MD 1397 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR PORTIONS OF NORTHERN KANSAS INTO NORTHWEST MISSOURI
Mesoscale Discussion 1397 NWS Storm Prediction Center Norman OK 0313 PM CDT Sat Jul 22 2017 Areas affected...Portions of northern Kansas into northwest Missouri Concerning...Severe potential...Watch unlikely Valid 222013Z - 222245Z Probability of Watch Issuance...20 percent SUMMARY...Isolated severe thunderstorm development may occur around the 21Z-22Z time frame in parts of northern Kansas, with activity developing eastward -- toward and across the lower Missouri Valley vicinity -- into the evening. Present indications are that Watch issuance is unlikely. DISCUSSION...Baroclinic circulations along a west-east frontal zone -- stretching from southwest of the Hill City KS area to north of Topeka KS to south of Kirksville MO -- are being amplified in the vicinity of north-central KS. This is in response to the strongest surface heating and resultant diurnally enhanced boundary-layer circulations, while a precipitation-reinforced boundary is enhancing mesoscale convergence between Hill City and Colby KS. A band of boundary-layer cumulus congestus is already become agitated within an arc from this focused zone of stronger convergence into north-central KS. Continued erosion of antecedent capping owing to surface temperatures nearing/breaching 100F may permit thunderstorm formation within a couple of hours, with subsequent convective development occurring eastward toward the Kansas River Valley vicinity into the late afternoon, with activity spreading/developing into the lower Missouri Valley vicinity into the evening hours. Steep tropospheric lapse rates supporting a strongly buoyant air mass on either side of the front should support vigorous updrafts. Isolated severe hail could occur -- especially during incipient updraft phases. However, effective shear around 20-25 kt suggests limited potential for sustained, rotating updrafts -- limiting severe-hail coverage and magnitude. Sizable surface dewpoint depressions -- on the order of 20-25F -- suggest that evaporative cooling will enhance strong convective downdrafts aided by DCAPE of 1700-2000 J/kg. Strong convective outflow could produce isolated severe wind gusts, especially if smaller-scale convective clustering/upscale growth were to develop eastward toward the lower Missouri Valley region into the evening hours. However, the lack of stronger vertical shear and forcing for ascent cast considerable doubt on prospects for a larger/more organized convective system to evolve. ..Cohen/Grams.. 07/22/2017 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...EAX...TOP...ICT...GID...DDC...GLD... LAT...LON 39530007 39759859 39839483 39739290 38799352 38659929 39020027 39530007
from SPC Mesoscale Discussions http://bit.ly/2uKNSKQ
Be First to Comment