Day 1 Severe Weather Outlook

Valid 091200Z – 101200Z


Isolated severe thunderstorms are possible on Wednesday afternoon
and evening across parts of north Texas and Oklahoma, and northward
overnight to the mid Missouri Valley area.

A high-amplitude flow field is progged to reside across the U.S.
today, as a large trough continues digging southeastward across the
interior West. Meanwhile, ridging will prevail east of the
Mississippi — although within the broader, background ridge, a
cut-off low is expected to linger across the mid-Atlantic/southern
New England area.

At the surface, high pressure will prevail over the East, while a
powerful cold front advances southeastward across the western half
of the country. This front — initially lying from the Dakotas
southwestward to the Great Basin, should arc from Minnesota to
central Kansas to the Texas Panhandle and across the Desert
Southwest by Thursday morning.

…North Texas/Oklahoma northward to eastern Nebraska/western
As a mid-level short-wave trough initially over the Kansas/Oklahoma
vicinity shifts northeastward toward the middle and upper
Mississippi Valley, accompanying/early-period convection should
likewise shift gradually northeastward. While weak subsidence is
expected in the wake of this system, isolated storm development may
occur over the western North Texas/southwestern Oklahoma region by
late afternoon/early evening along a surface trough/dryline. Here,
diurnal heating of the moistening pre-frontal boundary layer should
support 1000 to 1500 J/kg mixed-layer CAPE, sufficient to permit a
few stronger/sustained storms.

Presuming a few cells can develop, storm sustenance/longevity would
be aided by a wind field featuring veering/increasing flow with
height, sufficient for updraft rotation. As such, limited/isolated
severe risk remains evident, primarily in the form of hail.

A few storms may continue eastward across Oklahoma through the
evening, while farther north, isolated storms may develop, ahead of
the advancing cold front as low-level warm advection increases in
conjunction with a developing south-southwesterly low-level jet.
With the storms elevated atop a fairly stable boundary layer, hail
would be the primary severe risk — with this risk possibly
extending as far north as eastern Nebraska/western Iowa.

..Goss/Nauslar.. 10/09/2019


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