textproduct: Marquette

KEY MESSAGES

- Widespread 1 to 4 inches of snow moves through the UP tonight through Saturday morning. The highest amounts are expected in the east half, lowest closer to the WI stateline.

- Lake effect snow for the west to northwest wind snowbelts increases tomorrow afternoon through Sunday morning.

- A Wind Advisory is in effect for Keweenaw and Northern Houghton counties Saturday afternoon through Sunday morning for westerly wind gusts upwards of 45 mph.

DISCUSSION

Issued at 318 PM EST Fri Dec 19 2025

Early afternoon satellite imagery reveals N to NW lake effect snow showers streaming across Lake Superior as the system responsible for this morning's snowfall and high winds has now reached Quebec. The encroaching midlevel ridge and drier airmass from the Upper Midwest will work to eat away lake induced equilibrium down below 5k ft and taper off lake effect snow showers from west to east through the evening. Despite the quieting lake effect activity, the next round of somewhat impactful winter weather arrives tonight as a descending trough out of the Canadian Prairie skirts a ~995 mb surface low pressure just north of Lake Superior through Saturday. Isentropic ascent on the southern flank of the clipper low will be the primary forcing mechanism for light to moderate snowfall beginning across the west-central UP around midnight, continuing east through daybreak. Model soundings depict a stout midlevel dry layer, so precip start may be delayed a few hours if dry air wins out. By the morning commute hours, widespread light snowfall should be occuring across much of the UP. In the east, south-southwest flow off of Lake Michigan may provide a local enhancement to snowfall production. This is supported by the most recent 12z HREF, which suggests a 50- 75% chance for snowfall rates >0.5"/hr during the 7-10 AM timeframe. The quick moving clipper departs east by early afternoon, leaving behind a light 1 to 4 inches of snow, with the highest amounts in the east half and lowest along the UP/WI border. Behind the departing low, chilly W to NW flow characterized by 850 temps sub -20C will begin to uptick lake effect snow for the traditional W to NW wind snowbelts. There, another fluffy couple of inches is possible in the Keweenaw and along/north of M-28 Saturday afternoon through Sunday morning. Coupled with the snow, the system's tight pressure gradient will be responsible for increasing southerly winds tonight, commonly reaching speeds of 25 to 35 mph. Once the winds veer to the W and NW, mixing into a 40-50 kt LLJ will help bring down gusts of 40-50 mph in the Keweenaw. Thus opting to issue a Wind Advisory for Keweenaw and N Houghton counties Saturday afternoon through early Sunday morning. Gusty winds in combination with falling snow may locally reduce visibility below 1 mile or less!

Looking into the coming workweek, lake effect snow will taper off into Monday ahead of a weak that may provide some light snow to the area. Otherwise, a warming trend is afoot as building heights across the central CONUS allow daytime temps to push into the 30s and even low 40s by Christmas. No particularly impactful storms seem to take aim at the Upper Great Lakes during this timeframe as well.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 1242 AM EST Sat Dec 20 2025

Brief improvement to VFR is currently prevailing at IWD and CMX ahead of the next system. But, MVFR lake clouds and lake effect snow showers have been persistent at SAW all night. And, all TAF sites are going to deteriorate again to MVFR/IFR in the Sat 06-09Z time frame as the aforementioned system brings another round of snow. In addition, LLWS will be a threat early this morning for 45 kt winds below 2k feet at both IWD and SAW. At the surface, strong southerly winds will gust to 30 to 35 kts today. Gradual improvement to MVFR can be expected late this morning, but any prevailing VFR is unlikely through the end of this TAF period.

MARINE

Issued at 318 PM EST Fri Dec 19 2025

Impactful marine weather remains in the forecast as a surface low pressure moves just north of Lake Superior tonight through Saturday afternoon. Southerly winds begin to increase tonight through early Saturday, increasing to gales of 35 kts across the east and north- central lake. As the system kicks to the northeast of the lake through tomorrow morning, southerly winds will veer to the west and northwest. There, strong pressure rises coupled with mixing into the 40-50 kt low level jet will ramp up wind gusts upwards of 45 kts across the western lake, spreading to the central and east by the afternoon. Significant wave heights of 15-20 ft are possible west of the Keweenaw by tomorrow early afternoon, then east of the Keweenaw for much of the open waters overnight into Sunday morning. At this time, there is a 25% chance for storm force gusts to 50 kts. Gale Watches have been upgraded to Gale Warnings for nearly all of Lake Superior. In addition, heavy freezing spray is likely tomorrow afternoon into Sunday morning as temperatures fall into the teens and 20s lakewide. Winds begin to decrease below Gale from west to east Sunday morning.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Wind Advisory from 1 PM this afternoon to 1 AM EST Sunday for MIZ001-003.

Lake Superior... Gale Warning from 7 AM EST /6 AM CST/ this morning to 1 AM EST /midnight CST/ Sunday for LSZ162-240>243-263.

Heavy Freezing Spray Warning from 1 PM EST /noon CST/ this afternoon to 7 AM EST /6 AM CST/ Sunday for LSZ162- 240>244-263-264.

Gale Warning from 7 AM this morning to 7 AM EST Sunday for LSZ244-264.

Gale Warning from 11 AM this morning to 7 AM EST Sunday for LSZ245>248-265.

Heavy Freezing Spray Warning from 4 PM this afternoon to 8 AM EST Sunday for LSZ245>251-265>267.

Gale Warning from 4 PM this afternoon to 7 AM EST Sunday for LSZ249>251.

Gale Warning until 7 AM EST Sunday for LSZ266.

Gale Warning from 4 AM early this morning to 7 AM EST Sunday for LSZ267.

Lake Michigan... Gale Warning from 4 PM this afternoon to 1 AM EST Sunday for LMZ221-248-250.