• Severe threat continues NE/KS/IA/MN

    From Mike Powell@618:250/6 to All on Mon May 18 00:00:38 2026
    There has been a Tornado Emergency in this watch!

    MOST PROBABLE PEAK TORNADO INTENSITY...120-145 MPH
    MOST PROBABLE PEAK WIND GUST...65-80 MPH
    MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN

    ACUS11 KWNS 172214
    SWOMCD
    SPC MCD 172213
    NEZ000-KSZ000-172315-

    Mesoscale Discussion 0757
    NWS Storm Prediction Center Norman OK
    0513 PM CDT Sun May 17 2026

    Areas affected...portions of central and eastern Nebraska into
    northern Kansas

    Concerning...Tornado Watch 214...

    Valid 172213Z - 172315Z

    The severe weather threat for Tornado Watch 214 continues.

    SUMMARY...The severe threat will continue to increase through the
    evening hours. 2+ inch diameter hail, 75+ mph wind gusts, and
    tornadoes are all possible with mature, sustained supercells. Swaths
    of severe wind may become the predominant concern if storm mergers
    occur and storms get undercut by the cold front.

    DISCUSSION...Supercells are maturing across central/eastern
    Nebraska, ahead of the merging cold front/dryline. These storms are
    rapidly maturing in an environment characterized by 3500+ J/kg
    MLCAPE and 40+ kts of effective bulk shear, which is more than
    adequate for intense supercells. Current live streams depict a
    strong tornado in progress over Howard County, NE, or roughly 15
    miles north of Grand Island.

    Low-level shear, while currently modest will increase markedly ahead
    of the ongoing storms, which will support larger, curved hodographs.
    As such, supercells that mature and sustain themselves will have the
    potential to produce 2+ inch diameter hail and tornadoes, with
    additional strong tornadoes possible. However, the ongoing storms in
    Nebraska may become undercut by the cold front soon, which could
    also counter future strong tornado potential with those particular
    storms. Therefore, mesocyclonic tornado potential is strongly
    conditional on supercells remaining discrete ahead of the cold front.

    High-resolution deterministic and ensemble guidance strongly
    suggests that storms across eastern NE into northern KS will merge
    into one or more bowing segments. Should this occur, 75+ mph winds
    and EF0-EF2 QLCS tornadoes will become the main concerns.

    ..Squitieri.. 05/17/2026

    ATTN...WFO...OAX...TOP...ICT...GID...

    MOST PROBABLE PEAK TORNADO INTENSITY...120-145 MPH
    MOST PROBABLE PEAK WIND GUST...65-80 MPH
    MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN

    ***

    MOST PROBABLE PEAK TORNADO INTENSITY...100-125 MPH
    MOST PROBABLE PEAK WIND GUST...65-80 MPH
    MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN

    ACUS11 KWNS 172246
    SWOMCD
    SPC MCD 172245
    MNZ000-IAZ000-172345-

    Mesoscale Discussion 0760
    NWS Storm Prediction Center Norman OK
    0545 PM CDT Sun May 17 2026

    Areas affected...portions of northern Iowa into southern Minnesota

    Concerning...Severe potential...Tornado Watch likely

    Valid 172245Z - 172345Z

    Probability of Watch Issuance...80 percent

    SUMMARY...The severe threat will increase over the next few hours.
    Severe wind and hail are likely, with tornadoes also possible. A
    Tornado Watch may be needed soon to address the impending threat.

    DISCUSSION...A bowing QLCS is traversing the far western IA/MN
    border, with a recent history of marginal severe hail/wind occurring
    with an embedded supercell structure. This QLCS is tracking eastward
    toward the axis of a 30-40 kt low-level jet, where low-level shear
    is increasing (i.e. 200+ m2/s2 effective SRH per 22Z mesoanalysis). Furthermore, 8+ C/km mid-level lapse rates are overspreading upper
    60s to near 70 F surface dewpoints in the warm sector ahead of the
    QLCS, yielding up to 3000 J/kg MLCAPE. With 40+ kts of effective
    bulk shear also in place, potential exists for the QLCS to
    strengthen, with a corresponding increase in severe wind and hail
    potential. Line-embedded tornadoes may also occur, especially with
    portions of the QLCS that interact with an approaching warm front. A
    Tornado Watch may need to be issued in the next couple of hours.

    ..Squitieri/Smith.. 05/17/2026

    ATTN...WFO...ARX...MPX...DMX...FSD...

    MOST PROBABLE PEAK TORNADO INTENSITY...100-125 MPH
    MOST PROBABLE PEAK WIND GUST...65-80 MPH
    MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN

    $$


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