• MESO: Mesoscale Discussion 1696

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Mon Sep 6 11:35:03 2021
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    ACUS11 KWNS 061134
    SPC MCD 061134=20

    Mesoscale Discussion 1696
    NWS Storm Prediction Center Norman OK
    0634 AM CDT Mon Sep 06 2021

    Areas affected...portions of western/northern NY -- near Lake
    Ontario and eastward to the Adirondacks.

    Concerning...Severe potential...Watch unlikely=20

    Valid 061134Z - 061400Z

    Probability of Watch Issuance...20 percent

    SUMMARY...Fast-moving thunderstorms may produce strong/locally
    damaging wind, with a gust or two near severe/50-kt levels and
    waterspouts possible, as they move along Lake Ontario. Strong gusts
    also may occur on adjoining shorelines and eastward over parts of
    northern NY through at least 15Z. The severe potential appears
    isolated and marginal enough that a watch is not expected at this

    DISCUSSION...Satellite and radar imagery indicate an increasingly
    organized band of thunderstorms over western/central Lake Ontario as
    of 1130Z, moving eastward about 45 kt. The convective band may
    lengthen (especially northward) with time as well, into parts of
    northern NY downshear from the lake.=20=20

    Cooling aloft -- superimposed on a relatively warm and moist
    boundary layer located over Lake Ontario -- will support this
    activity as it crosses the remainder of the lake during the next
    couple hours. Thereafter, pockets of early diurnal heating behind a
    previous cloud/precip area may yield enough boundary-layer
    destabilization to weaken MLCINH and enable surface-based buoyancy
    eastward toward the Adirondacks, sustaining the convective/marginal
    severe threat. Modified forecast soundings suggest steepening
    low/middle-level lapse rates over the lake, and surface dew points
    in the mid 50s to near 60 F, foster MLCAPE in the 300-800 J/kg

    Nearly unidirectional flow with height is evident from just above
    the surface through the convective column, limiting bulk shear,
    despite strong mid/upper flow. Effective-shear magnitudes should
    remain only in the 25-35-kt range over most of the area. Still, the fast-moving (40-45-kt) nature of the convection suggests enough
    momentum transfer may occur to yield gusts approaching severe limits
    and capable of minor damage with this activity. The steep lapse
    rates also may enable enough stretching of leading-edge
    boundary-layer vorticity for waterspouts.

    ..Edwards.. 09/06/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!tyTFIFm13wo7efgRcKTsgCgZdaAICVGqnSUYdsbCnxsjkHGDIUiJ6YP_afA3Dzlr9QkgBwD1$=
    for graphic product...


    LAT...LON 44977423 44547399 43997368 43337405 43177477 43117610
    43287823 43477813 43627799 43607685 44137645 44377585
    44467581 44757537 45007489 44977423=20

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