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Wintry Mix Tonight
Snow remains possible on Monday

Jason Samenow @ 5:00 PM

Overcast skies have overspread the area this afternoon, holding temperatures in the mid and upper 30s. At 4pm, temperatures are generally in mid 30s and the air is very dry -- with dewpoints 10-15 degrees F. Meanwhile, a warm front is headed towards us from the southwest: setting the stage for a period of frozen precipitation overnight. And the potential for accumulating snow is still in the picture for Monday.

Tonight's Situation

As the said warm front approaches, precipitation will likely initially fall through some very dry air and not reach the ground. So don't expect much in the way of precip until after midnight. As the precipitation starts falling, the evaporational cooling will drop temperatures to around freezing (or a bit below freezing far and north and west), so be careful if you're on the roads after midnight. But the warm front is fairly potent, so while the air will support frozen precipitation at the onset, the changeover will happen quickly (by 4am in most areas).

  • Midnight-2am: A brief period of snow mixing with and changing to sleet and freezing rain. Temperatures 30-32.
  • 2am-4am: Mixed precipitation. Temperatures 31-34.
  • 4am-10am: Light rain. Temperatures 34-42.
  • 10am-5pm: Decreasing cloudiness, with highs near 50.
The far north and west suburbs could see 1" of frozen precipitation. Most areas may see the ground turn white briefly, before it's washed away.

I'm not expecting travel problems Sunday morning.

Storm Impact:
Travelcast (Sunday morning):

Monday's Situation

Overall storm assessment

Storm Impact:
Travelcast (for Monday night/Tuesday):
Schoolcast (for Monday night/Tuesday):

Last night, it certainly appeared the chances of a significant storm were on the decline. Now, it's not so clear. Most (not all) of the forecast models are back on board with the threat, although we're on the northwest side of the snow shield -- with the heaviest amounts to our southeast. Nonetheless, NOAA's Hydrometeorological Prediction Center believes we have about a 40% probability of seeing at least 4" of snow by 7pm Monday and we're on the edge of the 40% probability line for at least 8" of snow by 7pm Tuesday, with an outside shot (10%) of 1 foot or more.

It probably won't be until we're within ~24 hours of this event that we'll have a lot of confidence in the forecast. Although confidence should begin increasing incrementally, starting with my next update -- to be posted between 1 and 2 am tonight.

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