Valid 101630Z – 111200Z
…THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
AND EVENING OVER PARTS OF SOUTHERN SOUTH DAKOTA AND NORTHERN
NEBRASKA…
…SUMMARY…
An enhanced threat for severe hail and wind should develop this
afternoon and evening across parts of the north-central Plains,
mostly near the Nebraska/South Dakota line. A tornado threat exists
in that area as well.
…Central/Northern High Plains…
A shortwave trough currently moving across UT will track into the
central and northern High Plains this evening. Model guidance
suggests that midlevel height falls and lift will overspread parts
of western WY and the NE Panhandle after 18z, with convective
initiation occurring a few hours afterward. Storms will be focused
along a surface baroclinic zone that extends from northeast WY
southeastward into the NE Panhandle – then eastward across NE.
Forecast soundings in vicinity of the boundary show MLCAPE values
around 3000 J/kg and a weak cap. Initial storm structures will
likely be supercellular, with a risk of very large hail and isolated
tornadoes. A consensus of CAM solutions agree that storms will
congeal and grow upscale through the evening as they track eastward
along the boundary across NE, with a focused area of enhanced
damaging wind threat.
…ID/UT/WY/MT…
Scattered thunderstorms are expected to intensify early this
afternoon beneath the core of the midlevel shortwave trough over
northern UT and southeast ID. These storms will be relatively
fast-moving and in a steep lapse rate environment. The strongest
cells in this region will pose a risk of hail and damaging wind
gusts. Some activity may remain strong as it moves across
northern/western WY into southern MT this evening.
…Western KS into northeast NM…
Full sunshine will lead to an axis of moderate CAPE values this
afternoon along the dryline from western KS into northeast NM. All
model guidance shows the development of isolated thunderstorms in a
deeply mixed but weakly sheared environment. A few of the storms
will be capable of strong downburst winds for a few hours this
afternoon and evening.
…Lower MI…
A weak convectively-enhanced upper trough is moving across WI. This
feature will move eastward into Lower MI this afternoon, with
scattered thunderstorms likely to form. Rather strong winds aloft
and sufficient CAPE suggest a risk of gusty/damaging winds in the
strongest cells.
..Hart/Wendt.. 09/10/2019
$$