The Storm Prediction Center (SPC) has issued a Slight Risk for the southern Great Plains today.
Associated with the Slight Risk is a 2% Tornado Threat ring.
The 12Z upper air sounding from Midland/Odessa, TX, does not look much like a severe storm sounding. There is very little Convective Available Potential Energy (CAPE), and plenty of Convective Inhibition (CIN).
The hodograph tells the tale of non-rotating storms; low-level shear is good (20 kts), but deep-layer shear is weak (23 kts).
The 12Z upper air sounding in Amarillo, TX, is even worse; lower CAPE, lower shear.
The visible satellite imagery shows that clouds are clearing from the Slight Risk area. This will maximize diurnal heating and perhaps raise the CAPE through this afternoon.
The water vapor imagery shows a clear shortwave trough dipping through the Rocky Mountains, moving east, placing it directly north of the Slight Risk area.
The 300 mb NAM chart for 0Z Saturday (this evening) shows that this shortwave is not forecasted to be strong; there is only a weak speed maximum that will pass north of the Slight Risk area.
The 500 mb NAM shows that below the speed max (both in altitude and latitude), there will be some Positive Vorticity Advection (PVA) moving into the Texas Panhandle from southeastern Colorado. It is not a very sharp gradient, but it will boost convection.
The SPC Mesoscale Analysis surface pressure map and RAP model show a low pressure system developing over western Texas. It is currently 1010 mb, and expected to drop to 1008 mb in the next few hours.
The surface analysis map shows that winds are light, and dewpoints approaching 60 F over the threat area. There is moisture present, though surface advection of moisture into this area has decreased considerably from a few days ago. A strong dryline is established just east of El Paso, TX, and cuts through eastern New Mexico, with dewpoints in the 30s on the dry side, and upper 50s and 60s on the moist side.
CAPE is currently lacking in the Slight Risk area. CIN, however, is not. There is a pocket of CAPE exceeding 1000 J/kg over southeastern New Mexico.
According to the RAP, this CIN will erode away, and CAPE will increase with diurnal heating. By 18Z, the map will be mostly clear of CIN, and a small area of 3500 J/kg is possible just inside the Texas border.
The Effective Bulk Shear is unimpressive this morning, with less than 20 kts available in most of the Slight Risk area.
The RAP shows this increasing in a from the south in a plume to over 30 kts by 20Z. This is marginal for rotating storms, but there is some threat.
LFC heights are large across the Slight Risk area right now, sometimes exceeding 4000 m.
Conditions look marginal for storm formation. There is little incentive for a parcel to rise (currently), though that will increase throughout the day. The deep-layer shear is weak, though that is expected to increase as well, but only to marginal levels.
On the other hand, anvil-level winds, 500 mb level winds, 700 mb level winds, and so on blow directly away from the dryline, and will perhaps move faster than the dryline, meaning storms that form will outrun the boundary. If they do form discrete supercells, they will remain discrete, as long as they can outrun the dryline, even into less favorable environments. However, if the dominant force today is the dryline, and the CIN really melts away as fast as the RAP is predicting, I expect a blobby mess with perhaps an embedded supercell, at best.
I think I’ll sit this one out today and work on my car. It isn’t to say that storms aren’t possible; stay tuned to the National Weather Service (NWS) radio. I will not be chasing them today, however.
I am watching next week, as this may be my last week to chase this year.
Thank you for reading my prediction.
The Severe Weather Outlook is from the Storm Prediction Center website.
The satellite imagery is from the NOAA Satellite and Information Service.
The surface observation and upper level charts are from Unisys Weather.