SWOMCD
SPC MCD 241925
SDZ000-NEZ000-COZ000-MTZ000-WYZ000-242030-
MESOSCALE DISCUSSION 1375
NWS STORM PREDICTION CENTER NORMAN OK
0225 PM CDT FRI JUN 24 2011
AREAS AFFECTED...CNTRL/ERN WY...SERN MT...FAR WRN SD...FAR WRN
NEB...FAR NRN CO
CONCERNING...SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY
VALID 241925Z - 242030Z
SVR STORMS WITH DMGG WINDS AND LARGE HAIL WILL BE POSSIBLE THIS
AFTERNOON INTO THE EVENING.
SOME INCREASE IN MID-LEVEL ASCENT IS BEING MANIFEST IN THE
DEVELOPMENT OF INTENSE CONVECTION CURRENTLY OVER THE BIG HORN BASIN.
ADDITIONAL DEVELOPMENT IS NOTED FARTHER SOUTH INTO CNTRL WY...WHERE
AN AREA OF ENHANCED SFC PRESSURE FALLS IS PRESENT AS THE LOW-LEVEL
MASS FIELDS RESPOND TO THE AFOREMENTIONED ASCENT. THIS ACTIVITY WILL
CONTINUE TO BE MAINTAINED OVER THE NRN/NERN PERIPHERY OF A PLUME OF
STEEP MID-LEVEL LAPSE RATES /700-500-MB LAPSE RATE OF 8.1 C PER KM
ACCORDING TO THE 12Z RIVERTON SOUNDING/...AS IT MOVES EWD ACROSS
PORTIONS OF WY. ADDITIONAL CONVECTIVE DEVELOPMENT IS ANTICIPATED IN
RESPONSE TO FRONTAL CONVERGENCE INVOF A COLD FRONT DRAPED ACROSS
PORTIONS OF ERN/SRN MT INTO NWRN WY...AND IN RESPONSE TO OROGRAPHIC
INFLUENCES /A BUILDING CUMULUS FIELD ALREADY NOTED NEAR THE S-CNTRL
WY MOUNTAINS PER RECENT VISIBLE SATELLITE IMAGERY/. MODEST LOW-LEVEL
MOISTURE -- I.E. SFC DEWPOINTS FROM THE UPPER 40S ACROSS CNTRL WY TO
THE UPPER 50S ACROSS PORTIONS OF WRN SD AND WRN NEB -- WILL ALSO
SERVE TO ENHANCE UPWARD PARCEL BUOYANCY...WITH MLCAPE VALUES OF 1000
TO 1500 J/KG ALREADY COMMON. EFFECTIVE BULK SHEAR MAGNITUDES OF 35
TO 45 KT COULD SUPPORT HIGH-BASED SUPERCELL STORMS WITH AN ATTENDANT
THREAT FOR DMGG WIND GUSTS AND LARGE HAIL. AS THE ACTIVITY SHIFTS
EWD TOWARD THE HIGH PLAINS AND ENCOUNTERS RICHER LOW-LEVEL
MOISTURE...THE SVR THREAT COULD INCREASE. TEMPERATURE-DEWPOINT
SPREADS IN EXCESS OF 20F WILL LIKELY HINDER ANY TORNADO THREAT
THROUGH LATE AFTERNOON. WHILE A LOCALIZED TORNADO THREAT /ALBEIT
LOW/...COULD ENSUE OVER THE HIGH PLAINS BY EARLY EVENING ONCE
TEMPERATURE-DEWPOINT SPREADS DECREASE AND CONVECTION ENCOUNTERS
NOTABLE DIRECTIONAL SHEAR...OVERALL WEAK LOW-LEVEL FLOW WILL LIKELY
REDUCE HODOGRAPH LENGTH AND EFFECTIVE SRH VALUES THUS MITIGATING THE
TORNADO THREAT.
..COHEN.. 06/24/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...UNR...BOU...CYS...BYZ...RIW...
LAT...LON 40960582 42390788 44570898 45500749 45700538 45020381
43170310 40970345 40960582
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