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ACUS11 KWNS 291525
SWOMCD
SPC MCD 291525=20
ARZ000-LAZ000-TXZ000-OKZ000-291730-

Mesoscale Discussion 2070
NWS Storm Prediction Center Norman OK
0925 AM CST Wed Dec 29 2021

Areas affected...portions of far southeast OK...northeast
TX...southern AR...and northern LA

Concerning...Severe potential...Watch possible=20

Valid 291525Z - 291730Z

Probability of Watch Issuance...60 percent

SUMMARY...Severe thunderstorm potential is increasing across parts
of the ArkLaTex vicinity. A watch may be needed by 17z.

DISCUSSION...A quasi-stationary boundary extends from west to east
across parts of far north Texas into southern AR and western TN at
15z. Isolated, mainly elevated, thunderstorms are ongoing across
eastern OK into north Texas along the Red River in a strong warm
advection regime ahead of a surface low located northwest of the
Dallas-Ft. Worth Metroplex. To the south of the boundary, surface
dewpoints are mainly in the mid 60s to near 70 F. Steep midlevel
lapse rates near 8.0 C/km were noted in the 12z FWD RAOB, with more
modest values around 6.5-7 C/km noted downstream. Rich warm sector
moisture beneath moderate midlevel lapse rates is resulting in
MLCAPE values around 500-1000 J/kg already this morning. Visible
satellite imagery also shows a broad, agitated CU field across the
ArkLaTex vicinity with vertical development apparent in short-term
loops.=20

Mid/upper forcing associated with an ejecting shortwave trough over
the OK/TX Panhandles will remain somewhat limited. However,
thunderstorm coverage is expected to increase by around 17-18z as
the surface low develops eastward along the frontal wave and a 35-45
kt low level jet overspreads the region. Effective shear magnitudes
greater than 50 kt and favorably curved low-level hodographs will
support isolated supercell structures capable of strong gusts and a
tornado or two. Additionally, the KFWS VWP indicates an elongated,
straight hodograph in mid and upper levels, and combined with
moderate midlevel lapse rates, stronger storms may also produce
severe hail. Convective trends are being monitored and a watch may
be needed for portions of the MCD area in the next hour or two.

..Leitman/Hart.. 12/29/2021

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!pQKG-SX60JZoUX7y1ph9twWRRZhgW17sfLkIm2hueRGGpKBT79irYUUp9yyEeTMW-utGeh_g$=
for graphic product...

ATTN...WFO...JAN...LZK...SHV...

LAT...LON 33079500 33629506 33859487 34009454 34279381 34379315
34359250 34189206 33649171 33179175 32639210 32489267
32459339 32509416 32659468 33079500=20



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