The above topographical maps highlight the interesting terrain that encompasses our area. Take note of the absence of precipitous variances in Northeastern Oklahoma versus North West Arkansas. Elevations throughout Benton County are right around 1200 feet plus / minus a few hundred and most of the area is rather plateau like, where as the Ozarks rise to some 2000’ plus / minus a few hundred in central Washington county and areas just south and eastward. Much of Northeastern Oklahoma is a continuation of the plateau with various rises in elevation throughout Cherokee and Adair County which are an extension of the Ozarks.

The latest runs of the NAM show an interesting correlation between these topographical variances and the shallow nature of the arctic air. Below are two model Thermodynamic soundings, the first of which is from Grove, OK.

This is off the 18Z run of the NAM and is the "proposed" thermal profile of the atmosphere directly over Grove.The red line on the right is the temperature profile and the black dashed is the dew point. In this particular sounding the atmosphere is nearly saturated through 700mb or roughly 10,000 feet. Of particular interest though is the slope of the sounding from the surface upwards to about 940mb. This layer, from the surface up to roughly 480 meters or 1575 feet, is below freezing temperature wise. This is what the dreaded “freezing rain” looks like on a Skew-T chart.

Fayetteville’s sounding looks like this off of the same model run. Note how temperatures from the surface to nearly 700mb are entirely above freezing. This is the profile of rain, but interestingly the temperature does fall from the surface through the first 10-20mb (250-500 feet) or so before beginning to rise.

After perusing many of these soundings today throughout the entire region, there is definitely a deeper layer of cold air prognosticated to move in over the relatively flat areas of NE OK and westward, stretching into the flatter areas of NW AR.

The mountains may indeed hold up the colder air until late in the weekend when the layer of arctic air becomes deeper. Higher terrain typically known for wintry precipitation will be above the cooler denser air and it's likely that a rain event will initially unfold, going over to a mix sometime on Sunday. Another day of assessing the leading edge of the cold air through real data and making the comparisons with hopeful model consistency should continue to fine tune the forecast.