Mesoscale Discussion #46 (Watch Likely)

MESOSCALE DISCUSSION 0046
NWS STORM PREDICTION CENTER NORMAN OK
0537 PM CST SUN JAN 22 2012
AREAS AFFECTED...SERN MO...SRN IL...WRN KY...SWRN IND
CONCERNING...SEVERE POTENTIAL...WATCH LIKELY
VALID 222337Z - 230130Z
THUNDERSTORMS ARE FORECAST TO DEVELOP OVER SERN MO AND NERN AR
DURING THE 00-03Z TIME PERIOD...AND THEN MOVE QUICKLY DOWNSTREAM
ACROSS SRN IL...WRN KY AND SWRN IND DURING THE NIGHT. PRIMARY SEVERE
WEATHER THREAT WILL BE DAMAGING WINDS...THOUGH A FEW TORNADOES WILL
ALSO BE POSSIBLE.
SUBJECTIVE SURFACE ANALYSIS THIS EVENING PLACES A 993 MB LOW
POSITIONED OVER ERN KS...WITH A DRYLINE/PACIFIC COLD FRONT TRAILING
SWD INTO ERN OK AND NERN TX...AND A WARM FRONT EXTENDING E-NEWD INTO
SRN/CNTRL AR AND NRN MS. TEMPERATURES IN THE 70S AND DEWPOINTS IN
THE MID 60S EXIST S OF THE WARM FRONT...WHILE TEMPERATURES IN THE
50S AND 60S EXIST OVER THE MID-SOUTH ACCOMPANIED BY DEWPOINTS IN THE
UPR 40S TO MID 50S. IN ADDITION...A SECONDARY BAROCLINIC ZONE/PSEUDO
WARM FRONT EXTENDS NEWD OUT OF CNTRL AR TOWARD THE SRN IL/WRN KY
BORDER. AS A POTENT UPR LEVEL SHORTWAVE TROUGH EJECTS TOWARD THE MS
VALLEY TONIGHT...THE SURFACE LOW OVER KS IS FORECAST TO EJECT NEWD
ACROSS NRN MO INTO ERN IA/NRN IL. AS THIS OCCURS...MODEL GUIDANCE
INDICATES THE PRIMARY WARM FRONT WILL ATTEMPT TO LIFT NWD INTO WRN
KY...ALLOWING UPR 50S TO LOW 60S DEWPOINTS TO ADVECT INTO THE
REGION. MODEST SURFACE BASED CAPE MAY DEVELOP IN RESPONSE...RANGING
FROM 500-1000 J/KG.
MEANWHILE...THE PACIFIC COLD FRONT WILL ACCELERATE EWD ACROSS SRN MO
AND NRN AR DURING THE 00-06Z TIME PERIOD. STRONG FORCING FOR ASCENT
ASSOCIATED WITH THE SURFACE COLD FRONT AND UPR TROUGH...AS WELL AS
MORE SUBTLE ASCENT ALONG BOTH THE PRIMARY AND PSEUDO WARM FRONTS
WILL LEAD TO AN INCREASING PROBABILITY FOR THUNDERSTORM INITIATION
DURING BY 00-03Z TIME PERIOD OVER NERN AR/SERN MO AND POSSIBLY WRN
KY/SRN IL. STRONG VEERING DEEP LAYER TROPOSPHERIC
FLOW...CHARACTERIZED BY 70+ KT SWLY MIDLEVEL JET JUXTAPOSED ABOVE A
50+ KT S-SWLY LLJ WILL FAVOR FAST NELY STORM MOTIONS FROM 40-60 KT.
THE STRONG FLOW COMBINED WITH STRONG FORCING FOR ASCENT SHOULD
SUPPORT STORM CLUSTERS AND LINES POSING A DAMAGING WIND THREAT. IN
ADDITION...VERY LARGE 0-3 KM HODOGRAPH CURVATURE /WITH 0-1 KM SRH
AOA 400 M2 S-2/ WILL PROMOTE EMBEDDED SUPERCELLS AND A THREAT FOR A
FEW TORNADOES. PRIMARY CONCERN REGARDING THE TORNADO THREAT IS
MARGINAL BOUNDARY LAYER THERMODYNAMICS /I.E. SLIGHTLY COOL NEAR
SURFACE TEMPERATURES/. HOWEVER...IF OBSERVATIONAL TRENDS SUGGEST
SURFACE BASED THUNDERSTORMS WILL BE LIKELY...THEN WATCH TYPE WILL BE
TORNADO.