• MESO: Mesoscale Discussion 1641

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tuesday, November 13, 2018 06:16:54
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    ACUS11 KWNS 130516
    SWOMCD
    SPC MCD 130516
    NCZ000-SCZ000-130745-

    Mesoscale Discussion 1641
    NWS Storm Prediction Center Norman OK
    1116 PM CST Mon Nov 12 2018

    Areas affected...Portions of coastal NC/SC

    Concerning...Severe potential...Watch possible

    Valid 130516Z - 130745Z

    Probability of Watch Issuance...60 percent

    SUMMARY...Thunderstorms will move northeastward across parts of the
    coastal Carolinas overnight, with both an isolated tornado and
    strong to locally damaging wind threat. Watch issuance is possible.

    DISCUSSION...A strong southerly low-level jet (around 40-50 kt) has
    developed over the eastern Carolinas per recent VWPs from KLTX and
    KMHX. Warm air advection attendant to the LLJ has encouraged recent thunderstorm development along a surface front very near the coast
    of SC as of 05Z. A weak surface low is expected to develop
    northeastward along this boundary overnight, and continued warming
    and moistening of the low levels will likely occur across coastal
    NC/SC. Forecast soundings from latest RAP/HRRR guidance indicate
    there will be some threat for surface-based thunderstorms where
    dewpoints can reach into the upper 60s to around 70. Strong speed
    shear mainly in the 0-1 km layer will contribute to large effective
    SRH values across this region, potentially in excess of 300 m2/s2.
    Even though instability will remain weak owing to poor lapse rates
    through the column, MLCAPE up to 1000 J/kg will likely be sufficient
    for surface-based thunderstorms along/near the coast. Effective bulk
    shear values of 45-55 kt will support supercells, and the strong
    low-level shear suggests isolated tornadoes may occur with these
    storms. Strong to damaging straight-line winds will also be a
    possibility with any cluster that may evolve. Short-term guidance
    suggests an appreciable inland severe threat may develop near the
    coastal NC/SC border region by about 07Z, and a watch may eventually
    be needed.

    ..Gleason/Thompson.. 11/13/2018

    ...Please see www.spc.noaa.gov for graphic product...

    ATTN...WFO...MHX...ILM...

    LAT...LON 33287880 33677920 33897923 34257874 34557823 35837665
    36047602 36067562 35667542 35207548 34997608 34547650
    33907789 33287880



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