• MESO: Severe potential MW

    From Weather Alert@454:1/105 to All on Fri Mar 25 16:05:00 2022
    ACUS11 KWNS 251918
    SWOMCD
    SPC MCD 251918
    INZ000-ILZ000-WIZ000-IAZ000-252145-

    Mesoscale Discussion 0337
    NWS Storm Prediction Center Norman OK
    0218 PM CDT Fri Mar 25 2022

    Areas affected...Parts of northeastern Iowa through southern
    Wisconsin and northern Illinois

    Concerning...Severe potential...Watch unlikely

    Valid 251918Z - 252145Z

    Probability of Watch Issuance...5 percent

    SUMMARY...Showers and isolated thunderstorms will overspread the
    region through late afternoon, some accompanied by a mix of frozen precipitation, strong wind gusts approaching severe limits, and
    occasional sharply reduced visibilities.

    DISCUSSION...An intensifying cyclonic, northwesterly jet streak is
    in the process of digging across and southeast of the Upper Midwest.
    This includes speeds within its core increasing in excess of 90 kt
    around 500 mb and 50 kt around 850 mb. Within the exit region of
    this jet streak, strong lower/mid tropospheric cooling is ongoing
    (including temps of -16 to -32C in the 700-500 mb layer),
    contributing to pronounced steepening of low-level lapse rates.
    This is currently becoming most prominent across parts of
    northeastern Iowa and southwestern Wisconsin into northern Illinois,
    aided by insolation, where deepening convective development is
    underway.

    Rapid Refresh forecast soundings suggest that the destabilizing
    thermodynamic profiles may become supportive of convection reaching
    15-20 thousand plus foot depths, and perhaps becoming capable of
    occasionally producing lightning. Given the cold nature of these
    profiles, including rather low freezing levels within a couple
    thousand feet above ground level, the well-mixed sub-cloud boundary
    layer probably will allow for a transition from rain to melting
    frozen precipitation ranging from graupel to snow in the stronger showers/downdrafts. This may also enhance the downward mixing of
    potentially damaging wind gusts to the surface, as activity develops southeastward through 22-00Z.

    ..Kerr.. 03/25/2022

    ATTN...WFO...LOT...MKX...DVN...ARX...

    LAT...LON 42019063 42979057 43268964 42408740 40558724 41118885
    41548989 42019063
    $$
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  • From Weather Alert@454:1/105 to All on Tue Mar 29 17:04:00 2022
    ACUS11 KWNS 292039
    SWOMCD
    SPC MCD 292038
    IAZ000-MOZ000-NEZ000-KSZ000-SDZ000-292245-

    Mesoscale Discussion 0339
    NWS Storm Prediction Center Norman OK
    0338 PM CDT Tue Mar 29 2022

    Areas affected...Mid-Missouri Valley

    Concerning...Severe potential...Watch possible

    Valid 292038Z - 292245Z

    Probability of Watch Issuance...60 percent

    SUMMARY...Elevated storms are expected to develop by late afternoon.
    These storms will pose a threat for large hail and isolated damaging
    winds. A watch is possible later this afternoon.

    DISCUSSION...Water vapor imagery shows a shortwave trough moving
    into western portions of Nebraska this afternoon. Signs of
    large-scale ascent are increasing in south-central Nebraska with
    cumulus deepening near the triple point. Observed soundings through
    the day from OAX show mid-level lapse rates in excess of 8 C/km
    along with an increasing warm nose around 800 mb. Despite very
    limited surface moisture return ahead of the surface low, continued
    elevated lift near the frontal zones is expected to promote storm
    development by late this afternoon. With the low-level jet expected
    to increase within the next 2-3 hours, some potential exists for
    isolated development to occur. These initial storms would be capable
    of small to marginally severe hail. Further mid-level cooling will
    occur by early evening, leading to an increase in storm
    coverage/intensity. Large hail will become a greater risk with time
    as elevated buoyancy increases.

    The threat for damaging winds will be limited by storms being rooted
    above the surface. However, an isolated damaging gust is possible.
    Wind gust potential will likely be maximized in northwest Missouri
    into southeast Nebraska where low-level moisture will be greater and
    storms may be nearly surface-based.

    Trends will continue to be monitored for a potential watch later
    this afternoon.

    ..Wendt/Hart.. 03/29/2022

    ATTN...WFO...DMX...EAX...FSD...OAX...TOP...GID...LBF...

