Wandering the High Plains
Today’s storm prospects are focusing in on eastern Colorado into southwestern Kansas, as an area of low pressure spins over the Front Range. Climatology says that northeastern Colorado is the tornado hotspot of this region, but relatively modest boundary layer moisture in this setup has my eyes set a bit farther south.
Recent trends in observations and short-term model data show that a triple point-type setup may evolve this afternoon in southeastern Colorado, where a warm front and dryline intersect with a surface low. This is evident in model simulations, where a bulge is noted on surface charts and convection allowing models show robust storm development. This leads to increased confidence in targeting the area for a storm chase. The main concerns will be large hail with this development, given favorable deep layer shear and seasonably large CAPE (instability) profiles. Cloud bases should start off fairly high and with meager low-level shear, this is not an apparent tornado setup. With that said, toward sunset, as cloud bases lower, boundary layer moisture improves and low-level shear increases dramatically, there is at least a conditional threat for an isolated tornado. This would most likely not happen in southwestern Kansas around 00-02z (7-9 p.m. CDT) and this scenario hinges upon storms remaining isolated. If convection is too abundant, the resultant messy storm mode would limit the threat for any dominant, discrete storms.
Realizing that any tornado threat is relatively limited, the expectations today will be for storm structure and perhaps a long-lived, robust thunderstorm crossing over from Colorado into Kansas. One cannot completely discount the northeastern Colorado/Nebraska panhandle area, but storm modes look fairly messy up there, as a line or cluster of storms should evolve by 00z. Farther south into the panhandles, boundary layer moisture looks even more favorable, but weaknesses in the mid-level wind field cast some uncertainty around supercell thunderstorm development, or at least longevity of. While the Dakotas target has long been discounted for logistical reasons, seasonably significant moisture, coupled with a warm front in the area suggest that a tornado threat also exists in the northern Plains.
