Sunday, February 2, 2014

Sunday afternoon update: winter weather still expected tonight

5:30pm UPDATE:

An update to watches and warnings. All of the metro is now in a Winter Weather Advisory into the overnight hours.

3:20pm UPDATE:

** Ice accumulation remains the biggest concern as of this update. **

Temps have been sitting at 33.5-34.0 in the metro for the past couple of hours as precip continues to move across the region.  Areas north of the metro have been seeing wintry precip already, from northeast AR into the bootheel of MO and northwest TN.  These areas have been upgraded to a Winter Storm Warning for up to 1/4" of ice and 2-3" of snow/sleet.  In the metro, a Winter Weather Advisory has been extended until 4am for Crittenden, Shelby, and Fayette Counties, as well as adding DeSoto and Tunica Counties. Tipton County remains under an advisory until midnight.

Warning/advisory summary as of 3pm Sunday
Latest regional radar (auto-updating below) shows a lot of precipitation yet to fall as it moves southwest to northeast and the entire system moves east.  The back edge of the precip will move out of the metro from west to east between 11pm and 3am.

We're watching the freezing line slide slowly south and expect it to reach the metro between 6-9pm tonight (earlier north, later south).  This is when rain will become freezing rain and ice accumulation would begin. Some sleet could mix in with the rain up to a couple of hours prior to the freezing line reaching your location, but any early sleet will not be an issue as rain will wash it away and melt it.  After the temp hits freezing and until midnight or so, ice accumulation is expected to be in the 1/10-2/10" range for most under the Advisory.  By midnight, precip will be tapering off but cold air will overtake the warm layer of air in the lowest couple thousand feet of the atmosphere, changing freezing rain/sleet to light snow and/or freezing drizzle.  Total sleet/snow accumulation will be less than 1" on top of the ice and could be a dusting or less south of I-40.

Temps will fall overnight into the 20s, thus any ice/snow that falls after dark will likely still be around in the morning. Untreated roads could become slick this evening and still be that way in the morning IF the expected accumulations pan out. Be sure to exercise caution, especially on elevated roads, bridges and overpasses tonight and Monday morning, including after Super Bowl watch parties. Alcohol and ice don't mix! No pre-treating of roads can be done when it is raining, so all treatment will be as, or after, ice forms.

Posted at 6:30am Sunday:

Just time for a brief update this morning. For further details, please see last night's blog post.

The cold front has pushed through the Mid-South with temps in the mid 30s across the area at 6:15am.  The drop in temps will slow considerably now though with nearly steady temps expected for several hours. This will keep most precipitation rain through at least the morning hours and likely into the afternoon. However with temps a couple of degrees from freezing, warm air aloft, and a cold pocket just above the surface, ice will be possible, in fact likely, before all is said and done today.

By this afternoon, sleet will begin to mix in with the rain with initial reports expected to be in Tipton County and points north, shifting south into the I-40 corridor through the afternoon and into north MS by this evening. Only minor amounts of sleet are anticipated through sundown. By late afternoon/early this evening, temperatures will fall to freezing along the I-40 corridor, including Memphis and Shelby County, which is when rain becomes freezing rain mixed with sleet. By mid-evening this area could see precip change over to some snow and sleet as colder air aloft washes out the warm layer. Further south, north MS will see some sleet and freezing rain by mid-evening. All precipitation will taper off overnight, ending as very light snow or freezing drizzle.

Ice (freezing rain) accumulations will likely end up in the 0.10-0.20" range with snow and sleet overspreading the ice.  Ice is our biggest concern with this event. Snow/sleet amounts will likely range from an inch in Tipton County to a dusting to 1/2" in the I-40 corridor, to a dusting or less in north MS.  A Winter Weather Advisory is in effect for Tipton County now until midnight and for Fayette/Shelby/Crittenden Counties from noon Sunday until 6am Monday. North MS is not currently under an advisory due to the uncertainty of ice accumulation. Not enough snow will fall to reach advisory criteria. This may change later today based on latest forecasts.

Given the forecast, travel could become hazardous along the I-40 corridor starting early this evening, first on bridges and overpasses, then on secondary roads. Primary thoroughfares and interstates will likely take a few additional hours to become hazardous if they do at all. More hazardous travel will be found north of the metro starting later this afternoon while north MS is expected to have only minor issues, mainly during the evening hours.  With temperatures falling into the 20s overnight as precip ends, there will be no natural melting of ice or snow before at least mid-morning Monday. Travel could remain hazardous for the Monday morning commute. Plan ahead. We don't forecast school closings - those decisions will likely be made early Monday morning based on road conditions. Temps will climb to near 40 Monday allowing ice/snow to melt for most of the area.

We will have updated information throughout the day on our social media feeds, as well as via our forecast and radar products on our website and mobile apps (all links below).

-Erik Proseus, MWN Meteorologist
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