• MESO: Mesoscale Discussion 0832

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Thursday, May 19, 2022 21:54:31
    ACUS11 KWNS 192154
    SWOMCD
    SPC MCD 192154=20
    WIZ000-IAZ000-MNZ000-200000-

    Mesoscale Discussion 0832
    NWS Storm Prediction Center Norman OK
    0454 PM CDT Thu May 19 2022

    Areas affected...Far northern Iowa...southeast Minnesota...and
    western Wisconsin

    Concerning...Severe Thunderstorm Watch 246...

    Valid 192154Z - 200000Z

    The severe weather threat for Severe Thunderstorm Watch 246
    continues.

    SUMMARY...The potential for severe hail, and possibly sporadic wind
    damage, continues across parts of the upper Mississippi River
    valley. The threat will remain confined to far northern Iowa into
    southeast Minnesota for the next couple of hours, but may spread
    east through the late evening hours.

    DISCUSSION...Latest radar imagery from KMPX and KARX shows clusters
    of cells initiating along a warm frontal zone before quickly
    becoming displaced to the north of the boundary. Both recent RAP
    forecast soundings and mesoanalyses suggest this activity is
    elevated and rooted within the 850-700 mb layer. Several cells have
    shown signs of organized mid-level mesocyclones and numerous severe
    hail reports have been noted over the past 1-2 hours across MN into
    western WI. Latest MUCAPE estimates show the most favorable
    thermodynamic environment resides from south-central MN into
    southern WI, and cells have shown a weakening trend as they drift
    east into central WI. This trend is expected to largely continue
    over the next 1-2 hours due to the relatively slow northward
    progression of the warm frontal zone. A few cells may maintain
    intensity as they drift into the central WI, but the severe threat
    may not substantially increase until later this evening when a
    stronger mass response associated with an upstream upper-level
    trough shifts the warm frontal zone (and better instability)
    northward. Trends will continue to be monitored through the evening,
    and a watch is possible across parts of central WI as the severe
    potential increases.

    ..Moore.. 05/19/2022

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!7rAFr-EXDafj2KVm_KtWpk9sfjIWrIm9ETEB7K-zWB61J4SLcmIrn02fpmJsYd4OjSBHwVqCg= ezWxB4reV2rw9Rbhxc$ for graphic product...

    ATTN...WFO...GRB...MKX...DLH...ARX...MPX...DMX...

    LAT...LON 43819428 44539406 45169333 45419222 45499128 45479048
    45378982 45038936 44358912 43678926 43338975 43299080
    43299195 43319305 43379370 43819428=20


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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sunday, May 21, 2023 19:28:04
    ACUS11 KWNS 211927
    SWOMCD
    SPC MCD 211927=20
    IDZ000-WAZ000-212130-

    Mesoscale Discussion 0832
    NWS Storm Prediction Center Norman OK
    0227 PM CDT Sun May 21 2023

    Areas affected...Northeast WA into the ID Panhandle

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

    Valid 211927Z - 212130Z

    Probability of Watch Issuance...40 percent

    SUMMARY...Scattered thunderstorm development is expected later this
    afternoon, with a threat for isolated severe hail and wind gusts.
    The need for watch issuance is uncertain at this time.

    DISCUSSION...Relatively strong diurnal heating is underway early
    this afternoon across parts of eastern WA into northern ID. With dew
    points in the low/mid 50s F amid warming temperatures, MLCAPE has
    already increased into the 500-1000 J/kg range, and some further destabilization is possible through the afternoon. Weak high-based
    convection is ongoing across east-central WA, which may be
    associated with a low-amplitude shortwave trough moving
    northeastward in advance of a stronger mid/upper-level shortwave
    approaching the Pacific Northwest coast. This area of ascent
    combined with decreasing MLCINH is expected to result in stronger
    thunderstorm development later this afternoon, with an east-west
    oriented surface boundary across northeast WA expected to be a
    primary focus for initiation.=20=20

    Increasing midlevel flow will support sufficient vertical shear for
    organized convection, especially near/north of the surface boundary,
    where backed low-level flow will result in larger effective shear
    magnitudes. A couple of supercells may evolve with time, posing a
    threat of large hail and localized severe gusts. Storm coverage
    south of the surface boundary is more uncertain, due to weaker
    low-level convergence and a tendency for low-level moisture to mix
    out with time.=20

    With northeasterly storm motions expected across the area, storms
    developing along the surface boundary and moving through the most
    favorable environment may quickly move across the international
    border into British Columbia. Due to the potentially limited
    spatiotemporal extent of the threat, the need for watch issuance is
    uncertain at this time.

    ..Dean/Grams.. 05/21/2023

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!_hz0Ke7flRihHlkqEGrWOLdo_fvgwlwaGE_lc8nbYbJVZDxhLAmOJ4vQxfnq-GCKEiRVQAb9m= 6vmeS4qfxsKOhV1vC4$ for graphic product...

    ATTN...WFO...OTX...

    LAT...LON 47721784 48081938 49051953 49301878 49241744 49131655
    48311641 47821701 47721784=20


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