Areas affected…southwestern Nebraska…northwestern Kansas…and
far eastern Colorado
Concerning…Severe potential…Watch likely
Valid 291944Z – 292145Z
Probability of Watch Issuance…80 percent
SUMMARY…Thunderstorms are expected to develop quickly after around
21Z or so, though convective trends are being monitored for a
potentially earlier initiation. A WW issuance will probably be
needed around the 21Z timeframe.
DISCUSSION…Latest observations and objective analyses indicate the
presence of a weak surface low near the KS/NE/CO border area, with a
slowly moving surface boundary located just north of the KS/NE state
line. Full insolation was occurring along this boundary and
southward across the warm sector beneath very steep (8.5C/km)
mid-level lapse rates, with point forecast soundings indicating
relatively weak inhibition and strong to extreme instability
(4000-5000 J/kg MUCAPE) amidst 60s to mid 70s F dewpoints.
Meanwhile, a weak shortwave trough was located across southern
Wyoming and vicinity and approaching the discussion area. Lift
associated with this wave and insolation was contributing to a
recent increase in cumulus across east-central Colorado and just
north of the boundary across southwestern Nebraska.
As the shortwave trough approaches the discussion area, sustained
surface convergence near the boundary and cooling aloft will remove
inhibition and result in scattered thunderstorm development.
Vertically veering and strengthening flow will promote some
organization in to loosely organized clusters over time – especially
as cold pools merge and mature. A brief tornado cannot be ruled out
especially along the surface boundary where easterly surface flow
will enhance low-level vorticity. Storms should gradually grow
upscale into one or two convective complexes and migrate
east-southeastward across the discussion area. Large hail and
severe wind (perhaps significant) will be the main threats with this
activity.
Given the forecast scenario, a WW issuance will probably be needed
by 21Z or so and will be coordinated with affected local forecast
offices.
..Cook/Thompson.. 08/29/2019
…Please see www.spc.noaa.gov for graphic product…
ATTN…WFO…GID…LBF…DDC…GLD…BOU…
LAT…LON 41110198 41330107 41059967 40289917 39089919 38359954
38220067 38400152 38970196 39760207 40570207 41110198