Tomorrow kicks off my 2014 storm chasing trip from Denver, Colorado. Today I'm traveling to Denver from Louisville and keeping up with weather data as I go along. The reason our storm chasing group (Storm Chasing Adventure Tours) is based out of Denver this time of year is because the severe storm threat generally moves northward later in spring. Early spring storms tend to be in the Southern Plains, which is why earlier tours are based out of Oklahoma City.
Right on cue, the storm threat lately has shifted toward the Central and Northern Plains. Tonight a shortwave trough aloft will move from the West Coast into the Rocky Mountain region, generating some faster southwest winds at about 18,000 ft. As the sun rises over the High Plains tomorrow an area of low pressure will develop in Eastern Colorado in response to the trough aloft moving in over the mountains. The process by which this happens on the eastern side of the Rockies with upper-level lift and wind support is called lee-side cyclogenesis. As this is all happening a cold front will be moving in from the north, complicating the setup a bit.
Where we travel to tomorrow will likely be dictated by where the greatest wind shear sets up. Right now that looks like somewhere near the central part of the Kansas/Nebraska border given the easterly surface winds that both the NAM and GFS models have there with the tightening low pressure, but then in Southeastern Colorado. These easterly surface winds increase low-level shear, and thus the chance for rotating supercell thunderstorms and tornadoes. Should that low not tighten as much the easterly winds might be positioned a bit north. In any case, it looks like there will be enough moisture, instability, and a dry air push from the west (helps to generate lift) for storms to get going. Overall wind shear (the difference between surface winds and those aloft) is a little weak, so the tornado threat doesn't look all that big. It is there though since we do have the prerequisites for it in other categories. I'm also concerned that these supercell storms will blob together into a line of storms later on in the evening. How fast that happens will determine how long we'll be able to chase them since it's much more difficult to chase a line of storms as opposed to individual stronger supercells. Hopefully this process will wait until well past sunset when we'll be done chasing anyway. We'll evaluate the data in the morning and make a final decision then. The Storm Prediction Center (SPC) has issued an upper-end 30% Slight Risk due to the severe weather threat, which is an upgrade from yesterday's 15% risk that was issued.
It looks like Monday and Tuesday could be active chase days as well. The SPC has a 5% severe risk over parts of the Central Plains on Monday, which could get updated to a Slight Risk per their latest discussion. There's also a risk outlined in Nebraska/Kansas on Tuesday. Hopefully we'll have some good storms to chase!
Ryan Hoke