[MCD] SWOMCD

Sat May 21 05:58:29 UTC 2005

ACUS11 KWNS 210608
SWOMCD
SPC MCD 210608 
MNZ000-SDZ000-NDZ000-210745-

MESOSCALE DISCUSSION 0947
NWS STORM PREDICTION CENTER NORMAN OK
0108 AM CDT SAT MAY 21 2005

AREAS AFFECTED...SRN ND/NRN SD

CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

VALID 210608Z - 210745Z

A NEW WW WILL BE REQUIRED WITHIN THE HOUR TO REPLACE WW 305 EXPIRING
AT 07Z.

LATEST MESOANALYSIS INDICATED A DEEPENING SURFACE LOW OVER NWRN SD
/SW OF REJ/ WITH ATTENDANT WARM FRONT EXTENDING EWD NEAR THE ND/SD
BORDER. AS OF 0550Z...CLUSTERS OF STRONG TO POTENTIALLY SEVERE TSTMS
WERE IN PROGRESS OVER GARFIELD...ROSEBUD...CUSTER AND POWDER RIVER
COUNTIES IN ERN MT...AS WELL AS EDMUNDS AND FAULK COUNTIES IN
N-CNTRL/NERN SD. THE FORMER STORMS APPEAR TO BE ASSOCIATED WITH COLD
FRONT STEADILY PUSHING EWD ACROSS ERN MT. RUC FORECAST SOUNDINGS AND
PLAN VIEW DIAGNOSTIC FIELDS...INDICATE THAT DOWNSTREAM AIR MASS
ACROSS NWRN SD INTO SWRN ND REMAINS MODERATELY UNSTABLE /MUCAPES OF
1500-2500 J/KG/ WITH VERY STEEP MID-LEVEL LAPSE RATES OF 8.5 - 9
C/KM. GIVEN STRONG SHEAR PROFILES ALREADY IN PLACE AHEAD OF VIGOROUS
SHORTWAVE TROUGH LIFTING NEWD THROUGH THE NRN ROCKIES...POTENTIAL
WILL EXIST FOR ORGANIZED SEVERE STORMS...INCLUDING SUPERCELLS/BOWING
STRUCTURES EWD FROM VICINITY OF SURFACE LOW ALONG WARM FRONT. THE
STEEP LAPSE RATES COUPLED WITH AVAILABILITY OF DRY AIR BETWEEN 3 KM
AGL AND SHALLOW NEAR SURFACE INVERSION SUGGESTS THE POTENTIAL FOR
COLD POOL ORGANIZATION AND POSSIBLE UPSCALE GROWTH INTO A
FORWARD-PROPAGATING MCS.

MEANWHILE...THE LATTER STORMS OVER N-CNTRL/NERN SD ARE LIKELY
ASSOCIATED WITH STRONG WAA/ISENTROPIC ASCENT REGIME ALONG SLY 50 KT
LLJ AXIS. WHILE MID-LEVEL LAPSE RATES ARE WEAKER THAN POINTS TO THE
W...AIR MASS IS STILL MODERATELY UNSTABLE FOR ELEVATED PARCELS WITH
MUCAPES OF AROUND 1000 J/KG. MOREOVER...FORECAST SOUNDINGS INDICATE
THAT CLOUD-BEARING SHEAR IS SUFFICIENTLY STRONG /I.E. EFFECTIVE BULK
SHEAR OF 40-50 KTS/ TO SUPPORT ORGANIZED/ROTATING UPDRAFTS CAPABLE
OF MAINLY LARGE HAIL.

..MEAD.. 05/21/2005

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

ATTN...WFO...MPX...FGF...ABR...BIS...UNR...

44940401 46890398 47109587 44959591 

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