Wednesday PM Update: Winter Weather Advisory Through 8am Thursday

The National Weather Service has issued a winter weather advisory for the urban corridor as low cloud cover and fog bring a threat of ice to the Front Range and plains through Thursday morning.

Freezing drizzle setups usually occur when there is a very shallow sub-freezing layer near the surface with a "warm nose" atop that. This saturated layer in the lowest portion of the atmosphere is composed of supercooled water droplets that freeze on contact with the surface.

Although this sounding is from 5 AM this morning, we can see the shallow moist and sub-freezing layer in the low-levels, with dry air atop that. Since the air is so dry right above the surface, implying the lack of mid-high level clouds, we are unable to seed and feed snowflakes down into the low-levels, where these supercooled droplets can stick to snowflakes being transported down to the surface (accretion is the scientific term).

As of 3pm, freezing drizzle and freezing fog was reported at DIA where arriving flights had been delayed. Other areas of icing reported to the north near Loveland.

The biggest impact of this system will be overnight through 8 or 9am Thursday morning. That's the timeframe of coldest temperatures which clearly make it easier for ice to form on roadways, surfaces, etc.

The low cloud cover and freezing fog will be around through the night until attempting to lift a bit Thursday midday and afternoon. So long as the visibility is reduced there will be a threat of ice on all surfaces.

Drivers should be aware of the potential threat and take their drive a bit slower. There won't be much in the way of snow for the state with this particular setup, with just a dusting in a few spots, and perhaps a few inches at the highest elevations across the northern mountains overnight:

Other than dealing with some icing concerns tonight, the other main story will be the much colder temperatures that have been in place all day today and will remain so tomorrow, as compared to recent days. Temperatures are in the 20s now across eastern Colorado, more than 30 degrees colder than this time yesterday:

Thursday remains chilly with highs near 40 for Denver before we begin warming things up for the weekend. Right now, both Saturday and Sunday look to be very nice with highs back in the mid to upper 50s in Denver.

Brendan Heberton

Brendan is founder of Weather5280. He is co-founder of FreshyMap, and develops software for geospatial data analysis and visualization.

Denver, Colorado
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