MD 0435 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR PORTIONS OF EASTERN OKLAHOMA…WESTERN ARKANSAS…AND FAR NORTHEASTERN TEXAS
Mesoscale Discussion 0435 NWS Storm Prediction Center Norman OK 1121 AM CDT Wed May 16 2018 Areas affected...Portions of eastern Oklahoma...western Arkansas...and far northeastern Texas Concerning...Severe potential...Watch unlikely Valid 161621Z - 161845Z Probability of Watch Issuance...20 percent SUMMARY...Two MCVs over central and eastern Oklahoma are expected to contribute to scattered thunderstorm development over the next few hours. Severe wind gusts and marginally severe hail are the primary threats. A Severe Thunderstorm Watch is not anticipated at this time, but conditions will be monitored closely. DISCUSSION...Overnight convection has once again produced MCVs over the area, partially as an enhancement of a subtle mid-level perturbation moving over the top of the building ridge. The 12z OUN raob sampled the enhancement in mid-level flow associated with these MCVs with wind speeds > 40 kt in the 650-500 mb layer and a peak wind of 55 kt at 565 mb. Moderate sub-tropical flow in upper levels, perhaps enhanced by a separate area of convection over the Texas panhandle, also is impinging on the area and is producing moderate diffluence aloft. Southeast and east of the MCVs, strong heating is occurring on either side of a dying stationary front amidst surface dewpoints in the upper 60s to low 70s. The above factors suggest thunderstorms will increase no later than early afternoon over the area, which is supported by recent HRRR guidance. While the background wind/vertical shear would suggest weakly organized thunderstorm clusters, the enhancement in vertical shear and mesoscale lift provided by the MCVs is expected to produce some convective organization in the form of a small MCS with perhaps some transient bowing clusters. Despite some convective overturning in previous days, moderate mid-level lapse rates remain over the area, and boundary-layer moisture is sufficient to support moderate instability --1500-2000 J/kg of MLCAPE by early afternoon. The primary threat will be severe wind gusts with any of the storms, particularly those that develop more persistent rotation. A marginally severe hail threat will also accompany the cells that show some rotation. While the extent of the severe coverage is not expected to warrant a Severe Thunderstorm Watch at this time, trends in both storm coverage and intensity will be monitored closely. ..Coniglio/Weiss.. 05/16/2018 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LZK...SHV...TSA...FWD...OUN... LAT...LON 36239526 36439439 36399322 36149238 36029225 35599205 34579198 34049219 33589254 33159319 33049402 33169465 33509525 34119568 34529586 34819591 35239589 35399584 35949564 36239526
from SPC Mesoscale Discussions http://bit.ly/2rN3s54
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