Day 1 Severe Weather Outlook

Valid 091300Z – 101200Z

…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTH TEXAS
AND OKLAHOMA NORTHWARD TO EASTERN NEBRASKA/WESTERN IOWA…

…SUMMARY…
Isolated severe thunderstorms are possible late this afternoon and
evening across parts of north Texas and Oklahoma, and northward
overnight into the middle Missouri Valley.

…Oklahoma/Western North Texas to eastern Nebraska/western
Iowa…
In association with a mid-level shortwave trough/warm advection
regime, scattered showers/thunderstorms will continue to spread
east-northeastward across the region this morning, although severe
storms are not expected early today.

Appreciable lee-side cyclogenesis will occur across eastern Colorado
today, with a sharpening of the dryline/trough extending southward
into the southern High Plains. Although overall forcing for ascent
will be weak later this afternoon in the wake of the mid-level
trough, sufficient near-dryline mixing and confluence/convergence
should allow for isolated deeper convective development across parts
of Oklahoma/Texas, where a steady vertical mixing/influx of
low-level moisture will have occurred since morning.

The most likely corridor for isolated/widely scattered surface-based
thunderstorm development late this afternoon and early evening will
be across southwest Oklahoma and the Low Rolling Plains of western
North Texas, spanning locations from Elk City/Altus OK southward to
between Childress/Vernon TX. In this corridor, diurnal heating of
the moistening pre-frontal boundary layer should support 1000-1500
J/kg mixed-layer CAPE, sufficient to permit a few stronger/sustained
storms. Storm sustenance/longevity would be aided by a wind field
featuring veering/increasing flow with height, with
more-than-sufficient vertical shear (40 kt effective) for updraft
rotation.

Isolated instances of large hail should be the primary risk, with
strong winds possible as well. While low-level moisture will be
suboptimal and LCLs a bit high, a tornado risk cannot be ruled out
across southwest Oklahoma/nearby western North Texas as low-level
hodograph length/curvature increase toward sunset, prior to boundary
layer CINH becoming reestablished into mid/late evening.

A few strong-to-severe 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 these storms elevated atop a
fairly stable boundary layer, hail would be the primary severe risk,
with this potential possibly extending as far north as eastern
Nebraska/western Iowa tonight.

..Guyer/Dial.. 10/09/2019

$$

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