Forecast 5/17/18

A strong shortwave trough will continue to move across the Great Basin this afternoon, providing increasing southwesterly flow aloft downstream over the High Plains. The water vapor loop implies increasing forcing for ascent across the Southern Rockies with increasing mid/high clouds approaching the TX/OK Panhandles. Strong diabatic heating will allow scattered strong to severe thunderstorms to develop this afternoon and evening.

Fig 1. Increasing forcing for ascent noted over the Southern Rockies.

Rapid surface destabilization is taking place this afternoon with 18z KAMA RAOB indicating 700-500mb lapse rates of 9.1 C/km and surface temperatures near 90 degrees. The AllSkyLAP product suggests CAPE near 2500 J/kg with model progs increasing to near 3500 J/kg by peak heating. Deep-layer shear is a bit strong than previously anticipate with 0-6km BWD generally between 35-45 kts. This will be sufficient to sustain organized updrafts with some storms becoming supercellular initially before growing upscale into linear segments.

Fig 2. AllSkyLAP CAPE of 2000-2500 J/kg as of 1830 UTC.

Storms are expected to initiate along the dryline on the Caprock, moving in a general eastward direction. Lift may be enhanced across portions of the Panhandles by an outflow boundary originating from the ongoing convection over northwest OK. The Bunkers RM storm motion from the W and NW only 5-7 kts, suggesting a potential for heavy rainfall with any right movers. The very steep lapse rates and strong instability will support a large hail threat, with isolated sig hail reports possible this afternoon. There is also a potential for isolated damaging wind early in the storms' lifecycles, becoming more widespread as storms grow upscale.

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