Mesoscale Discussion 0961
NWS Storm Prediction Center Norman OK
0659 PM CDT Sun Jun 21 2020
Areas affected...Parts of central into eastern Nebraska...western
Iowa...and extreme southeast South Dakota
Concerning...Severe Thunderstorm Watch 291...
Valid 212359Z - 220200Z
The severe weather threat for Severe Thunderstorm Watch 291
continues.
SUMMARY...The severe threat continues across Severe Thunderstorm
Watch 0291, with a recent uptick in convective coverage/intensity
noted. Large hail appears to be the primary threat. A couple of
severe gusts will also be possible with the stronger, longer lasting
storms.
DISCUSSION...Relatively robust convective initiation has recently
been noted across portions of central NE, with convection struggling
to intensify farther northeast near the NE/SD/IA border area. The
newer storms across central NE will continue to develop along the
I-80 corridor for at least the next few hours. 7.5 C/km mid-level
lapse rates (per latest Mesoanalysis) suggest that the most robust
updrafts will support severe hail potential, with KUEX
dual-polarimetric and mosaic MRMS data suggesting occasional severe
hail occurring. A few severe gusts also cannot be ruled out.
However, despite up to 2000 J/kg MLCAPE present, low-level shear
remains relatively poor. With modest (i.e. 35 knot) effective bulk
shear in place, individual storms (including transient supercells)
may struggle to sustain themselves longer than 2-3 hours, as noted
by the last few HRRR deterministic and Warn-on-Forecast ensemble
forecasts. After sunset, nocturnal cooling is expected to encourage
gradual weakening of any storms that remain.
..Squitieri/Thompson.. 06/21/2020
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DMX...FSD...OAX...GID...LBF...GLD...
LAT...LON 39840020 41509995 42859783 43699524 42469488 41459536
40619638 40079733 39840020
Read morefrom SPC Forecast Products http://www.spc.noaa.gov/products/md/md0961.html
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