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Mesoscale Discussion 648 | |
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Mesoscale Discussion 0648 NWS Storm Prediction Center Norman OK 1107 AM CDT Mon May 06 2024 Areas affected...Far northwest Nebraska into western South Dakota and far southwest North Dakota Concerning...Severe potential...Watch possible Valid 061607Z - 061800Z Probability of Watch Issuance...40 percent SUMMARY...Thunderstorms developing along a cold front in the vicinity of a deepening surface low are expected to continue intensifying through the mid-afternoon hours. This activity may strengthen to severe limits and require watch issuance by late morning/early afternoon. DISCUSSION...Over the past hour, strong surface pressure falls (on the order of 1-2 mb/hour) have been observed across the western Dakotas amid increasing synoptic ascent over the northern High Plains. Concurrently, a Pacific cold front is pushing east and impinging on a narrow corridor of returning moisture. Consequently, weak convection has developed along the front and in the vicinity of the surface low. The expectation for the next several hours is for this activity to intensify owing to a combination of continued theta-e advection into a narrow warm sector (confined to the east by thick low/mid-level stratus that is resulting in muted diurnal warming) and steepening mid-level lapse rates associated with strong synoptic ascent and cooling temperatures aloft. MLCAPE values are forecast to reach 1500-2000 J/kg by mid-afternoon, which appears to be on track based on recent observed trends. Southerly mid/upper-level winds will support off-boundary organization of cells that may favor discrete to semi-discrete storm modes. Large hail (most likely 1.0 to 1.5 inches in diameter) and severe gusts will be the predominant hazard, but low-level helicity within the warm sector (observed values around 150 m2/s2 are noted in the KUDX VWP) combined with ample ambient vorticity along the boundary should support a tornado threat with more intense cells. The narrow spatial extent of the warm sector introduces some uncertainty into the overall coverage of the severe threat, but trends will continue to be monitored for the need of watch issuance. ..Moore/Smith.. 05/06/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ABR...BIS...LBF...UNR...CYS...BYZ... LAT...LON 42820272 43630338 43870382 44260430 44580466 45050498 45570517 46000490 46370422 46430302 46240166 46030122 45370069 44520052 43800051 42790060 42310085 42020150 42200213 42820272 |
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