Severe thunderstorms capable of tornadoes, large to very large hail, and severe gusts are possible across parts of the Dakotas and Minnesota.
NOTE – A risk for tornadoes may also develop across the central Gulf Coast region in association with the landfall of Tropical Storm Cristobal.
Preceding the northern Rockies/Great Basin-centered upper trough, a belt of strong southwesterly mid/high-level winds will overspread the north-central High Plains and Dakotas to northern Minnesota through tonight. Southerly low-level winds will contribute to moisture streaming northward through the eastern Dakotas during the day.
Strong heating and the increasingly rich low-level moisture will yield a moderate to very unstable air mass, particularly across central/northeast South Dakota into eastern North Dakota and northwest Minnesota. In this corridor, upwards of 3000-4000 J/kg MLCAPE is expected in association with surface dewpoints in the middle/upper 60s to around 70 F.
The most intense surface-based development is expected by mid/late afternoon near/northeast of a weak surface wave and near/just east of a southward-extending trough across central South Dakota, and north-northeastward across eastern North Dakota/far northwest Minnesota toward the warm frontal vicinity.
Given the degree of instability and long hodographs with robust 50+ kt effective shear, intense supercells capable of very large hail are initially expected within this corridor.
Other storms developing near/behind the front across the Black Hills vicinity and northeast Wyoming/southeast Montana toward west-central North Dakota will also pose a severe risk as they quickly spread northeastward late this afternoon and evening.
Large hail aside, several tornadoes are possible, including the possibility for a STRONG tornado or two. Such a strong tornado threat would be heightened pending a maintenance of some semi-discrete supercells through the early evening (roughly 00Z-03Z time frame).
This is when low-level jet aided shear/SRH is expected to appreciably strengthen across north-central/northeast South Dakota into eastern North Dakota/northwest Minnesota.
A mixed convective mode should otherwise evolve during the evening with increasingly prevalent northeastward-spreading clusters/bowing segments, with damaging wind potential also increasing.
Tornado Probabilities – Dakotas and Minnesota
Tornado Probabilities – Louisiana and Mississippi – Florida
The left exit region of a powerful cyclonically curved upper jet will overspread the eastern Great Basin/central Rockies today. Steep low-level lapse rates and strong mid-level flow will support strong to severe thunderstorm development by peak heating near/ahead of an eastward-moving cold front.
The potential will exist for thunderstorm-related severe-caliber wind gusts this afternoon/early evening, particularly across northeast Utah/northwest Colorado into Wyoming. That said, the severe risk is not expected to be quite as intense or widespread as yesterday.
…Gulf Coast from Louisiana to northern Florida...
As Cristobal approaches the southeast Louisiana this afternoon, low/mid-level winds are forecast to gradually intensify particularly across southeast Louisiana and southern Mississippi/Alabama and western Florida Panhandle. Diurnal destabilization will contribute to a risk for shallow rotating storms and a couple of tornadoes are possible across region.
Farther to the east, across the northern Florida Peninsula, low-level winds/shear are expected to be weaker, but potentially sufficient for a few organized/rotating storms through the afternoon. A tornado and/or thunderstorm-related wind damage could occur. SPC/Storm Prediction Center: Guyer/Leitman.. 06/07/2020
Are you prepared?
Now will be a good time to check your weather radios and have several ways to receive watches & warnings