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SPC Mesoscale Discussions

Storm Prediction Center
SPC Mesoscale Discussions
  1. MD 1386 CONCERNING SEVERE THUNDERSTORM WATCH 437...438... FOR FAR SOUTHERN MINNESOTA INTO CENTRAL IOWA
    MD 1386 Image
    
    Mesoscale Discussion 1386
    NWS Storm Prediction Center Norman OK
    0509 PM CDT Tue Jul 05 2022
    
    Areas affected...far southern Minnesota into central Iowa
    
    Concerning...Severe Thunderstorm Watch 437...438...
    
    Valid 052209Z - 052315Z
    
    The severe weather threat for Severe Thunderstorm Watch 437, 438
    continues.
    
    SUMMARY...A derecho is expected to maintain some structure while
    traversing the MN/IA border for the next couple of hours, with
    severe winds still a concern. Damaging gusts, large hail, and a
    tornado also remain possible with storms preceding the derecho.
    
    DISCUSSION...A derecho-producing MCS, with a considerable history of
    producing significant severe winds, continues to progress along the
    IA/MN border. This MCS has a well-defined mesovortex along the
    northern periphery of a bow echo, where severe winds (some
    significant) continue to be reported. It is uncertain how long the
    MCS will maintain a classic bow-echo structure since the bow is
    beginning to interact with preceding storms. Though synoptic forcing
    remains quite weak, a corridor of extreme buoyancy resides ahead of
    the MCS, overspread by 35-40 kts of effective bulk shear, with the
    bulk shear vectors aligned roughly normal to the MCS bow. Current
    FSD radar shows very strong outbound velocity signatures with the
    bow, so damaging gusts (perhaps some significant) remain possible
    over the next 1-3 hours. Even if the derecho-MCS structure is
    disrupted by the preceding convection, the current CAPE/shear
    parameter space supports continued severe potential with any mature
    storms through the afternoon.
    
    ..Squitieri.. 07/05/2022
    
    ...Please see www.spc.noaa.gov for graphic product...
    
    ATTN...WFO...DVN...ARX...MPX...DMX...FSD...OAX...
    
    LAT...LON   42229674 42659609 43079558 43379540 43709519 43969457
                44049349 43879256 43399156 43159142 42849136 42489157
                42149201 41879274 41829410 41789498 41789584 42229674 
    
    
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  2. MD 1385 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF EASTERN MARYLAND INTO DELAWARE
    MD 1385 Image
    
    Mesoscale Discussion 1385
    NWS Storm Prediction Center Norman OK
    0450 PM CDT Tue Jul 05 2022
    
    Areas affected...portions of eastern Maryland into Delaware
    
    Concerning...Severe potential...Watch unlikely 
    
    Valid 052150Z - 052315Z
    
    Probability of Watch Issuance...20 percent
    
    SUMMARY...A damaging gust or brief tornado remains possible with the
    more persistent supercell structures over the next couple of hours.
    A WW issuance is unlikely given the isolated nature of the severe
    threat.
    
    DISCUSSION...Transient supercell structures have developed over the
    past hour across parts of the northern Mid Atlantic in association
    with a small but pronounced 500 mb vort max grazing the region. The
    21Z mesoanalysis depicts up to 1500 J/kg MLCAPE in place, driven
    primarily by rich, deep low-level moisture. Modest low to mid-level
    directional shear is contributing to sizable, curved hodographs (per
    2124Z DOX VWP), with mesoanalysis and RAP forecast soundings showing
    200-300 m2/s2 effective SRH. As such, a damaging gust or a brief
    tornado may accompany the more persistent supercell structures
    through the remainder of the afternoon. A WW issuance is not
    expected since the tornado threat is expected to remain sparse.
    
    ..Squitieri/Hart.. 07/05/2022
    
    ...Please see www.spc.noaa.gov for graphic product...
    
    ATTN...WFO...PHI...AKQ...LWX...
    
    LAT...LON   38867694 39327657 39477615 39437566 39197529 38847523
                38547532 38307554 38207596 38247645 38397683 38867694 
    
    
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  3. MD 1383 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF EXTREME EASTERN TENNESSEE...EXTREME SOUTHERN VIRGINIA...WESTERN INTO CENTRAL NORTH CAROLINA...FAR NORTHERN SOUTH CAROLINA
    MD 1383 Image
    
    Mesoscale Discussion 1383
    NWS Storm Prediction Center Norman OK
    0434 PM CDT Tue Jul 05 2022
    
    Areas affected...portions of extreme eastern Tennessee...extreme
    southern Virginia...western into central North Carolina...far
    northern South Carolina
    
    Concerning...Severe potential...Watch unlikely 
    
    Valid 052134Z - 052330Z
    
    Probability of Watch Issuance...20 percent
    
    SUMMARY...A couple of damaging gusts may accompany the stronger
    storm cores embedded within a southward moving squall line. The
    overall severe wind threat is expected to remain isolated through
    the remainder of the evening and a WW issuance is not expected.
    
    DISCUSSION...A modestly organized MCS has materialized over the past
    couple of hours across portions of the central Appalachians into the
    Carolina Piedmont, where a couple of damaging gusts have recently
    been reported. Deep-layer tropospheric flow/shear remain weak across
    much of the eastern U.S., with squall line organization driven
    predominantly by cold pool mergers in a moderately unstable
    environment. 2000-2500 J/kg MLCAPE resides ahead of the MCS/squall
    line, driven primarily by 8 C/km 0-3 km lapse rates. As such,
    adequate evaporative cooling within the boundary layer should
    support an isolated damaging gust threat through the remainder of
    the afternoon with the stronger storm cores.
    
    ..Squitieri.. 07/05/2022
    
    ...Please see www.spc.noaa.gov for graphic product...
    
    ATTN...WFO...AKQ...MHX...RAH...ILM...RNK...CAE...GSP...MRX...
    JKL...
    
    LAT...LON   35728351 36148385 36528413 36708412 36588338 36298234
                36008109 36117967 36477867 36817817 36777765 36657716
                36337709 35967722 35657759 35167847 34897909 34637973
                34378084 34258177 34248237 34438278 34888313 35728351 
    
    
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