    LAT...LON 40779474 40479483 40019539 39979636 40359735 41619809
    42009831 42549818 43099753 43309689 43259640 41649520
    41169491 40779474
    $$
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  • From Weather Alert@454:1/105 to All on Mon Apr 25 16:12:00 2022
    ACUS11 KWNS 251940
    SWOMCD
    SPC MCD 251939
    NYZ000-PAZ000-OHZ000-252145-

    Mesoscale Discussion 0563
    NWS Storm Prediction Center Norman OK
    0239 PM CDT Mon Apr 25 2022

    Areas affected...Parts of northeastern Ohio...northwestern Pennsylvania...western New York state

    Concerning...Severe potential...Watch unlikely

    Valid 251939Z - 252145Z

    Probability of Watch Issuance...20 percent

    SUMMARY...Thunderstorm activity may intense further while developing northeastward in a narrow corridor near/southeast of Lake Erie
    through 5-6 PM EDT. It still appears unlikely that a severe weather
    watch will be needed, but a couple of these storms may be
    accompanied by a few strong gusts approaching severe limits, and
    perhaps some potential for a brief tornado.

    DISCUSSION...A mid-level cyclonic vorticity center has been rapidly
    migrating north-northeastward at 50+ kt, and is now passing north of
    the Cleveland OH area. This has been accompanied by a sustained
    small, elongated cluster of convection, including more recent
    embedded thunderstorm development on its southern/southwestern
    periphery, which appears likely to spread along and southwest of the
    southern shores of Lake Erie into western New York state through
    21-22Z.

    Although, to this point, mixed-layer CAPE along this corridor
    remains weak (on the order of 250-500 J/kg), low-level lapse rates
    have become quite steep inland of the lake breeze in response to
    insolation and mixing. And Rapid Refresh output suggest that
    substantial modification of this environment could lead to
    increasing CAPE during the next few hours. This may become
    sufficient to support further thunderstorm development and
    intensification.

    The intersection of this activity with the lake breeze could provide
    a focus for a supercell structure or two with some risk for a
    tornado. Otherwise, locally strong surface gusts approaching severe
    limits appears the primary potential severe hazard, in the presence
    of deep-layer southwesterly ambient mean flow on the order of 40+
    kt.

    ..Kerr/Guyer.. 04/25/2022

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

    LAT...LON 43447836 43077721 41797848 41307941 40008217 40638202
    41678130 42227972 42687885 43447836

    $$
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  • From Weather Alert@454:1/105 to All on Thu Jun 23 17:21:00 2022
    ACUS11 KWNS 232057
    SWOMCD
    SPC MCD 232056
    MNZ000-WIZ000-SDZ000-NDZ000-232330-

    Mesoscale Discussion 1267
    NWS Storm Prediction Center Norman OK
    0356 PM CDT Thu Jun 23 2022

    Areas affected...Far northeast SD into central MN

    Concerning...Severe potential...Watch possible

    Valid 232056Z - 232330Z

    Probability of Watch Issuance...40 percent

    SUMMARY...The area is being monitored for possible severe storm
    development this afternoon and evening. While uncertain, a watch
    could eventually be needed for parts of northeast SD into central
    MN.

    DISCUSSION...Visible satellite imagery shows a modest uptick in
    boundary-layer cumulus along a weak surface trough extending across
    parts of central MN into northeast SD. While boundary-layer flow is
    veered south of the surface boundary, weak low-level warm advection
    is supporting a modest increase in low-level confluence. Earlier 12Z
    soundings over the northern Plains showed a plume of steep midlevel
    lapse rates which has now overspread parts of MN per RAP
    mesoanalysis. The steep midlevel lapse rates atop a
    moist/deeply-mixed boundary layer are contributing to
    moderate/strong surface-based buoyancy -- strongest over northeast
    SD into western MN where surface temperatures have climbed into the middle/upper 90s beneath the core of the steeper lapse rates.

    As diurnal destabilization continues amid the modest low-level
    confluence, isolated to widely scattered storm development may occur
    over parts of northeast SD into central MN this afternoon/evening.
    While deep-layer flow/shear is modest (25-35 kt of effective shear),
    the favorable buoyancy and at least some deep-layer shear could
    support isolated large hail initially. Eventually, damaging winds
    could become an increasing concern with any convective clustering
    amid the steep low/mid-level lapse rates. Overall confidence in
    storm development and maintenance is limited, though trends are
    being monitored and a watch could eventually be needed.

    ..Weinman/Grams.. 06/23/2022

    ATTN...WFO...DLH...MPX...FGF...ABR...

    LAT...LON 45909717 46649588 47299380 47309313 47029274 46489254
    45809276 45389329 44879655 45059710 45519732 45909717


    = = =
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