MESO: Mesoscale Discussion 1740

ACUS11 KWNS 201947
SWOMCD
SPC MCD 201947
MNZ000-SDZ000-NDZ000-202215-

MESOSCALE DISCUSSION 1740
NWS STORM PREDICTION CENTER NORMAN OK
0247 PM CDT TUE AUG 20 2013

AREAS AFFECTED...A LARGE PART OF SD...SERN ND...NWRN/W-CNTRL/N-CNTRL
MN

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 201947Z - 202215Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...AN ISOLATED...MARGINAL SVR POTENTIAL MAY DEVELOP DURING
THE NEXT COUPLE OF HOURS AND PERSIST INTO THE EVENING.

DISCUSSION...DIURNAL HEATING IS CONTRIBUTING TO A REDUCTION IN
CAPPING ACCOMPANYING A WARM EML OVERLYING THE AREA AS SFC TEMPS HAVE
INCREASED INTO THE MIDDLE 80S TO THE LOWER 90S...WITH A MODIFIED 12Z
RAP RAOB INDICTING REMAINING MLCINH LESS NEGATIVE THAN -50 J/KG.
ASCENDING BRANCHES OF OROGRAPHIC CIRCULATIONS INVOF THE BLACK HILLS
HAVE BEEN BOLSTERED BY AN IMPINGING FRONTAL CIRCULATION TO SUPPORT A
RECENT UPTICK IN CONVECTION OVER ELEVATED HEAT SOURCES. STRONGER
CONVECTION COULD EVOLVE FROM THIS ACTIVITY DURING THE NEXT COUPLE OF
HOURS AND ADVANCE OVER THE LOWER ELEVATIONS TO THE E/SE. ISOLATED
CONVECTION MAY ALSO BLOSSOM FROM A REGION OF PATCHY ACCAS AROUND THE
MUTUAL INTERSECTION POINT OF THE ND/SD/MN BORDERS...AND FROM A
BOUNDARY-LAYER CUMULUS FIELD BECOMING AGITATED AND CONCENTRATED
INVOF A PRE-FRONTAL CONFLUENCE AXIS ANALYZED OVER N-CNTRL MN.

WHILE STEEP MID-LEVEL LAPSE RATES ACCOMPANYING THE AFOREMENTIONED
EML WILL CONTRIBUTE TO LARGE CONDITIONAL BUOYANCY OWING TO SFC
DEWPOINTS GENERALLY IN THE 60S...THE COMBINATION OF LACKING DEEP
FORCING FOR ASCENT AND THE ONGOING EML-RELATED CAP SHOULD KEEP
CONVECTION/THE SVR THREAT SPARSE IN COVERAGE...AND COULD BE
DELETERIOUS FOR THE MAINTENANCE OF VIGOROUS/PERSISTENT UPDRAFTS.
REGARDLESS...WITH MLCAPE AROUND 1500-3000 J/KG AND MODEST MID-LEVEL
FLOW -- AS SAMPLED BY REGIONAL VWP DATA -- SUPPORTING AROUND 25-40
KT OF EFFECTIVE BULK SHEAR...ANY SUSTAINED/ORGANIZED CONVECTIVE
ELEMENTS COULD PRODUCE MARGINALLY SVR HAIL/WIND THIS AFTERNOON INTO
THIS EVENING.

..COHEN/CORFIDI.. 08/20/2013

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

ATTN...WFO...DLH...MPX...FGF...FSD...ABR...BIS...UNR...

LAT...LON 43790362 44290386 45050288 47559811 48729487 48669352
48129295 46829383 45219604 43789948 43500252 43790362

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