and 16th. With this system, it was not your typical setup. Normally for a winter storm in Arkansas, you need cold air either coming in or retreating and a storm system riding along or near the Gulf Coast. This supplies our moisture source to aid in the formation of precipitation. Without it, we are at the mercy of the arctic air. This proved to be the case this night. However, amidst all the snow falling, there seemed to be a cutoff zone where the air was to dry to produce anything. This is known as the cutoff zone. Where you will see several inches in one part of a county and only a trace to maybe nothing at the other end of the county. This was one of the most unique setups i have seen for sure. Instead of the typical low pressure snow, you got a cold front with moisture developing behind it in the cold air, a 500mb vort max (strong trough) pushing across the state aiding in lift needed for snow production, and an 850mb trough getting hung in the Ozarks,keeping the driest air at bay for a little while until it finally won that battle. Only a few flakes flew in the River Valley with up to a half a foot in southeast Arkansas. I wont go into all of the meteorological terms as to why this happened but I will give you the thoughts as to why it did.
The day of the snowfall, we went through a period we often refer to as compressional heating. We sat between a high to our east and a front to our north. The result? For Central and south Arkansas was warming temps with increasing moisture. Most topped out in the 50s and even a few 60s! So your last thought was snow at that point. But in the north, the cold front was hard at work with falling temps and snowfall. It was this initial band that developed that dropped more than 6 inches in Mt. Home. This band was originally moving west to east along the front. The front left the snow behind and continued to move south. This left behind the 850mb front which was the eventual dividing line between the dry air and the snow later that day. Also would be the added lift needed for snowfall across the southeast.
Here is a snapshot of what the radar looked like on the evening of MLK Day. Snow ramping up to the north and rain south in the warmer air. if you notice in the circled area, a band of snow was developing along the 850mb front as it started to drop southeast into the state. Snow was reported in most areas in blue, however dry air was undercutting the moisture making it hard for more than flurries in the river valley. A dusting was reported in higher elevations. In Northeast sections, snowfall was reported moderate at times.
The cold front was rushing southeast at this time with cold air rushing in behind it. The result was any rain, quicly turning to snow as the atmosphere mositure. In Fact, in Little Rock where the radar shown rain, the ground reports were sleet and snow. Also a good example as to why ground reports are so important.
Then we take it out another 3 hours. Temps had fallen a few degrees an hour with most places in central sections seeing snow and temps in the 20s. Snowfall was ramping up with a few moderate to sometimes heavy bands showing up on radar. This snapshot of the radar shows a band setting up to the northeast of Little Rock and one to the southeast of Little Rock. South Arkansas was still recieving rain at this time with changeovers just starting near Texarkana. The cold air was just starting to become entrenched. Even in that "heavier" band only a couple of inches would be seen.
To the northwest, you can see the lighter or even no radar returns. The 850mb trough was close enough to help with the lift near central but the dry air was cutting of people to the northwest. This cutoff is very hard to forecast ahead of time.
Now we take the radar out a few more hours. Here you can clearly see the dividing line between the haves and havenots. The southeastern half of the state was all snow with the northwest dry. The dry air was becoming more entrenched as temperatures continued to fall. At this point of the night, ratios for snowfall had exceeded to a 15:1 to 20:1 versus the typical 10:1 we normally see. What this means is for every 1 inch of liquid we would see 15 inches of snow. With only 0.01 to 0.08 amount of liquid only a few inches was seen.
The cold front did stall just southeast of Arkansas keeping the snowfall changeover a bit longer acorss the far southeast from starting. It also helped to keep the snow around a bit longer in parts of east arkansas and aided in a heavier band developing which resulted in the issuing of the warning furhter north for a bit more snow.
This is the last image I took of the radar Monday night. Dry air was rapidly moving into central Arkansas with snow ramping up across the southeast. In the red circled area, this is where some of the heaviest amounts of snow would end up being. This is where the right amount of moisture and lift would be realized and bit to the northeast as well. There was a sharp cutoff even here as dry air undercut the moisture. For example, parts of Camden only received 2" where others received up to 6". Very typical in this type of setup for sure. Dry air eventually cutoff the "heavier snow across areas north of 30/67/167 corridors not long after this with more being seen across the south. All of the snow was out of the state by mid morning Tuesday.
Remember as stated above no forecast is perfect and those higher amounts are impossible to forecast with the higher bands, but overall did the best job we did. Dry air is a snowfall killer, especially with deep, entrenched arctic air that we have seen this winter.
This wraps up this winter storm. Will there be more this winter? That will be talked about in a different blog.