Chicago, IL

Chilly Winds are Forecast for the Chicago Area Today; Freezing Level Temperatures are Expected

Bryan Dijkhuizen

In the early morning hours of today morning, a 1035 Mb surface high peeling away to the east and eastward into the lower Ohio River Valley, with the accompanying ridge axis bisecting the local forecast region, was discovered.

The pressure decreases are still occurring over the Dakotas and Minnesota, and they are part of a larger zone of lower-level warm advection that is making its way eastward across the region today.

With a tightening pressure gradient following our departing high and some momentum transfer from an extremely impressive low-level jet core, we can expect a blustery/brisk day as south-southwesterly gusts pick up in the afternoon.

Because of the chilly start and a crusty/iced-over snowpack, there is some doubt about how powerful the gusts will be today.

This will likely influence the depths of the boundary layer. During the afternoon and early evening, we should see wind gusts of approximately 30 mph or so developing regularly, with some gusts reaching 35 mph at times.

Even though we'll be warm advecting today, the winds will most likely make it seem everything but warm. High temperatures will attempt to get closer to the freezing level, but daytime wind chills will mostly remain in the teens to mid-20s, according to the forecast.

Later this evening and tonight, the winds will gradually subside.

The most significant change for Wednesday was the introduction of some lower-end possibilities for snow and rain, mostly for areas along and north of I-80 and in the Midwest.

According to the guidance, a very energizing mid-level impulse will sweep in throughout the Midwest and Great Lakes area during the day on Wednesday, with a core of at least moderately steep mid-level lapse rates.

The primary source of model discrepancy at this time seems to be the extent to which lower-level saturation occurs before this impulse, according to the data.

The existence of at least periodic waves of more cohesive/intense isentropic upglide inside the more unstable layers aloft implies the possibility of introducing a small risk of a cyclonic storm developing.

With PoPs, we are beginning to get somewhat stronger ensemble support for at least light precipitation skimming the area, with the greatest signal along and north of the Wisconsin state boundary and along and north of the Minnesota state line.

Because they maintain a modest warm nose in place immediately off the surface, some thermal profiles from some guidance suggest the possibility of freezing rain, but most soundings indicate that snow will begin before the low-levels warm sufficiently into the afternoon to turn things into more of a rain/snow mix.

Since there is at least some potential for a light coating of snow, or slick travel if the wintry mix scenario pans out, across parts of northern Illinois, especially if precipitation gets started early enough in the day on Wednesday, we'll keep an eye on this system, but confidence in too many elements remains too low for us to get more specific on the details at this time.

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