Day 1 Severe Weather Outlook

Valid 261200Z – 271200Z


Severe thunderstorms are expected this afternoon through the evening
from the Middle Mississippi Valley region into eastern Kansas and
Oklahoma. Large hail, severe gusts, and a few tornadoes are
possible before the threat transitions to mainly a risk for severe
gusts and wind damage tonight.

…Lower MO Valley into OK…
A mid-level trough over the Upper Midwest today will evolve into a
closed low near the MN/Canada border by early Tuesday. A belt of
strong westerly 500mb flow will overspread the lower MO Valley
during the day. A complicating factor for this forecast will
involve an MCS over the north-central Plains which is forecast to
move into the lower MO Valley during the morning hours. Model
guidance generally depicts this scenario with some severe risk
perhaps ongoing early this morning before possibly waning with the
MCS dissipating over the lower MO Valley. Renewed storm development
is likely by late afternoon along a cold front forecast to move
southeast across the central Great Plains and lower MO Valley. The
intersection of possible earlier-day outflow with the front may
serve as a preferred storm initiation zone before additional storms
develop along the southwest-northeast oriented boundary. The
pre-convective airmass is forecast to become very unstable from
central OK northeast into eastern KS and MO with MLCAPE ranging from
3000-4000 J/kg. An initial window of opportunity (2 hours) may
exist for a supercell risk capable of all hazards. Precipitable
water around 2 inches and large CAPE, a wind profile strengthening
from the low into the midlevels (40-50kt) and weakening in the high
levels, and strong agreement of convection-allowing model guidance
all suggest a relatively quick transition to a linear band of storms
from northern MO zippering southwest into central OK during the
evening. Wind damage from severe gusts will likely become most
prevalent during the cellular to squall line transition (possible HP
supercells) and the initial 1-3 hours afterwards during the evening.
A gradual diminishing in storm intensity and potential severe
coverage is expected by late evening into the overnight as storms
move to the MS river and the Ark-La-Tex.

..Smith/Wendt.. 08/26/2019


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