ZCZC SPCSWOMCD ALL
ACUS11 KWNS 202348 
SPC MCD 202348 
SDZ000-NEZ000-MTZ000-WYZ000-210115-

MESOSCALE DISCUSSION 0661
NWS STORM PREDICTION CENTER NORMAN OK
0648 PM CDT FRI MAY 20 2016

AREAS AFFECTED...NERN WY...SWRN SD...FAR NWRN NEB...FAR SERN MT

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 202348Z - 210115Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...AN ISOLATED HAIL THREAT WILL EXIST FOR THE NEXT 1-2 HRS
ACROSS PARTS OF THE NRN HIGH PLAINS INTO THE BLACK HILLS OF SD...BUT
COVERAGE WILL REMAIN SPARSE ENOUGH TO PRECLUDE WW ISSUANCE.

DISCUSSION...A PAIR OF SLOW-MOVING STORMS /DISPLAYING OCCASIONAL
SUPERCELL STRUCTURES/ OVER THE BLACK HILLS HAVE EXHIBITED THE
POTENTIAL FOR SVR HAIL OVER THE PAST 1-2 HRS...WITH A RECENT REPORT
OF 1.5 INCH HAIL RECEIVED FROM THE SRN-MOST STORM. ADDITIONAL
CONVECTION WAS DEVELOPING WITHIN A BROADER DIFFLUENT UPPER FLOW
PATTERN ACROSS THE HIGH PLAINS OF ERN WY. AN OUTFLOW BOUNDARY HAS
BECOME POSITIONED ALONG THE WRN SLOPES OF THE BLACK HILLS...WHILE
QUASI-STATIONARY FRONTAL SEGMENT EXTENDS FARTHER EWD...NOTED BY MORE
RECENT BACKING OF SFC WINDS NEAR/N OF I-90. 

STRONG DIURNAL HEATING FROM EARLIER TODAY HAS YIELDED MLCAPE VALUES
OF OVER 1000 J/KG...DESPITE THE PRESENCE OF MARGINAL MOISTURE WITHIN
THE BOUNDARY LAYER /40S TO LOW 50S F DEWPOINTS/. VWP DATA FROM UDX
SUGGESTS LOW-MIDLEVEL FLOW IS NOT PARTICULARLY STRONG...BUT ENHANCED
VEERING IN THE LOW LEVELS AMIDST ELY WINDS N OF THE QUASI-STATIONARY
FRONTAL SEGMENT WILL CONTINUE TO PROVIDE SUFFICIENT DEEP-LAYER SHEAR
FOR MARGINAL SUPERCELL STRUCTURES OVER THE BLACK HILLS. THE PRESENCE
OF COLD TEMPERATURES ALOFT AND STEEP MIDLEVEL LAPSE RATES...COMBINED
WITH DEEP VEERING WIND PROFILES...WILL CONTINUE TO SUPPORT ISOLATED
SVR HAIL POTENTIAL.

..ROGERS/EDWARDS.. 05/20/2016

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

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

LAT...LON   44830311 44110220 43530205 43040295 42580419 42750512
            43390597 44200577 44900571 45120508 45090373 44830311 

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