The Storm Prediction Center (SPC) has issued a Moderate Risk in a tight bull’s eye in Wyoming.
Associated with the Moderate Risk is a hatched 15% tornado threat ring.
The 12Z upper air sounding from North Platte, NE, shows a rich storm environment, though it is capped. North Platte is downstream of the Moderate Risk area, but it does show plenty of moisture available, provided it will advect towards the threat area. This environment shows 2251 J/kg of Convective Available Potential Energy (CAPE) and -251 J/kg of Convective Inhibition (CINH).
The hodograph shows that the shear is weak, with only 7 kts of low-level shear, and 18 kts of deep-layer shear.
Synoptically speaking, the 300 mb NAM shows a shortwave trough ejecting into the threat area today.
The visible satellite imagery shows some mountain-wave pattern, which indicates a little additional horizontal shear.
The surface observations show the east and southeasterly winds that are advecting moisture into the risk area this morning.
The surface pressure chart shows that there is a low that is moving to the east and northeast. The low will help boost the southeasterly winds, and will put Wyoming in the warm sector.
The NAM shows a nice dryline bulge by 21 Z. The dewpoints are not high by Texas and Oklahoma standards, but are more than adequate for Wyoming and western Nebraska.
The NAM also shows that the SigTor parameter is looking good in eastern Wyoming as well.
For what it is worth, the HRRR shows helicity tracks moving to the northeast.
This would still be a very difficult chase. This chase terrain lacks roads, but it does have hills. Chasing here would involve starting in Wyoming, with hills and a limited road network, and would end somewhere in the Nebraska sand hills.