While the National Weather Service issued a Winter Storm Warning early this morning for Lake County, current forecasts indicate that there may be less snow than originally expected.
We have just participated in a conference call with the Chicago office of the NWS, and are providing this update regarding the winter storm expected to impact us later today through Thursday.
A strong low-pressure system now in the southwest part of the United States is forecast to organize further and develop rapidly near the Texas panhandle, then move quickly northeast toward southern Lake Michigan. The central intense low-pressure with this storm is expected to be similar to a Category-3 hurricane in the Atlantic Ocean. As with many winter storms, forecasting the location and movement of the boundary line between rain and snow is the biggest forecast challenge for this storm.
Heavier precipitation is moving into western and south-western Illinois now. North of Interstate 80, precipitation is expected to start later this afternoon as snow, maybe with some sleet mixed in, and bursts of intense snow are likely for a few hours. The rain/sleet/snow line will start out southeast of Chicago, and will progress slowly northwestward to the northwest suburbs over the evening hours. Temperatures will rise very slowly during this time. With the current forecast storm track, nearly all of Lake County is expected to see precipitation change over to or mix with rain, which will significantly reduce probable snow accumulation. There is substantial moisture with this system, so heavy rain is possible.
Across Lake County, during the period of intense bands of snow, from roughly 4 pm until 8 pm today, we could see a couple of inches of snow, but the ground surface temperature will likely not be below freezing. Some melting of this snow is expected, and while the bands of intense snow will impact traffic, roads are not expected to become unusually hazardous. Through the evening, gusty winds from the east will increase to around 20 mph with gusts to 40 mph possible, and the atmosphere will be capable of supporting isolated thunderstorms or even thundersnow overnight. Thunderstorms that occur will locally cool the atmosphere, so the transition from snow to sleet to rain will be neither linear nor consistent. Most locations in the county should expect to see a sloppy mix of precipitation with alternating periods of snow, rain, and sleet.
Wednesday morning, as the storm system moves on to the northeast, the winds will shift to come out of the west. This strong west wind, sustained 25 to 25 mph with gusts of 45 mph possible, will bring colder air to the region. There is a possibility of some localized wraparound snowfall on Wednesday morning, and depending on the temperature, any snow that falls Wednesday morning may blow and drift in the increasing winds. Once the wind changes direction sometime Wednesday morning, temperatures will drop steadily, reaching lows near zero (or below, in areas where snow remains on the ground) on Thursday morning. With sustained 20 mph or stronger winds and actual temperatures near zero, windchills of 20 degrees below zero are possible Thursday morning. Temperatures are expected to rise slowly by only a few degrees during the day Thursday, but winds will diminish.
While current snowfall forecasts are less than warning criteria, the NWS forecasters have indicated they do not plan to drop the Winter Storm Warning because projections are still based on the forecast track of the storm, and any deviation from the forecast track could lead to increases (or further decreases) in expected snowfall.
With the expected very cold temperatures and strong winds, folks need to bundle up well and avoid spending time outside, particularly on Thursday morning. Hypothermia can develop quickly, so staying out of the wind and dressing with layers are important protective actions. Young children and the elderly are more susceptible to Hypothermia.
We do not anticipate providing any further update messages about this weather system.
