Good Saturday morning to you,
Yesterday was a heavy action day in the Great Plains with a large variety of forcings at play. The Denver Metro has all but shut down on the receiving end of 1.5′ snow with as much as 4′ expected in the surrounding area. The snow is largely confined to the NW quadrant of the Low Pressure and results from moist Caribbean air carried aloft and Westward by the Cold Conveyor Belt.
Meanwhile in the warm sector, tornado watches were in effect through most of the day. There were three main regions of activity.
1)Squall lines with large hail ripped through Northern Texas and Oklahoma with the primary activity falling along the Oklahoma’s southern border, East of the pan handle. What started with Tornado watches ultimately lacked in wind shear. Due to largely unidirectional winds we saw individual cells converge into squall lines which manifest their convective potential in the form of damaging hail with reports of stones up to 2″ in diameter.
The lifting mechanism and organization for these squall lines lies in the frontogenesis occurring at the cold front of the developing low pressure system. The more wispy precipitation seen in the radar loop over central Colorado indicates heavy snow fall carried powered by the the Cold Conveyor Belt as discussed w/r/t the Denver region creating a cloud head. This cloud head, together with the frontal feature, account for the formation of the characteristic comma shape of a mid latitude cyclone.
2) While the border was spared there were multiple a super cells around the Texas Louisiana border with a possible touchdown in Burleson, TX. The damaginig winds from these cells reach an estimated 60-70mph and was responsible for downed trees and power lines across parts of Texas, Arkansas, Louisiana, and Mississippi. This Skew -T from Lake Charles, LA demonstrates the general characteristics of the area.
The key features of this graph are
a) over 2000 J/m2 convective available potential energy – or, simply put, plenty of storm potential.
b) significant wind shear from the surface to 500 mb. This is what distinguishes the Eastern Texas events from the Oklahoma linear convection.
c) Strong convection up into the middle troposphere is already underway as evidenced by the saturated environment to 500 mb.
Here, we see 2 supercells that spawned twelve hours apart under similar conditions earlier in the day over Eastern Texas. The first was in Burleson, TX where a tornado touchdown was reported. The second was to the South and East nearer to the Louisiana border.
3) Finally, the area of activity occurs over central Missouri. Weak frontogenesis is coupled with Trenberth forcing to initate intense vertical motion. As the Thermal wind flows perpendicular to the strong temperature gradient at the warm frontal region of the developing cyclone.
All of these events took place within the developing low pressure system in the Great Plains. Above is the liquid equivalent precipitation predicted totals. It is expected to persist into the weekend bringing rain and snow along the way. The final snow totals are in with 20-50″ in the hardhit parts of Colorado. Nebraska saw any where from 11-20″ along the storm track and western Iowa is already recording up to 7″ as the system approaches Des Moines later tonight.
The Low will track South of Wisconsin, close enough to have a share of the cloud shield, but limited flurries above the North of the Illinoisborder. High temps will be slightly above average and stable into the upper 30s this weekend falling to the upper 20s overnight, with a return to sunshine and temps in the 40s by early next week.
While things may be uneventful here at home, I’m glad we could share in the action!
Thanks for checking in at MadisonWx. Stop back next Friday as we turn our eyes to the local scene for the coming week.