5/6 Oklahoma/Kansas severe weather - High Risk- PDS Tor Watch

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...Synopsis...
A potent shortwave trough is evident in water vapor imagery this
evening within the Great Basin. This feature will continue eastward
into the Four Corners by early this morning. An initial speed max is
expected to eject into western Kansas. By late afternoon into the
evening, another speed max will approach western Oklahoma. Deep
low-level moisture is already being observed in the BRO 00Z
sounding. Surface observations also show low 70s dewpoint as far
north as the DFW Metroplex this evening. As the trough approaches,
this moisture should stream northward. The overall synoptic setup
indicates a severe weather outbreak occurring this afternoon and
extending into the evening and parts of the overnight period.
Multiple intense, long-track tornadoes are expected, especially in
parts of southern Kansas into Oklahoma. Very-large hail of up 2-4
inches can also be expected with intense supercells. Severe gusts
may initially be isolated, but storm coverage should increase with
time as well as the mode becoming more linear. As this occurs,
severe gusts, some up to 80 mph, will become more common.

...Oklahoma into southern Kansas...
Intense storms are expected across these areas by late afternoon.
Storm coverage is likely to initially be greatest in south-central
Kansas given the greater and earlier upper-level forcing. Isolated
storms will still be possible along the dryline in western Oklahoma
as strong heating in the Texas Panhandle should support dryline
circulations that should at least locally erode inhibition. By the
evening, greater forcing for ascent will arrive in western Oklahoma.
Flow aloft will be nearly perpendicular to the dryline, which will
favor a discrete storm mode. Even as the weak Pacific front
overtakes the dryline, low-level forcing is not expected to be
strong enough to promote substantial upscale growth, especially when
coupled with continued strong shear across the boundary.

Overall, there appears to be prolonged opportunity for discrete
storms to form across western Oklahoma into parts of southern
Kansas. While the environment during the afternoon will certainly
support intense, long-track tornadoes, concern only grows by early
evening. Discrete storms are expected to move eastward into an
intensifying low-level jet core in central and eastern Oklahoma into
southeast Kansas. Surface-based activity will likely persist into
the evening and even parts of the overnight, given continued influx
of moisture and weak capping. The time frame of greatest concern for
intense tornadoes is from 03-06Z across central into northeast
Oklahoma.

This is a high-end environment. An upgrade to a tornado-driven High
Risk was considered. There remains some lingering uncertainty with
regard to the number of intense tornadoes that will occur. An
increase in tornado probabilities will certainly be warranted should
confidence in coverage and preferred corridors increase.

...Western Kansas into Nebraska...Iowa...Missouri...
Convection will likely initiate in western Kansas into southwest
Nebraska earlier than elsewhere given the timing of the upper-level
forcing. Furthermore, a linear mode should more quickly become
established due to the deep layer shear being oriented much more
parallel to the initiating boundary than farther south. Buoyancy
will generally decrease with northward extent. That being said,
moisture will continue to push northward through the day and into
the evening. Mid 60s F dewpoints could reach southeast Nebraska.
Strong deep-layer and low-level shear will promote an organized line
of convection capable of wind damage and QLCS tornadoes (some
potentially strong). There is some potential for discrete storms to
form ahead of the anticipated line. These storms would pose a
greater threat for significant tornadoes. Large to very large hail
will likely be more likely in western and central Kansas and
coverage of very large hail will be conditional on how long a
discrete mode is maintained.

...South Dakota...
Richer low-level moisture (upper 50s to perhaps near 60 F dewpoints)
will reach portions of central into northwest South Dakota. A narrow
zone of instability is expected to develop by the afternoon between
the cold and warm front. Large hail and severe gusts will be the
main threats, but low-level shear will be sufficient for a tornado
or two.

...Edwards Plateau into Texas Rolling Plains...
Storm coverage this far south should generally be much more isolated
on account of weak and nebulous forcing. However, a strong enough
dryline circulation could initiate convection within a strongly
unstable and sheared environment. Should storms form, large hail and
severe wind gusts would be possible.

..Wendt/Darrow.. 05/06/2024

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