Sunday, November 16, 2014

Another winter weather event tonight - this one NOT a surprise

Another Arctic cold front moves through the Mid-South overnight, dropping temperatures as precipitation moves out behind a low pressure system moving through the southeastern states. This is a familiar pattern for meteorologists. The timing of the arrival of cold air and departure of deepest available moisture always creates an interesting scenario for wintry precipitation in the Mid-South.

A Winter Weather Advisory (purple) for up to 1-2" of snow is in effect for counties just north of the metro overnight. 
In this case, it appears there will be some light precipitation as sub-freezing air moves into the region, mainly in the lowest 5,000' or so of the atmosphere. Though surface temperatures won't reach freezing until 4-5 am, we expect that the low level (above surface) temperatures will drop below freezing as early as midnight. Meanwhile, precipitation looks to linger until around 6am.

High-resolution Rapid Refresh (HRRR) modeled precipitation & type from 11pm-5am tonight. Notice the bulk of the rain is east of the metro, however a brief changeover to rain/sleet (pink) occurs around midnight, followed by light snow.

Bottom line forecast

Short term models are in good agreement with this system. Light rain showers, drizzle, and mist continue this evening with temperatures well above freezing. One last round of steadier (though still light) precipitation will arrive by 10pm-midnight, changing from light rain to a rain/sleet mix for a couple of hours before becoming all snow (still very light). By the start of rush hour, almost all light snow will be east of the metro with flurries lingering through rush hour. Winter precipitation amounts will be under 0.10" total.

Impacts Expected

Even though all precip ends around rush hour, temperatures will fall below freezing by 4-5am, reaching the upper 20s by 7-8am for the morning low. Given the issues that occurred Thursday morning with about 0.04" of sleet/snow, I would expect you'll need to take potential icing of bridges and overpasses into effect in the morning. Check your favorite traffic source before heading out (I highly recommend the traffic layer on Google Maps that color codes roadways based on traffic speed and plots all known accidents). Give yourself PLENTY of extra time and drive carefully! Quick stops, starts, or land changes on elevated surfaces is a recipe for disaster. By mid to late morning, things should improve rapidly due to gusty wind (an evaporation aid), some sunshine, and tire heat on the roads.

Extended outlook

Temperatures will only top out in the mid 30s Monday with wind chills in the 20s all day. The coldest air of the night arrives Monday night with lows in the teens metro-wide and wind chills at the bus stop Tuesday morning near 10. Mid 30s highs are expected again on Tuesday before a warming trend commences Wednesday with a high near 50. Click here for the complete MWN Forecast.

Erik Proseus
MWN Meteorologist

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