MESO: Mesoscale Discussion 1701

ACUS11 KWNS 122011
SWOMCD
SPC MCD 122010
SDZ000-MTZ000-WYZ000-122245-

MESOSCALE DISCUSSION 1701
NWS STORM PREDICTION CENTER NORMAN OK
0310 PM CDT MON AUG 12 2013

AREAS AFFECTED...PORTIONS OF CNTRL/ERN MT...FAR NRN WY...FAR NWRN SD

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 122010Z - 122245Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...ISOLATED SEVERE THUNDERSTORMS COULD DEVELOP BY LATE THIS
AFTERNOON.

DISCUSSION...SFC OBS REVEAL A CORRIDOR OF ENHANCED LOW-LEVEL
MOISTURE EXTENDING FROM THE LOWER PLAINS WNWWD/NWWD ACROSS THE MCD
AREA INTO N-CNTRL MT. THIS CORRIDOR LIES BETWEEN A DIFFUSE
NW/SE-ORIENTED SFC FRONT EXTENDING FROM NERN MT INTO SWRN ND AND
ANOTHER FRONT TO THE W IN THE LEE OF THE ROCKIES. SFC DEWPOINTS IN
THE MIDDLE AND UPPER 50S ARE COMMON ACROSS THE ENHANCED-MOISTURE
CORRIDOR...WITH READINGS IN THE LOWER 60S ACROSS PARTS OF N-CNTRL
MT. THE CONFIGURATION OF STEEP MID-LEVEL LAPSE RATES ACCOMPANYING AN
EML OVERLYING THE RELATIVELY RICH BOUNDARY-LAYER MOISTURE IS
CONTRIBUTING TO MLCAPE AROUND 1500-3000 J/KG PER MODIFIED 12Z
TFX/GGW RAOBS.

THE LATEST VISIBLE SATELLITE IMAGES INDICATE DIURNALLY
STRENGTHENING/DEEPENING OROGRAPHIC CIRCULATIONS AUGMENTED BY REGIONS
OF UPSLOPE FLOW SUPPORTING AGITATED CUMULUS/CONVECTIVE DEVELOPMENT
OVER TERRAIN-FAVORED AREAS. THIS INCLUDES THE MOUNTAINS OF S-CNTRL
MT AND NRN WY...AND MORE ISOLATED MOUNTAINS IN CNTRL MT --
E.G. LITTLE BELT AND BIG SNOWY MOUNTAINS.

AS THE CONVECTION DEVELOPS/SPREADS OFF THE HIGHER TERRAIN INTO
GREATER INSTABILITY...AND POTENTIALLY DEVELOPS ALONG A WIND-SHIFT
AXIS EXTENDING SWWD FROM THE INTERNATIONAL BORDER E OF CUT BANK...AN
ISOLATED SVR THREAT MAY EVOLVE. ELY LOW-LEVEL FLOW BENEATH AROUND
15-20 KT OF WSWLY MID-LEVEL FLOW MAY OFFER SUFFICIENT DEEP SHEAR TO
SUPPORT THE POTENTIAL FOR A FEW ORGANIZED/SUSTAINED CONVECTIVE
ELEMENTS WITH SVR WIND/HAIL POSSIBLE. HOWEVER...THE LACK OF STRONGER
FORCING FOR ASCENT THROUGH A DEEP LAYER MAY LARGELY MITIGATE THE
OVERALL COVERAGE/MAGNITUDE OF ANY SVR THREAT...AS MORE NOTABLE
MID-LEVEL IMPULSES REMAIN DISPLACED TO THE W OF THE CORRIDOR OF
ENHANCED LOW-LEVEL MOISTURE.

..COHEN/KERR.. 08/12/2013

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

ATTN...WFO...UNR...BYZ...GGW...RIW...TFX...

LAT...LON 44630546 44990808 45891063 47221189 48211199 48661138
48921018 48730716 46980510 45180364 44630546

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