• MESO: Mesoscale Discussion 1966

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sun Nov 20 01:25:52 2022
    ACUS11 KWNS 200125
    SWOMCD
    SPC MCD 200125=20
    NYZ000-PAZ000-OHZ000-200730-

    Mesoscale Discussion 1966
    NWS Storm Prediction Center Norman OK
    0725 PM CST Sat Nov 19 2022

    Areas affected...Portions of far western New York into extreme
    northwest Pennsylvania and extreme northeast Ohio

    Concerning...Heavy snow=20

    Valid 200125Z - 200730Z

    SUMMARY...A heavy snow band should move off of lake Erie in the next
    couple of hours, supporting 2-3 inch/hr snowfall rates for areas
    east of the shoreline. Near-zero visibility is possible at times,
    with travel conditions also expected to become dangerous.

    DISCUSSION...An upper trough and associated surface lee trough/cold
    front is moving eastward across the Great Lakes/Ontario region and
    should progress across Lake Erie soon. Convergence along the cold
    front is already supporting intensification of a pre-existing band
    of snow over Lake Erie, and this band should shunt eastward with the
    passage of the cold front. As this occurs, strong low-level
    convergence and subsequent rapid uplift of a low-level buoyant
    airmass, characterized by 8-9 C/km low-level lapse rates (per last
    few mesoanalysis runs), will support an appreciable fetch of
    moisture before and during the time the snow band moves ashore.=20

    2-3 inch/hr snowfall rates are likely in association with the band.
    While the band may not progress as rapidly inland as a snow squall,
    rapid decreases in visibility along with gusty winds are likely,
    promoting dangerous travel conditions. High-resolution deterministic
    and ensemble guidance also suggests heavy snow moving ashore around
    02-03Z (9-10 PM EST) and peaking around 06Z (after midnight EST).

    ..Squitieri.. 11/20/2022

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!8QlVvFZaeb90OGvth00yGWHhB062A4zwhb7RxzyKu_wj6mq6kXNkOjkEfFZXFgV1P5XNBYT_U= sv1TWuWzvFj07OBBIU$ for graphic product...

    ATTN...WFO...BUF...CTP...PBZ...CLE...

    LAT...LON 43217892 43337852 43357815 43287787 43117775 42807766
    42307792 41867838 41467923 41278029 41278099 41398142
    41578146 41758119 42008049 42297977 42597920 42777898
    42977900 43087896 43217892=20


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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sat Aug 12 17:57:40 2023
    ACUS11 KWNS 121757
    SWOMCD
    SPC MCD 121757=20
    TNZ000-NCZ000-KYZ000-GAZ000-ALZ000-122000-

    Mesoscale Discussion 1966
    NWS Storm Prediction Center Norman OK
    1257 PM CDT Sat Aug 12 2023

    Areas affected...portions of middle and eastern TN...northern
    AL...northwestern GA...and far western NC

    Concerning...Severe Thunderstorm Watch 633...

    Valid 121757Z - 122000Z

    The severe weather threat for Severe Thunderstorm Watch 633
    continues.

    SUMMARY...Threat for damaging wind gusts increasing this afternoon
    across WW 633. An additional Severe Thunderstorm Watch is possible
    downstream and east of WW 633.

    DISCUSSION...An organized QLCS is currently moving through WW 633
    with a history of damaging wind reports. Cold pool deficits appear
    to be around 10 degrees F based on observations at and around KBNA.
    KOHX and TBNA radar observations also show multiple mesovortices
    along the leading edge of the system's cold pool, particularly along
    the eastern edge to the left of the system's apex.

    Damaging wind gusts (40-55 kts) are expected to continue in WW 633
    in association with this system. Current surface observations and
    short-term RAP forecast profiles depict an uncapped boundary layer
    and over 3000 J/kg of MLCAPE. Lower-layer lapse rates are not very
    steep (around 6 C/km), but a residual elevated mixed layer aloft
    (around and above 700 mb) will foster ample buoyant vertical
    accelerations atop forced ascent along the outflow. RAP and NAM
    profiles in the system's inflow depict modest veering shear in low
    levels (around 15-20 kts from 0-1 km AGL) with west-northwesterly
    flow around 40-50 kts aloft. When accounting for observed mesovortex
    motion, much of the low-level shear is crosswise, at least prior to
    potential mesoscale modification just ahead of the QLCS.
    Interactions between the cold pool and local environment --
    especially in the vicinity of a rear-inflow jet currently centered
    near DeKalb County -- will continue to favor damaging-wind
    production across WW 633. Multiple mesovortices will provide local
    enhancements to the broader damaging-wind field, particularly along
    and to the north of the bow apex in Middle TN. Convective trends
    will continue to be monitored for possible downstream watch issuance
    later this afternoon.

    ..Flournoy.. 08/12/2023

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!8IvrirOi7Qm2hQcJX14bikhtK7mebtaHGU5m-iD9NGjwGLuzafMRDNB2WTV8fLaewQbT1kTpL= l7BBPp2cD5Qx7WKXsU$ for graphic product...

    ATTN...WFO...GSP...MRX...JKL...FFC...OHX...BMX...HUN...

    LAT...LON 34358750 34868762 35228726 35418677 35708641 35988619
    36208612 36438615 36618588 36598486 36588338 35938325
    35128353 34548415 34178499 34018587 34038660 34358750=20


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