Valley under dense fog advisory tonight

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Much of southern Minnesota and western Wisconsin are under a National Weather Service dense fog advisory from 10 p.m. tonight through 10 a.m. Wednesday. An approaching cold front is expected to bring showers, thunderstorms and much cooler air to the region Wednesday and Thursday.

Storms, colder air poised to move in region Wednesday

The St. Croix Valley is under a National Weather Service dense fog advisory from 10 p.m. today through 10 a.m. Wednesday.

An unseasonably moist air mass across Minnesota and Wisconsin will allow fog to spread over the area tonight, according to the NWS forecast.

“The fog will begin to rapidly expand across the area after 10 p.m. with widespread visibilities of a quarter-mile or less expected after midnight,” said an NWS statement. “Dense fog will create hazardous traveling conditions due to significantly reduced visibility.”

NWS forecasters said fog would dissipate across western Minnesota early Wednesday morning as a cold front approaches from the Dakotas.

“The fog will persist into the mid-morning across eastern Minnesota and western Wisconsin.

That approaching cold front is expected to trigger a chance of showers and thunderstorms beginning early Wednesday afternoon, with storms developing after 4 p.m. Wednesday. Precipitation chances are 60 percent with rainfall amounts ranging from one-tenth to one-quarter-inch, with heavier amounts in thunderstorms.

There is a 90 percent chance of thunderstorms Wednesday night with one-quarter to one-half inch rainfall possible. Winds will shift to the north-northwest at 8 to 17 mph, with gusts up to 25 mph and temperatures dropping to the low 40s.

Thursday will be damp and blustery, with showers possible into the early afternoon. Highs will struggle into the mid-40s with northwest winds 13 to 18 mph, gusting up to 26 mph.

Thursday night will be partly cloudy and chilly with lows falling to the upper 20s, but winds diminishing to 5 to 10 mph. Friday will see cool sunshine, with highs in the low 40s.