MESO: Mesoscale Discussion 1977

ACUS11 KWNS 210545
SWOMCD
SPC MCD 210545
ARZ000-MOZ000-OKZ000-210745-

MESOSCALE DISCUSSION 1977
NWS STORM PREDICTION CENTER NORMAN OK
1245 AM CDT FRI SEP 21 2012

AREAS AFFECTED...OZARK PLATEAU

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 210545Z - 210745Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...A MARGINAL SEVERE HAIL THREAT MAY DEVELOP WITH ELEVATED
CONVECTION LIKELY INCREASING IN COVERAGE DURING THE NEXT SEVERAL
HOURS.

DISCUSSION...ELEVATED CONVECTION HAS FORMED ACROSS SWRN MO WITHIN A
CORRIDOR OF LOW-LEVEL WARM THETA-E ADVECTION. WITH BASES ROOTED
AROUND 750-725 MB PER METAR CEILING HEIGHTS...THIS DEVELOPMENT IS
OCCURRING ON THE PERIPHERY OF WEAK ELEVATED BUOYANCY WITH MUCAPE AOB
1000 J/KG. ALTHOUGH STRONG LOW-LEVEL SHEAR EXISTS BELOW THE CLOUD
BASE...NEARLY UNIDIRECTIONAL W/NWLYS IN THE CLOUD-BEARING LAYER AND
ONLY MODEST SPEED SHEAR SHOULD MITIGATE ROBUST UPDRAFT ROTATION. 00Z
WRF-NSSL/NMM RUNS WERE A BIT SLOW WITH DEVELOPMENT...BUT THEIR
SCENARIO APPEARS REASONABLE WITH CONVECTION GROWING UPSCALE INTO A
CLUSTER. THIS TYPE OF MODE AND LACK OF STRONGER CLOUD-BEARING SHEAR
SHOULD MITIGATE LARGER HAIL GROWTH.

..GRAMS/CARBIN.. 09/21/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PAH...MEG...LSX...LZK...SGF...TSA...

LAT...LON 36999449 37319293 37189109 37009047 36509055 36169102
35889186 35779262 35759393 35939463 36309494 36999449

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