MESO: Mesoscale Discussion 1120

ACUS11 KWNS 181908
SWOMCD
SPC MCD 181907
COZ000-NEZ000-SDZ000-MTZ000-WYZ000-182100-

MESOSCALE DISCUSSION 1120
NWS STORM PREDICTION CENTER NORMAN OK
0207 PM CDT TUE JUN 18 2013

AREAS AFFECTED...ERN CO...ERN WY...EXTREME WRN NEB AND SERN MT

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 181907Z - 182100Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...STORMS MAY POSE A RISK FOR ISOLATED DAMAGING WIND AND
LARGE HAIL AS THEY SPREAD EWD OFF THE HIGHER TERRAIN INTO THE HIGH
PLAINS OF ERN CO...ERN WY AND SERN MT. TRENDS ARE BEING MONITORED
FOR A POSSIBLE SEVERE THUNDERSTORM WATCH.

DISCUSSION...OROGRAPHIC FORCING INDUCED BY DIABATIC WARMING OVER THE
MOUNTAINS HAS RESULTED IN THE DEVELOPMENT OF NUMEROUS STORMS FROM
THE CNTRL THROUGH NRN ROCKIES. TEMPERATURES ARE CLIMBING INTO THE
80S WITH LOW-MID 50S DEWPOINTS AND STEEP LAPSE RATES PROMOTING
MLCAPE FROM 1500-2000 J/KG. DEEPLY MIXED BOUNDARY LAYERS WITH 30+ F
TEMPERATURE-DEWPOINT SPREADS SUPPORT RELATIVE HIGH BASED STORMS.
THIS REGION RESIDES WITHIN AN UPPER RIDGE AXIS WITH GENERALLY WEAK
WINDS ALOFT. HOWEVER...BELT OF SLIGHTLY STRONGER FLOW AND UP TO
25-30 KT 0-6 KM SHEAR RESIDE OVER NRN WY...SERN MT AND SRN CO. THIS
SUGGESTS THE DOMINANT MODES SHOULD BE MULTICELLULAR AND STORMS MAY
EVENTUALLY EVOLVE INTO CLUSTERS SUPPORTED BY COLD POOL MERGERS AS
ACTIVITY MOVES OFF THE HIGHER TERRAIN. ISOLATED DAMAGING WIND AND
LARGE HAIL WILL BE POSSIBLE THROUGH MID EVENING.

..DIAL/THOMPSON.. 06/18/2013

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

ATTN...WFO...UNR...PUB...BOU...CYS...BYZ...RIW...

LAT...LON 45580695 43560618 41180539 38510481 38470319 40790326
45200465 45580695

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