ZCZC SPCSWOMCD ALL
ACUS11 KWNS 221955 
SPC MCD 221955 
IAZ000-MOZ000-KSZ000-NEZ000-222100-

MESOSCALE DISCUSSION 1733
NWS STORM PREDICTION CENTER NORMAN OK
0255 PM CDT SAT AUG 22 2015

AREAS AFFECTED...ERN NEB...SWRN IA...NWRN MO...NERN KS

CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 

VALID 221955Z - 222100Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...TSTM INITIATION IS EXPECTED BY 21Z...WITH AN INITIAL
THREAT OF SUPERCELLS CAPABLE OF LARGE HAIL...DAMAGING WINDS...AND A
COUPLE OF TORNADOES. TORNADO WATCH ISSUANCE IS LIKELY BY 20Z.

DISCUSSION...A POWERFUL UPPER TROUGH IS NOW MOVING INTO THE WRN
DAKOTAS...WITH AN ASSOCIATED 998 MB SFC LOW LOCATED OVER SRN SASK
AND A TRAILING COLD FRONT MOVING THROUGH THE DAKOTAS INTO CNTRL NEB.
VERY STEEP LAPSE RATES /AS INDICATED BY THE 18Z OAX RAOB/ COMBINED
WITH A WARM/MOIST BOUNDARY LAYER IS RESULTING IN STRONG
BUOYANCY...WITH MLCAPE RISING INTO THE 2000-3000 J/KG RANGE. WHILE
MIDLEVEL FLOW IS SOMEWHAT MODEST...VEERING WIND PROFILES ARE
SUPPORTING EFFECTIVE SHEAR OF 30-35 KTS AND EFFECTIVE SRH OF 150-200
M2/S2...SUFFICIENT FOR ORGANIZED STORM STRUCTURES GIVEN STRONG
INSTABILITY. 

SOME UNCERTAINTY REMAINS REGARDING THE TIMING AND COVERAGE OF
INITIATION WITH SWRN EXTENT...BUT STRONG ASCENT ALONG THE COLD FRONT
SHOULD QUICKLY ERODE THE CAP AND ALLOW FOR INITIATION ACROSS
E-CNTRL/SERN NEB INTO WRN IA BY 21Z. A FEW SUPERCELLS WILL BE
POSSIBLE WITHIN 1-2 HRS OF INITIATION...WITH A THREAT OF VERY LARGE
HAIL AND A COUPLE OF TORNADOES. UPSCALE GROWTH IS EXPECTED WITH
TIME...GIVEN STRENGTH OF ASCENT SPREADING OVER THE REGION...WITH A
MORE FOCUSED DAMAGING WIND THREAT BECOMING POSSIBLE ACROSS PARTS OF
SERN NEB/SWRN IA INTO NERN KS/NWRN MO THIS EVENING. 

GIVEN THE ABOVE CONCERNS...TORNADO WATCH ISSUANCE IS LIKELY BY 21Z
ACROSS THE AREA.

..DEAN/CORFIDI.. 08/22/2015

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

ATTN...WFO...DMX...EAX...OAX...TOP...ICT...GID...

LAT...LON   40219895 41019780 41679702 42119665 42159613 42159548
            42159492 42139424 42169318 40849384 40139416 39689448
            39439507 38999813 40219895 

NNNN