textproduct: Marquette

KEY MESSAGES

- Patchy frost is possible for areas of the interior UP where temperatures fall into the mid 30s early tomorrow morning.

- Scattered showers and a few thunderstorms move west to east Thursday afternoon through early Friday morning. Rainfall amounts will be light, generally around 0.1" or less.

DISCUSSION

Issued at 226 PM EDT Wed Aug 19 2026

Early afternoon GOES satellite imagery reveals blossoming diurnal cu across the UP underneath increasing surface high pressure on the southwestern flank of a departing upper level low. A limited fire weather risk may be shaping up as local observations have RHs falling between 35-50% and wind gusting between 10-20 kts. With continued mixing into a very dry low-level airmass, RHs may continue to fall into the low 30s to upper 20s, moreso across the interior west and central UP. As winds decrease this evening and RHs recover, fire weather concerns depart. Another forecast challenge presents itself tonight regarding low temps. Under clearing skies, save for maybe some high cloud advection in the western UP, radiational cooling may allow portions of the interior to fall into the upper 30s. Not planning any Frost Advisory headlines as confidence is low regarding widespread 32-35 degrees, but if you're concerned about protecting your plants may err on the side of caution tonight.

The next shot at precipitation returns tomorrow evening into the overnight hours through early Friday as a low amplitude shortwave within northwest flow aloft traverses the area. Showers reach the western UP tomorrow afternoon and continue into the central UP by the evening, however, given the stout dry airmass in place, thinking the eastward migration of rain may be slowed some. Initially cannot rule out a rumble of thunder in the west half, but unfavorable timing for diurnal instability and weak kinematics gives low confidence on much more than a rumble. By Friday morning, CAM ensembles only point towards a 50-80% chance for amounts greater than a dime, so do not be expecting meaningful rainfall for your gardens. Isolated amounts between a dime and quarter are more likely in the western half where better saturation occurs. Another round of showers/storms along a cold front, mainly in the central UP.

Mostly dry through the rest of weekend with a chance of showers/marginal thunderstorms Saturday afternoon, though the main story will be marine hazards and gusty northerly winds Saturday/Sunday as a pair of sharp shortwaves dive south-southeast from the Hudson Bay down into the Lower Great Lakes. Modest pressure rises coupled with cold air advection (850 mb temps between 3-6C Sunday) will create northerly gusts 20-30 kts with a 40% chance of gales to 35 kts.

Model discrepancies follow into next week, though the first half looks mostly dry at this time.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

Issued at 135 AM EDT Thu Aug 20 2026

VFR conditions this morning give way to rain showers and potentially a few thunderstorms over at least the western two terminals this afternoon into this evening. As the shortwave low responsible for the rainfall comes in today, some MVFR or lower conditions could be seen over IWD and CMX this afternoon and evening via moderate to heavy rainfall and/or lowered cigs (~20 to 30% chance each hour for several hours). Rainfall chances don't appear to approach SAW until nearly midnight tonight.

While winds pick up from the south today, there is high uncertainty on the wind direction for SAW this afternoon; should the Lake MI lake breeze not win-out, expect to see more northeasterly winds than southerly winds in the afternoon via the Lake Superior lake breeze before flipping to the south by the overnight hours. However, should the Lake MI lake breeze win-out, expect to see the southerly winds continue over SAW this afternoon through this evening.

Finally, while there is a low chance for some marginal LLWS to be seen over the western two terminals for maybe an hour or two tonight, given the low chances and marginal nature, decided to not include mentions of it in the TAFs at this time.

MARINE

Issued at 226 PM EDT Wed Aug 19 2026

Lake Superior - Light winds 15 kts or below remain through Thursday morning. Southerly winds increase 15-20 kts in the eastern lake Thursday evening before falling back below 15 kts Friday. The main marine hazards return Saturday and Sunday as a pair of systems bring modest pressure rises and cold air advection over the Lake resulting in gusty N to NW winds upwards of 20-30 kts beginning Saturday morning through Sunday night. At this time, there is a low chance (20-40%) for a few gales to 35 kts mainly between Marquette and Whitefish Point.

Northern Bay of Green Bay and northern Lake Michigan - Breezy southerlies upwards of 15-20 kts increase tomorrow morning and linger through Friday as low pressure traverses the area. This results in waves building between 1-3 ft (greatest in the open waters closer to Lake Michigan). A brief reprieve in winds comes Friday night behind a weak cold front, however, two systems then dive into the area Saturday and Sunday, resulting in gusty north to northwest winds 15- 25 kts through at least early Monday.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... None. Lake Superior... None. Lake Michigan... None.