• MESO: Mesoscale Discussion 1421

    From COD Weather Processor@1:2320/127 to wx-storm@lists.illinois.edu on Wed Jul 1 19:34:49 2026
    ACUS11 KWNS 011934
    SWOMCD
    SPC MCD 011934=20
    ILZ000-WIZ000-IAZ000-012130-

    Mesoscale Discussion 1421
    NWS Storm Prediction Center Norman OK
    0234 PM CDT Wed Jul 01 2026

    Areas affected...south-central ad eastern Iowa...northern
    Illinois...and southern Wisconsin.

    Concerning...Severe potential...Watch likely=20

    Valid 011934Z - 012130Z

    Probability of Watch Issuance...80 percent

    SUMMARY...The severe storm threat is expected to increase this
    afternoon and into the evening.

    DISCUSSION...A cluster of cumulus has had several initiation
    attempts with intermittent lightning across northeast Iowa. These
    initial attempts are likely struggling with the remaining
    mixed-layer inhibition observed by the 18Z DVN RAOB. Thus far, no
    storms have become rooted, but given the expansive nature of the
    cumulus cluster and repeated attempts in this region as well as
    additional boundary layer heating, expect eventual storm development
    from this activity. In addition, storms are likely across central
    and south-central Iowa this evening within the same maximum
    instability axis as ascent increases across this area. 50+ knots of
    mid-level flow (per DMX VWP) will support supercell storm mode and a
    threat for large hail and severe winds. As the low-level jet
    intensifies this evening, low-level shear will increase. Shear will
    be mostly unidirectional, but the strong speed shear, and any
    additional low-level vorticity along the boundary from earlier
    convection, could lead to some tornado threat this evening.=20

    A watch will likely be needed at some point this afternoon/evening.
    However, the timing remains somewhat uncertain. If the storm
    attempts across northeast Iowa become rooted, the watch may be
    issued soon, but if they continue to struggle, it may be later this
    afternoon before one is needed.

    ..Bentley/Guyer.. 07/01/2026

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!4uBcC76aHJI89tszC0GaScSZnrwpLCsR2572TI_XXn5QttuY61QoT7QyxCIWPwxIXt1waW_I7= Ux-teBfM7OLIQh-jyM$ for graphic product...

    ATTN...WFO...LOT...MKX...DVN...ARX...DMX...

    LAT...LON 40789292 40719462 41099473 41559435 42059358 43029144
    43588950 43598767 43208784 42778769 42258772 41528934
    40889169 40819262 40789292=20

    MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
    MOST PROBABLE PEAK WIND GUST...65-80 MPH
    MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN


    =3D =3D =3D
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    * Origin: Capitol City Weather Station (1:2320/127)