A large and intense low pressure system, both surface and aloft, will form over the southeast US during the next 12 hours and then move to the northeast. From developing surface low pressure near the central KY/TN border tonight, the surface low will move to eastern lake Erie Tuesday evening and then up into Canada by Wednesday morning.
The Chicago metro area looks to sit right on the northwest edge of the precipitation. Far northwest sections will stay dry or a few sprinkles, to a cold soaking rain over southeast portions with rain amounts of 1 1 1/2” far southeast. The map on the left shows this very tight precipitation gradient during the next 36 hours right over the metro area. Before the rain ends, it is expected to turn to wet snow with a few inches of accumulation likely just to the east of the metro area over northeast IN into central and southeast MI.
The most noticeable item for all the metro area Tuesday will be strong NNE with gusts to 40 mph. These winds may produce some shore erosion and flooding along the lake MI shoreline in both IL and IN. In those southeast sections with the cold rain, the wind will make it quite nasty and will probably stress any umbrellas used to try to stay dry.
The normal high now is down to 41 and is continuing to rapidly fall. Highs Tuesday will be in the upper 30s, and then upper 30s to 40 for the rest of the week so mainly seasonal temperatures this week. A chance of a little rain or snow Thursday night and another chance of mixed precipitation Saturday night into Sunday.
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