MD 0655 CONCERNING SEVERE THUNDERSTORM WATCH 157… FOR CENTRAL/EASTERN NE…WESTERN/CENTRAL IA…FAR NORTHEAST KS/NORTHWEST MO
Mesoscale Discussion 0655
NWS Storm Prediction Center Norman OK
0620 PM CDT Wed Jun 06 2018
Areas affected...Central/Eastern NE...Western/Central IA...Far
Northeast KS/Northwest MO
Concerning...Severe Thunderstorm Watch 157...
Valid 062320Z - 070045Z
The severe weather threat for Severe Thunderstorm Watch 157
continues.
SUMMARY...The threat for large hail and damaging wind continues
across WW 157. Some upscale growth is possible with time into this
evening, with the threat expected to spread southward through the
watch.
DISCUSSION...At 2315Z, several severe thunderstorms are ongoing
along a surface boundary from eastern NE into central IA. The
environment across this region is characterized by strong
instability (MLCAPE of 2500-4000 J/kg) and weekly veering wind
profiles. Effective shear of 20-30 kt is marginal at best for
organized storm structures, though the westward propagating cell
north of Omaha has exhibited some supercell characteristics. In the
short term, the more discrete cells across eastern NE will pose a
threat of large hail (potentially greater than 2 inches in diameter
with any supercell structures) and locally damaging wind. Further
east, consolidation of outflows across western/central IA has
resulted in a southward acceleration of ongoing convection. The
storm mode is becoming less favorable for large hail in this area,
but more widespread damaging wind potential is possible as expanding
cold pools advance into a warm and moist airmass. A 62 kt gust was
noted in Ames, IA around 2230Z.
With time this evening, storms may consolidate over eastern NE and
begin propagating southward, spreading a threat of large hail and
damaging wind into southeast NE by mid-evening, while the Iowa
convection spreads a threat of wind and isolated severe hail into
southwest/south-central IA. There is some potential for the severe
threat to spread slightly eastward out of the watch in IA, and also
propagate slightly westward out of the watch in NE, though the
primary threat is expected to remain confined within WW 157 for at
least the next 1-2 hours.
..Dean.. 06/06/2018
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DVN...DMX...EAX...FSD...OAX...TOP...GID...LBF...
LAT...LON 42019884 42419484 42599263 42319189 41109227 40399467
39979558 39849695 39929782 40099837 40989883 42019884
from SPC Mesoscale Discussions http://bit.ly/2M2yfEa
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