000
ACUS11 KWNS 260400
SWOMCD
SPC MCD 260359
IAZ000-MNZ000-NEZ000-SDZ000-260530-

MESOSCALE DISCUSSION 0803
NWS STORM PREDICTION CENTER NORMAN OK
1059 PM CDT SAT MAY 25 2013

AREAS AFFECTED...NORTHWEST/CENTRAL/SOUTHEAST SD TO NORTHEAST
NEB/WESTERN IA/FAR SOUTHWEST MN

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 260359Z - 260530Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...TORNADO WATCH 217 WILL BE ALLOWED TO EXPIRE AS SCHEDULED
AT 04Z ACROSS PORTIONS OF SD/ND...BUT MAINLY A SEVERE HAIL
THREAT...AT LEAST ON AN ISOLATED BASIS...WILL LIKELY PERSIST INTO
THE OVERNIGHT ACROSS PORTIONS OF NORTHWEST/CENTRAL/SOUTHEAST SD AS
WELL AS NORTHEAST NEB/WESTERN IA/FAR SOUTHWEST MN. ALTHOUGH
QUESTIONS EXIST REGARDING THE MARGINALITY/DURATION OF THE SEVERE
RISK...A NEW SEVERE TSTM WATCH MAY NEED TO BE CONSIDERED ACROSS THE
REGION.

DISCUSSION...MAINLY ELEVATED STORMS PERSIST LATE THIS EVENING ACROSS
PORTIONS OF NORTHWEST-CENTRAL SD...WITH A MORE RECENT UPSWING IN
ELEVATED STRONG/SOME SEVERE CONVECTION ACROSS PORTIONS OF SOUTHEAST
SD/FAR NORTHEAST NEB INTO WESTERN IA/EXTREME SOUTHWEST MN. ALL OF
THIS ACTIVITY IS OCCURRING WITHIN A STRENGTHENING ISENTROPIC
ASCENT/WARM ADVECTION REGIME ALONG/NORTHEAST OF A
NORTHWEST-SOUTHEAST ORIENTED FRONTAL ZONE. THE SOURCE REGION AIRMASS
REMAINS RELATIVELY UNSTABLE...WITH 3000+ J/KG MUCAPE SAMPLED BY 00Z
OBSERVED SOUNDINGS ACROSS NEB /OMAHA AND NORTH PLATTE/. WHILE SEVERE
HAIL WILL REMAIN A POSSIBILITY MAINLY WITH ELEVATED STORMS THAT
ACQUIRE UPDRAFT ROTATION...SOME QUESTIONS EXIST REGARDING THE
PERCEIVED MARGINALITY AND UNCERTAIN SUSTAINABILITY OF THE SEVERE
THREAT THROUGH THE OVERNIGHT. THIS IS MAINLY ATTRIBUTABLE TO MODEST
MID-LEVEL FLOW WHICH MAY ULTIMATELY LEAD TO UPDRAFT
INTERFERENCE/CELL MERGERS OVER TIME.

..GUYER/THOMPSON.. 05/26/2013

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

ATTN...WFO...DMX...FSD...OAX...ABR...LBF...UNR...

LAT...LON   45850287 45700034 44099692 43069501 42059514 42149731
            43850017 44950219 45850287