Merrill, WI Weather

Key Messages

- Areas of fog, locally dense, possible again late tonight into Friday morning.

- Mild into the weekend, with high temperatures inland of Lake Michigan warming into the mid 60s to low 70s.

- Light rain chances (20 to 40%) return Saturday evening, continuing at times through Monday. Rain chances linger through much of next week.

- Cooler next week, with highs mainly in the 50s.

Discussion

Issued at 1215 PM CDT Thu Oct 22 2026

Fog... Onshore breeze off the Bay has kept patchy fog around portions of east-central into far northeast Wisconsin through early this afternoon, though dense fog has lifted. Signal then once again exists for fog development late tonight into Friday morning due to continued onshore flow and light winds aloft, though remain uncertain if this will materialize as fog or low stratus. CAMs remain divided in this regard, though current thinking is that there may be just enough mixing to keep low stratus deck elevated. Radiational cooling late tonight is also not looking as good as it did this morning. For the above reasons, have opted out of issuing an advisory, though trends will have to be monitored into this evening.

Rain chances... Light rain chances increase Saturday evening as low pressure ejects into northern Canada and trailing cold front progresses over the upper Midwest. Moisture return along the slow- moving boundary will nudge PWATs into the 1 to 1.25" range Saturday into Sunday (~90th percentile), which should work in tandem with upper jet energy to keep periodic rain chances in the forecast through the weekend. Blended PoPs continue to trend in the 20 to 40% range, though suspect these will have to be increased within the next day or two with front in the vicinity. NBM probabilities show a 20 to 40% chance for receiving 0.25" of QPF through Monday. Beyond Monday, similar pattern of on/off rain chances exists as upper flow flattens out, opening the door for several shortwave passages within the 500 mb wave train. However, overall rainfall amounts should be held to a minimum with high pressure in the area and lack of forcing mechanisms at the surface.

Temperatures... Arctic high sliding south in the wake of the front Monday into Tuesday will bring about a spell of below average temperatures during the middle of next week, with highs only getting into the mid 40s to mid 50s. However, cooler temperatures will be short-lived as return flow sets up on Wednesday, warming highs back up into the 50s and 60s. Monday night lows will fall into the low to mid 30s across the north, though little to impacts are expected since the growing season has come to an end.

Aviation

for 00Z TAF Issuance Issued at 637 PM CDT Thu Oct 22 2026

Stratus far northeast WI to lakeshore slowly expanding west. Thus far, vsby are unrestricted, but with evening cooling do expect that to change. By late evening, expect dense fog to develop with cigs and vsby less than 1/2SM at times. The fog will be most dense from the Fox Valley to the lakeshore, including GRB/ATW/MTW. Conditions may drop below airport minimums at times. Patchy fog possible elsewhere, down to IFR at times late tonight. Once the fog forms, expect lower vsby to persist through 12-14z Friday, with lingering stratus 14-16z Friday. VFR conditions should return to the entire area on Friday afternoon. With high pressure overhead, winds will be light under 10 kts through the TAF period.

Grb Watches

None.