Summary
A very active and significant four day severe weather sequence is forecasted for portions of Iowa, Missouri, Nebraska, Kansas, Oklahoma, and Texas. Additional severe threats exist with lesser certainty in Arkansas, Illinois, Wisconsin, and Michigan. A very large hail and conditional tornado threat exists today across parts of the Great Plains ahead of a sharp dry line.
Day 2/Friday features a stronger tornado threat, should storms form further from the exact location of the low pressure system, alongside large hail and damaging wind gusts.
Day 3/Saturday has the potential for a significant, higher-end outbreak of strong tornadoes.
Today (Nebraska, Kansas)
Supercell thunderstorms are almost certainly able to form this afternoon over NW Kansas, SW Nebraska and parts of NE Colorado ahead of a potent 500mb shortwave.
Moisture is quite evident already across the risk area, with surface dewpoints exceeding 60F. Given this, even with strong solar insolation, vertical mixing will not be an issue and conditions will be favorable for supercells with fantastic available instability and strong forcing alongside excellent flow (60kts at the 500mb level).
Very large hail will be the main threat, though a strong tornado or two are possible until convective modes become very messy.
Today (Texas, Oklahoma)
While the ceiling is very high for the southern sector of today’s severe risk, a strong cap is evident in CAM runs almost refusing outright to fire storms along the dryline. Despite explosive instability, this strong cap means the severe threat across this area is very uncertain.
Tomorrow (Western Corn Belt)
Despite an evident weakening of the trough feature, potent moisture influx is still expected from the southern Great Plains up through Iowa and Nebraska, exciting the severe storm potential again.
Uncertainty over severe potential remains over the possibility of morning convection, which may overspread Nebraska, Iowa and Missouri until the early afternoon. This could overall limit severe potential, especially further along the dryline which features dewpoints even higher than where cold air aloft is more present.
Because of these differences in lift vs. moisture, the real estate that storms have to work with may be quite narrow. Perhaps the most certain severe potential will be closer to the low pressure system, where an arc of mini-supercells capable of tornadoes will form somewhere near the NE/IA border, with >1,000 MLCAPE, >200 0-3km CAPE, very low LCL’s present. One caveat of this feature will be weak low-level shear, greatly limiting the significant tornado threat.
Saturday
Almost every single hallmark of a plains setup, to a caliber that hasn’t been seen in several years, is at play here.
A very powerful strongly diffluent 500mb longwave with upper 60s to near 70 degree dewpoints in the warm sector is evident in recent model runs.
Still, the major limiting factor that’s been seen especially on most global guidance is the lack of a stout EML to prevent early initiation.
Therefore, convective signals (especially off of the Euro) are very strong in southern Oklahoma into north Texas during the early afternoon, likely limiting convective potential into the evening hours. If this were to occur, it could be a saving grace from an even more potent plains setup with several violent tornadoes.
