SPC Mesoscale Discussions

1. SPC MD 1386

   MD 1386 CONCERNING SEVERE THUNDERSTORM WATCH 437...438... FOR FAR SOUTHERN MINNESOTA INTO CENTRAL IOWA
   

   
   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. SPC MD 1385

   MD 1385 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF EASTERN MARYLAND INTO DELAWARE
   

   
   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. SPC MD 1383

   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
   

   
   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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