Monday, March 25, 2013

One Good Thing About Spring Snow

It's March 25th and the weather headlines look like they should be dated December 25th. Ground zero for Day 3 of this storm was an area from east-central Missouri through central Illinois. There was an initial burst of snow early Sunday morning that left up to 3 inches of snow in some locations, followed by several hours of no precipitation. In many areas the snow that fell overnight melted off as temperatures rose to the mid-30s. By late morning and early afternoon Sunday heavy snow was quickly spreading eastward across Illinois.

The Mesoscale Convective Discussion graphic at
11:52 a.m. CDT March 24 from the Storm Prediction Center
The atmospheric conditions were set up for a sustained heavy snow event. Low pressure was moving slowly eastward though southern Missouri, and warm, moist air aloft was streaming northward. This  combined with instability and strong upward motion in the atmosphere to produce the heavy snow. Thundersnow was reported at a number of locations from St. Louis into central Illinois. Snowfall rates of 2 to 2.5 inches per hour occurred over a sustained period, and the result was widespread snowfall of 8 to 12 inches, with a number locations west and northwest of Springfield, IL reporting 15 to 18 inches of snow. The CoCoRaHS Observer at IL-SG-17 (Springfield 4.4 W) reported 16.5 inches of snow. This was a heavy wet snow, with snow-to-water ratios on the order of 9 to 1 (9 inches of snow to one inch of water).

48 hour snowfall accumulation map through 7:00 a.m. March 25 for central Illnois

Snow from this system also piled up from Indiana through southern Ohio and northern Kentucky to West Virginia. The storm still has a little punch left tonight, with Winter Storm Warnings in effect for the central Appalachians.

72 hour snowfall accumulation through 7:00 a.m. March 25
There is one good thing about a late spring snow, especially if you are tired of it. The higher March sun and temperatures above freezing quickly melt the snow on pavement reduce the snowpack. By late afternoon today where I live roads were mostly dry and you could tell that there already was a significant reduction in the depth of snow on the ground from the 10 inches I measured this morning.The hazard the next couple of nights will be refreezing of melting snow on roads as temperatures drop into the 20s overnight.

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