SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0148 PM CST Sat Feb 27 2021

Valid 272000Z - 281200Z


Isolated strong to severe thunderstorms remain possible from eastern
Oklahoma to western Kentucky this evening and overnight.

...20Z Update...
No appreciable changes have been made to the ongoing forecast.
Elevated storms are expected to continue increasing in coverage this
afternoon/evening across parts of eastern OK into AR as low-level
warm advection strengthens in tandem with a south-southwesterly
low-level jet. This activity should eventually spread into southern
MO and the Mid-South tonight while posing an isolated threat for
marginally severe hail and perhaps a strong wind gust or two.
Generally weak instability should tend to limit the overall severe
threat, with convection remaining generally elevated.

..Gleason.. 02/27/2021

.PREV DISCUSSION... /ISSUED 1014 AM CST Sat Feb 27 2021/

A large-scale trough across the northern Rockies into the Great
Basin will continue to amplify and dig into the Four Corners today.
As this occurs, a lee trough/cyclone is expected to develop within
the southern/central High Plains. The rather diffuse cyclone will
progress to the northeast into the upper-Mississippi Valley region
by tomorrow morning. While height falls ahead of the trough will not
be overly strong, southerly low-level winds will increase along with
the trough/cyclone and ahead of a southeastward moving cold front
with accompanying warm front advancing northward in the Mid-South.

...Eastern Oklahoma into Western Kentucky...
Moisture return should continue to increase this afternoon and
evening across parts of eastern Oklahoma. Scattered storms are
expected to develop near the intersecting cold and warm fronts in
the vicinity of Fort Smith, AR and points southeastward. This
morning's observed regional soundings show mid-level lapse rates of
7-8 C/km. With strong deep-layer flow and MUCAPE near 1000 J/kg,
large hail will be possible with these elevated storms. A low-end
risk for damaging wind gusts will also exist given the relatively
shallow stable near-surface layer.

Farther east and north, deep-layer flow will be similarly strong,
but these areas will be farther removed from the steeper mid-level
lapse rates, reducing buoyancy. A risk for marginally severe hail
and damaging wind gusts will still exist. Towards tomorrow morning,
forecast soundings do indicate that low-level theta-e advection will
allow ongoing storms to become near surface-based meaning the threat
for damaging wind gusts may be maximized late in the period.

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