MESO: Mesoscale Discussion 1708

ACUS11 KWNS 131837
SWOMCD
SPC MCD 131836
SDZ000-NDZ000-MTZ000-WYZ000-132100-

MESOSCALE DISCUSSION 1708
NWS STORM PREDICTION CENTER NORMAN OK
0136 PM CDT TUE AUG 13 2013

AREAS AFFECTED...PORTIONS OF SERN MT...FAR SWRN ND...WRN SD...NERN
WY

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 131836Z - 132100Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...THE POTENTIAL FOR SVR THUNDERSTORMS MAY INCREASE THIS
AFTERNOON...AND THE AREA IS BEING MONITORED FOR THE POSSIBLE
ISSUANCE OF A WW.

DISCUSSION...VISIBLE SATELLITE IMAGERY DEPICT A WELL-DEFINED MCV
CENTERED NEAR THE MUTUAL INTERSECTION POINT OF THE ND/SD/MT BORDERS.
THE AUGMENTATION TO TROPOSPHERIC KINEMATIC FIELDS OWING TO THIS
PERTURBATION IS ENHANCING ASCENT OVER ITS SRN FLANK SUCH THAT
CONVECTION CONTINUES TO INCREASE IN COVERAGE/INTENSITY FROM CARTER
COUNTY MT INTO HARDING COUNTY ND PER 7- AND 9-KM CAPPI RADAR DATA.

ADDITIONAL CONVECTION MAY INCREASE ACROSS THE MCD AREA DURING THE
NEXT FEW HOURS -- AIDED BY FORCING FOR ASCENT AROUND THE
MCV...DIFFERENTIAL-HEATING-INDUCED BAROCLINICITY ACCOMPANYING A
MULTI-LAYERED CLOUD SHIELD THAT BRANCHES SE OF THE MCV INTO NWRN
SD...AND IN RESPONSE TO STRENGTHENING OROGRAPHIC CIRCULATIONS AROUND
THE BLACK HILLS.

A CORRIDOR OF LOWER-60S SFC DEWPOINTS LIES ACROSS THE AREA BETWEEN A
FRONT IN THE LEE OF THE ROCKIES...AND DRIER/CONTINENTAL AIR FARTHER
W. DIURNAL HEATING OF THIS MOISTURE BENEATH RELATIVELY STEEP
MID-LEVEL LAPSE RATES -- AROUND 7 CM/KM IN THE 700-500-MB LAYER PER
12Z RAP/GGW RAOBS -- IS SUPPORTING MLCAPE AROUND 1000-2500 J/KG.
AND...WITH EFFECTIVE BULK SHEAR MAGNITUDES AROUND 20-30 KT -- WITH
DEEP SHEAR AIDED BY A VERTICALLY VEERING WIND PROFILES IN THE LOW
LEVELS PER AREA VWP DATA -- A FEW ORGANIZED...SEWD-MOVING CONVECTIVE
CLUSTERS WITH SVR HAIL/WIND MAY ENSUE. ATTM...THERE IS UNCERTAINTY
REGARDING THE OVERALL COVERAGE OF SUCH SVR THREAT...OWING TO THE
ABSENCE OF A MORE SALIENT/LARGER-SCALE MECHANISM FOSTERING ASCENT
THROUGH A DEEP LAYER. REGARDLESS...TRENDS WILL CONTINUE TO BE
MONITORED.

..COHEN/KERR.. 08/13/2013

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

ATTN...WFO...BIS...UNR...CYS...BYZ...

LAT...LON 45580495 46040351 45040171 43850134 43190201 43250407
45580495

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