drumming up of return flow into the region, and thus the northward re-advancement of the stationary boundary (now as a warm front) into the Great Lakes as the parent surface low zips through northern Ontario. Ample moisture and humidity will support a robust convective response somewhere across the Great Lakes region, with the warm front likely drawing the line between oppressive dewpoints well into the 70s south / west, and lesser (but still humid) dewpoints in the 60s north and east. This system will have a tight pressure gradient, which will drum up breezy NW winds Tuesday (and possible the return of more thick Canadian wildfire smoke, pending rainfall trends in NW Ontario) before surface high pressure builds back Wednesday, leading to drier weather through Thursday. By the weekend, the northwest flow regime aloft will supply additional subtle shortwaves into the Great Lakes region, which may drum up additional rain / storm chances.

Details:

Canadian Wildfire Smoke: Thickest smoke plume has been forced south and west by subtle NE flow through the night... currently residing over Wisconsin and leaking into the SW parts of the CWA. Anticipating the plume to largely pivot back through the region through the day, but with somewhat lesser smoke density than previous days (especially across northeast lower, where a lake breeze should flush out some of that smoke via easterly flow). As SW flow builds, anticipating this smoke plume to progress through the region some time between tonight and Monday afternoon (perhaps a window of lesser smoke later in the day Monday?)... with potential for more smoke on the backside of the Monday night - Tuesday morning system with NW flow, but that hinges on trends with rainfall and fire growth across NW Ontario and the Boundary Waters region of Minnesota. Regarding Air Quality Alerts from the Michigan Department of Environment, Great Lakes, and Energy (EGLE), the Air Quality Alert for elevated levels of PM2.5 particulate has been extended through Monday, stating levels unhealthy for sensitive groups will be realized across northern lower and eastern upper Michigan.

Rain / Storms Monday night - Early Tuesday: Starting off dry for most on Monday with increasing clouds as theta-e advection ahead of the incoming system materializes. Will have to watch the Whitefish Bay - Sault area for some elevated convection late tonight into Monday morning, but not anticipating any activity elsewhere. Through the day, warmer and more moist air is drawn into the region. Will see quite the gradient along the northward advancing warm front. Current trends support this boundary stalling out over the western Yoop, Wisconsin, and Illinois (limiting OUR surface dewpoints to the upper 50s - lower 60s, higher dewpoints in the 70s suppressed with the front), which would conceptually point the focus for vigorous convection to our south and west... but with mid level support from the approaching shortwave (and occluding surface cyclone), anticipating potential for storms to develop here nonetheless. Issue with this will be timing... with the arrival of the best synoptic lift failing to overlap instability here, could easily see decaying complexes of storms and stratiform rain traverse the region Monday evening through the overnight hours. This thought jives quite well with the latest SPC Day 2 Convective Outlook, which paints an Enhanced Risk (3/5) over western upper MI, WI, IA, and IL, while maintaining a Slight Risk (2/5) across much of the APX footprint, and a Marginal Risk near Lake Huron from Saginaw Bay to Alpena, which highlights the thought of decaying convective trends overhead quite well.

With increasing moisture content aloft, any storms that do form (along with any training convection setup that can materialize), activity should produce more efficient rainfall with time until the cold front passes through. As such, the likely scenario is barely sub-severe to lower-end severe storms (primary hazards in any severe storms: damaging winds, hail, and torrential rainfall... low but non- zero tornado chance) but on a relatively widespread scale. Certainly possible for some locales to see well over an inch of rain, but this appears to be rather localized at this juncture. Most spots probably realize a general 0.25-0.75" of rainfall. Of course, it is important to note that recent rainfall across the Tip of the Mitt south and east through APN is at heightened sensitivity for hydro concerns considering a general 2 to 4"+ of rain just fell the night before last. More details to come.

Breezy and Cooler Tuesday - Wednesday: The backside of the system will have quite the pinched pressure gradient, as such, cyclonic flow around the system will remain a bit breezy as cooler air spills into the Great Lakes. Current trends showcase potential for 15-20mph sustained NW winds Tuesday, with occasional gusts of 35mph+, especially along the lakeshores. With lingering trough axes passing through the region and slowly eroding surface moisture, suppose there is enough there to support shallow, low-level convective showers through the day Tuesday. Drier air does build by Wednesday, but with breezy conditions continuing... perhaps to the tune of 10- 15mph sustained NW winds and gusts as high as 25-30mph. Temperatures will suffer due to the increased cloud cover as well... likely struggling to top out much more than 65-75 most spots (coolest Wednesday), perhaps nosing into the low 80s near Saginaw Bay Tuesday.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 122 PM EDT Sun Jul 19 2026

Delicate mix of smoke and an elevated diurnal cumulus field across the region today, with some SKC mixed in downwind of Lake Michigan too. Anticipating conditions to hold VFR, barring smoke intrusions (currently 4SM at MBL). Persistent N to NW flow for the most part today, generally 15kts or less. May see a lake breeze intrusion at APN later this afternoon which may flip flow easterly there. Otherwise, winds trend calm with VFR generally prevailing. Will have to watch for fog / smog development late this evening, but any that does develop should be short lived, as S to SW flow picks up through the overnight, scouring any fog or smog out. Will have to watch for a shower or two in the vicinity of CIU, but overall, dry across the board. S to SW flow increases into the day on Monday, gusting perhaps as high as 25kts by afternoon, strongest in the vicinity of Lake Michigan and into CIU.

APX WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...None.