A low risk of severe thunderstorms will exist this afternoon and early evening from Nebraska to Oklahoma. A powerful storm system will move east out onto the Plains with tons of associated lift. Storms should form from north to south through the afternoon.

    Locations:

    • Southwestern and southern Nebraska
    • Central and eastern Kansas
    • Eastern Oklahoma

    Threats:

    • Large hail (1 to 1.5 inches possible)
    • Damaging wind gusts (60-80 mph possible)
    • Very low to low tornado risk. Relatively highest early near the low in Nebraska/North Kansas and then a very low risk in Eastern Oklahoma in the early evening.

    Timing

    • This afternoon through early evening

    Discussion

    • Weather Development: A powerful upper-level disturbance is pushing into the Central Great Plains, accompanied by a deepening surface low.
    • Northern Storm Type: Expect initial development of a few potentially supercellular storms, before transitioning into a more linear storm mode in the north.
    • Southern Storm Type: Further south, as a pacific front and dryline consolidate and move east, storms should form in the late afternoon. These will be a mix of multicells and supercells.
    • Limitations:
      • Limited moisture (low dewpoints) will restrict the overall intensity and coverage of severe weather in the north.
      • Moisture is also not excellent to the south, but 60 dewpoints will be nosing north in the early evening in Southern Oklahoma.
      • Instability will be weak, further reducing potential storm strength.

    Technical Discussion

    Aloft, a jet streak will emerge out onto the Plains with a core of nearly 100kts.
    A strong low-level jet will establish this evening over Eastern Oklahoma and Kansas. With the winds at 850 being over 60kts in Kansas and approaching 40kts in Eastern Oklahoma.
    Ample low-level instability will exist in an axis from SW to NE of about 100 miles along the dryline. This will give most storms 120 minutes or so of useable instability before they run into less unstable air to the east.
    The HRRR fires storms along the dryline by mid-late afternoon. I’m expecting storm initiation to begin by 3 p.m. near the low and we should have storms to the Red River no later than 6 p.m.
    Storms will also line out from north to south, with the cells further south likely being isolated for much longer. Given the increasing moisture and strong low-level flow, I actually think there’s a non-zero tornado risk as far as the Red River Valley today. Damaging winds will be the primary threat with hail a secondary threat. However it is important to note that as long as supercells exist in any target, there will be a tornado threat.
    Given that we’re almost certainly chasing Oklahoma today, a glance at soundings in the evening shows nearly 1000 j/kg of MLCAPE along with deep moisture and strong shear. Effective SRH values of over 200 m2/s2 will be favorable for storm rotation. A tornado or two are possible if a dominant supercell can root in this environment. But only if.