Forecast Courtesy of: Paulge
The Global Weather & EAS Society Discord: join the conversation on this evolving outbreak situation.
Summary
Another potentially significant tornado and severe thunderstorm outbreak is expected across the southern and central Plains region as a very potent low pressure system over the eastern Four Corners pivots east.
Very strong forcing alongside ample moisture and building instability will generate favorable conditions for an outbreak of severe thunderstorms, with numerous tornadoes and instances of very large hail and damaging winds expected.
SOUTHERN GREAT PLAINS
You might want to fasten your seatbelts for this.
As the low pressure from the Desert Southwest walks its way over eastward, it will pull two key ingredients:
- surface dewpoints in the order of 65-70 degrees Fahrenheit, which seems to be evident as the dryline is moving north and westward as of 0700 UTC
- a strong 60kt low-level jet coupled with a 75 (RAP) to 90 (SPC Outlook) knot mid-level jet
With this, instability in the order of 2,000-3,000 j/kg of MLCAPE (up to 3,500-4,000j/kg towards the evening near the dryline) will easily overspread the region, alongside ample bulk shear for supercell creation (0-6km at 40-50 kts). Very large hail will be a major concern when mixing these ingredients.
Tornado Risk
Now, for the tornado risk. You can’t really sugarcoat this, it’s going to be bad, but there’s still some uncertainty.
0-1km Storm Relative Helicity will not be off-the-charts with any amount ranging from 200 to 300 m^2 s^-2 being common through the afternoon and evening hours. (It should be noted that recent model runs are hinted at narrow corridors where SRH may be upwards of 400 m^2 s^-2, however.)
This might not mean much. First, this level of SRH is still adequate enough for a substantial tornado outbreak given other factors. But more importantly, other factors when taking into account tornadogenesis, including an Energy Helicity Index (EHI) levels that will generally exceed 3.0 in the more favorable tornado areas. Second, the atmosphere is generally expected to recover quickly from any morning convection. This will make growth easier for severe cells and, should clearing happen soon enough, be sufficient conditions for violent tornadoes.
Uncertainty
Of course, there is uncertainty about how much the morning convection clears out. If there’s too much or it doesn’t clear sufficiently by the mid-afternoon, the tornado threat may be more isolated or conditional. There is also the possibility that a warm upper layer may inhibit growth unexpectedly.
Barring these two conditions suppressing storm growth, though, a significant tornado outbreak should take place. Check back during the daytime for any updates on the progress of this weather regime.
CENTRAL PLAINS – REST OF KANSAS, SE NEBRASKA, SW IOWA, AND W MISSOURI
Severe thunderstorm development should also start relatively quickly here, without much influence from any morning convection. An area of very high MLCAPE will overspread eastern Kansas through the early afternoon, sufficient by itself alongside the approaching system to produce severe thunderstorms.
Low-level SRH values are expected to be quite less impressive than in the southern Plains (average values of around 150-maybe 200 m^2 s^-2), and by the time better SRH arrives, convective inhibition from earlier thunderstorms should have overspread the region.
However, a close LFC-LCL height ratio suggests tornado potential is still evident over eastern Kansas. Finally, sufficient bulk shear in the order of about 35ts should still warrant supercell production, and combined with the profiles mentioned above, tornadoes will still be a concern.
Severe thunderstorm threats, including damaging winds and large hail, should also be a concern for this area throughout the afternoon and into the evening hours.
