Monday, December 15, 2008

Classic freezing rain setup for the Mid-South

Conditions have set up nicely for a freezing rain event overnight into early Tuesday morning along the I-40 corridor in the Mid-South. Surface temperatures have dropped as forecast and are now at or slightly below freezing across the area. The current temperature profile (going up in the atmosphere) has sub-freezing temperatures through the lowest couple of thousand feet, and then a pronounced warm layer (well above freezing) above that. Therefore, as moisture moves back into the region late this evening, it will fall through the warm layer, becoming rain, and then hit the cold layer. Some precip could form into ice pellets (sleet) prior to reaching the ground, but most of the precip will not actually freeze until it reaches the surface. Thus - freezing rain.

Fortunately (if there is a positive to this event), the amount of precipitation expected during the night in the metro area should be less than 1/4" based on the computer model that seems to have the best handle on things right now. This should limit some of the collateral damage from the ice (like power lines down, branches down, etc.), but will still create hazardous driving conditions late tonight and for Tuesday morning's rush hour, particularly on bridges and overpasses. Pavement temperatures (except bridges and overpasses) are running around 40 degrees right now, so it will take some precipitation falling on the roadways before they collect a glaze - bridges and overpasses are not this warm and will freeze first. Please exercise extreme caution if you must travel prior to about noon tomorrow, when temperatures will be back above freezing.

Be sure to stay up to date with the latest conditions and forecast at

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