MD 1692 CONCERNING SEVERE POTENTIAL…WATCH POSSIBLE FOR PORTIONS OF SOUTHEAST NEBRASKA…SOUTHWEST IOWA…AND FAR NORTH CENTRAL KANSAS
Mesoscale Discussion 1692 NWS Storm Prediction Center Norman OK 0314 PM CDT Fri Oct 06 2017 Areas affected...Portions of southeast Nebraska...southwest Iowa...and far north central Kansas Concerning...Severe potential...Watch possible Valid 062014Z - 062145Z Probability of Watch Issuance...60 percent SUMMARY...Thunderstorms are expected to develop in the next 60-90 minutes in the vicinity of the frontal zone. Severe hail and brief gusty winds are the main threat. A watch may be needed by 21-22z. DISCUSSION...A mostly stationary frontal zone stretching from northwest Kansas into west-central Iowa will be the focus for thunderstorm development in the next 60-90 minutes. The most likely area for first initiation will be along the intersection of a weak surface trough and a differential heating boundary stretching between Concordia and Russell where GOES-16 1-min imagery shows cumulus steadily deepening. Shortly after the first CI in north-central Kansas, thunderstorms are expected to rapidly develop along the front into southeast Nebraska and southwest Iowa. Although extensive cloud cover south of the front has persisted, a very moist boundary layer and temperatures in the low 70s is still contributing to MLCAPE values of 500-1000 J/kg over southwest Iowa, and 1000-1500 J/kg over Nebraska and north-central Kansas. These values could increase somewhat as a steady northeastward advancement of the clearing should continue through the period. Deep-layer shear profiles are favorable for organized storms, including a few line segments and supercells capable of severe hail and brief severe wind gusts. While the low clouds have limited the magnitude of the low-level lapse rates -- and thus the potential for low-level stretching and a brief tornado -- wind speeds in the 500-1000 m layer are forecast to increase with time to produce fairly large low-level hodograph curvature in the unstable air. Based on RAP/HRRR model soundings, temperatures that warm into the upper 70s to near 80F could produce low-level lapse rates steep enough to increase the tornado threat. Otherwise, the severe threat will be mainly severe hail and brief severe wind gusts with any of the organized storms. Given the above expected evolution of storms, a severe weather watch may be needed in the next hour or two. ..Coniglio/Grams.. 10/06/2017 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...DMX...EAX...FSD...OAX...TOP...ICT...GID... LAT...LON 41159475 40469559 40209605 40039644 39679700 39439747 39209795 39129822 39099840 39159851 39349850 39839836 40329825 40879787 41229730 41569684 41869629 42119576 42339517 42429455 42209436 41889441 41159475
from SPC Mesoscale Discussions http://bit.ly/2z4x80j
Be First to Comment