SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0158 PM CST Sun Feb 28 2021

Valid 282000Z - 011200Z


Damaging thunderstorm wind gusts, a few tornadoes, and large hail
will remain possible through tonight from northeast Texas into the
Mid-South and Tennessee Valley.

...20Z Update...
Severe probabilities have been reduced behind a southeastward-moving
cold front across parts of north-central/northeast TX and
southeastern OK. Convection is still expected to increase in both
coverage and intensity across AR into western/middle TN and northern
MS this afternoon and evening, with all severe hazards possible. For
more meteorological information on the short-term severe threat
across this region, see Mesoscale Discussion 136. Farther east into
central/northern AL and eastern TN, probabilities for damaging winds
and a couple tornadoes have been modestly expanded to account for a
line of storms along the cold front overnight that may still pose an
isolated severe risk.

..Gleason.. 02/28/2021

.PREV DISCUSSION... /ISSUED 1015 AM CST Sun Feb 28 2021/

A positively-tilted upper-level trough within the Four Corners
region will continue to sag southeastward today with a closed low
aloft eventually developing across AZ/NM. A broad swatch of strong
mid-level flow will exist from the Texas Big Bend into the Ohio
Valley and lower Great Lakes. At the surface, a cold front extends
from a central WI surface low southeastward into MO/OK and west TX.
The front will be the main focus for severe weather this afternoon.

...ARKLATEX into the Mid-South...
Upper 60s to around 70 F dewpoints are situated to the south of the
southeastward moving cold front. Broken cloud cover, particularly in
the ARKLATEX region has allowed temperatures to rise to the low 70s
F. Areas that continue to see broken cloud cover will support
1500-2000 J/kg of MLCAPE this afternoon. Effective shear values of
50-70 kts will support organized storm structures. Deep-layer shear
is generally parallel to the front and will generally favor linear
storm mode, though supercells ahead of and embedded within the line
are possible. Large hail will be possible, particularly early in the
convective cycle. An area of greater hail risk is evident within the
ARKLATEX given this morning's observed upstream mid-level lapse
rates. Very large hail will be possible in this region. Damaging
wind gusts will generally be the primary threat as convection
evolves and grows upscale along the boundary.

Low-level hodographs are supportive of a risk for tornadoes. Again,
the linear storm mode and the weakness in the flow around 700 mb in
both observed and forecast soundings should limit the overall
potential. However, a few embedded supercell and mesovortex
tornadoes within the convective line may occur.

...South TX...
A conditional threat for large hail will exist from the Edwards
Plateau into parts of South Texas. There is continuing uncertainty
with whether storms will develop based on the latest guidance.
However, deep-layer shear will be strong and forecast soundings
indicate very long hodographs. Should storms develop, they will
likely be elevated supercells behind the front.

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