SPC Mesoscale Discussions
Storm Prediction Center

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SPC MD 1386
MD 1386 CONCERNING SEVERE THUNDERSTORM WATCH 437...438... FOR FAR SOUTHERN MINNESOTA INTO CENTRAL IOWAMesoscale 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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SPC MD 1385
MD 1385 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF EASTERN MARYLAND INTO DELAWAREMesoscale 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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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 CAROLINAMesoscale 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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