Day 1 Severe Weather Outlook

Valid 281200Z – 291200Z

…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST
KANSAS TO THE ARKLATEX…AND EASTWARD TO THE MISSISSIPPI RIVER…

…SUMMARY…
Isolated severe storms are possible from I-35 in Oklahoma and
southeast Kansas eastward toward the Mississippi River through
tonight. Localized wind damage is most likely, although a brief
tornado cannot be ruled out.

…Synopsis…
An upper trough will move into the Plains with a lead wave moving
from west TX into OK during the day, and from eastern KS into IA
during the evening. Coincident with this shortwave trough will be
strong cooling aloft north of an intensifying mid to upper jet with
speeds of 100 to 150 kt respectively from eastern OK into MO.

At the surface, low pressure will deepen from western OK into
east-central KS during the day, with boundary-layer dewpoints
increasing into the mid 50s F ahead of a cold front and dryline. The
cold front should be near I-35 in KS by late afternoon, with a
dryline bulging into central OK. Aiding moisture transport will be
an intensifying low-level jet, with a 50 kt southerly 850 mb jet
expected from the Arklatex into MO by 00Z.

Meanwhile, dewpoints into the mid 60s F will be drawn north across
the lower MS Valley, well south of the upper wave but with a wind
shift approaching toward the end of the period.

…I-35 in OK and KS eastward to the MS River…
Scattered thunderstorms are likely to be ongoing at 12Z this morning
along the cold front, and near the developing surface low from
northwest TX into western OK. Forecast soundings indicate that most
of this activity will be elevated through about midday, when up to
500 J/kg SBCAPE is forecast to develop. Forcing for ascent will also
increase throughout the day, and early-day showers and storms may
slowly evolve into isolated strong or severe storms by late
afternoon. Several CAMs suggest consolidating line segments over
north-central OK and into southeast KS from late afternoon into the
evening, and this appears to be the most favorable area for
localized wind damage or perhaps a brief tornado. The threat is
highly conditional on instability, which could also be less than
forecast.

East of the KS/OK area, and during the evening and overnight, other
line segments, perhaps a loose QLCS, are expected to threaten parts
of southern MO and AR. Weak instability may prove sufficient to
support damaging wind gusts as shear will be very strong.

For far southern areas, including TX, LA, and MS, better low-level
moisture may interact with the front/wind shift after 03-06Z.
However, lift will be weak in these areas, though a few stronger
storms may produce locally gusty winds. A few pre-frontal storms are
also possible over northern MS into western TN where low-level
moisture will deepen beneath persistent southerly winds just off the
surface. Instability will again be the limiting factor as lapse
rates aloft will be poor, but veering wind profiles offer a
conditional threat of a severe storm.

..Jewell/Bentley.. 12/28/2019

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