MD 1721 CONCERNING SEVERE POTENTIAL…WATCH LIKELY FOR EASTERN KANSAS…FAR SOUTHEAST NEBRASKA…FAR SOUTHWEST IOWA AND NORTHWEST MISSOURI
Mesoscale Discussion 1721 NWS Storm Prediction Center Norman OK 0123 PM CDT Sat Oct 21 2017 Areas affected...eastern Kansas...far southeast Nebraska...far southwest Iowa and northwest Missouri Concerning...Severe potential...Watch likely Valid 211823Z - 212100Z Probability of Watch Issuance...95 percent SUMMARY...Thunderstorms are expected to develop along the east-southeastward progressing cold front across eastern Kansas later this afternoon. Once initiation occurs, storms will quickly intensify with damaging wind gusts, hail and a tornado or two possible into the evening hours. A watch will likely be needed by 20-21z. DISCUSSION...Breaks in low level clouds have allowed temperatures to warm into the mid to upper 70s across much of eastern KS early this afternoon. With dewpoints in the low and mid 60s, MLCAPE values have increased to 1500-2000 J/kg. The VAD wind profile from the DDC radar also has shown a slight increase in midlevel winds over the last 30 minutes or so, suggesting the shortwave impulse over northeast NM is beginning to eject east/northeast into the Plains. Furthermore, cumulus along the front from far northwest OK into central/eastern KS and southeast NE is becoming increasingly congested with some vertical growth evident. In conjunction with hi-res HRRR guidance, this suggests convective initiation should occur within the next couple of hours. Steep midlevel lapse rates and effective shear in excess of 35 kt will aid in storms quickly becoming severe with at least a brief window of opportunity for semi-discrete cells. However, the quickly progressing cold front and front-parallel deep-shear vectors will result in rather fast upscale growth. Any cells that can stay semi-discrete will pose a threat for large hail and damaging wind. Once upscale growth occurs, a transition to mainly a damaging wind threat is expected. While forecast low-level hodographs are unimpressive, they are adequate for low-end tornado potential and a tornado or two can not be ruled out either in an isolated cell or within embedded mesovorticies along the leading edge of the squall line. A watch will likely be needed between 20-21z. ..Leitman/Thompson.. 10/21/2017 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...SGF...DMX...EAX...OAX...TOP...ICT... LAT...LON 37799510 37369554 37069617 37049691 37009757 37059809 37249826 37629815 37879805 38379762 39069719 39599690 40569669 41019645 41289596 41299538 41179467 40929423 40579408 40009408 38909433 38309470 37799510
from SPC Mesoscale Discussions http://bit.ly/2gtByFW
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