Low pressure centered just east of Lake Huron in the southernmost portion of Canada's Ontario Province will continue a slow eastward movement the next 24 hours. At the same time, a large elongated ridge of high pressure extending all the way from Canada's Hudson Bay south through the plains to Texas will move east toward the Mississippi Valley. As a result, the tight pressure gradient that has produced the very strong northwest winds on the back side of the Low pressure system will very slowly loosen - and winds while still strong this afternoon into tonight will begin to become northerly and then a little east of north by Saturday morning.
Very cold air remains aloft, and for Chicago this will mean considerable instability cloudiness along the Lake Michigan shoreline and out over the warmer lake with a chance of more shower development. Winds in this area will still gust well in excess of 30 mph with considerable wave action continuing. The farther inland you go this afternoon, the more scattered the cumulus and stratocumulus clouds will become along with northwest winds 20 to 30 mph and high temperatures in the mid to upper 50s.
As winds become more north to northeast tonight and Saturday morning, the showers over the lake will drift west and perhaps move a little inland right along the Illinois Lake Michigan Shoreline while continuing over northwest Indiana. It gets tricky farther inland toward the Fox River Valley and west, where skies should clear tonight and winds diminish. The temperature drop off in this area after midnight toward Saturday morning will depend upon how far inland the clouds drift. Should the clouds stay close to the city and shoreline, readings could fall into the 30s in outlying areas with frost in some of the colder frost-prone locations.
