• MESO: Mesoscale Discussion 0854

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sat Jun 5 18:34:18 2021
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    ACUS11 KWNS 051834
    SPC MCD 051833=20

    Mesoscale Discussion 0854
    NWS Storm Prediction Center Norman OK
    0133 PM CDT Sat Jun 05 2021

    Areas affected...Portions of Northern New England

    Concerning...Severe potential...Watch possible=20

    Valid 051833Z - 052030Z

    Probability of Watch Issuance...40 percent

    SUMMARY...There is uncertainty in convective evolution in northern
    New England. A WW is possible this afternoon, but timing is still
    uncertain. Observational trends will continue to be monitored.

    DISCUSSION...There remains a fair amount of uncertainty as to the
    exact evolution of convection this afternoon across northern New
    England. 12Z CAM guidance presents a wide array of possible
    outcomes. Trends in surface observations and visible satellite
    depict at least two plausible scenarios. First, a band of elevated
    convection near Burlington, VT, continues to move southeastward
    producing little to no lightning. This features, in some guidance,
    is forecast to intensify as it encounters greater instability to the
    southeast near the southern Maine and New Hampshire. In those
    locations, temperatures have already risen to near 90 F with
    dewpoints currently holding in the upper 50s to low 60s F. Another
    area of potential development is likely in northern New Hampshire
    into adjacent portions of Maine along a differential heating
    boundary. There, cumulus have continued to deepen of the last hour
    and that trend should continue. Given the steep low-level lapse
    rates and moderate flow off the surface, strong/damaging wind gusts
    are the primary threat with storms this afternoon. Objectively
    analyzed 40-50 kts of effective shear will promote organized storms,
    some perhaps supercellular. Discrete storms would be capable of
    marginally severe hail and perhaps a tornado. A WW is possible this
    afternoon, though timing is uncertain. Observational trends would
    suggest development in perhaps 2-3 hours. These trends will continue
    to be monitored.

    For portions of northern Maine, uncertainty is higher given
    remaining cloud cover and cooler temperatures. The most probable
    scenario in this region is that storms will initiate somewhere in
    the St. Lawrence River vicinity and move southeastward into the
    region. This activity would more likely occur later this afternoon
    given the inhibition that is yet to be overcome.

    ..Wendt/Guyer.. 06/05/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!qXaEL4chWybhOPOr2OP3Q3GILhIWSl4i1W4KtoRtcSMqTXI9F6QDOKdVcz9e9Qaz78DGXkbV$=
    for graphic product...


    LAT...LON 44147415 44697256 45066974 45146881 44686841 44096931
    43687017 43447051 43367120 44147415=20

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