MESO: Mesoscale Discussion 1349

ACUS11 KWNS 082142
SWOMCD
SPC MCD 082142
NEZ000-SDZ000-NDZ000-MTZ000-WYZ000-082345-

MESOSCALE DISCUSSION 1349
NWS STORM PREDICTION CENTER NORMAN OK
0442 PM CDT MON JUL 08 2013

AREAS AFFECTED...PORTIONS SERN MT...ERN WY...WRN SD...NEB PANHANDLE.

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 082142Z - 082345Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...WW LIKELY WILL BE REQUIRED OVER AT LEAST SERN PORTIONS MT
AHEAD OF SVR CONVECTION EXITING WW 398. MORE CONDITIONAL SVR
POTENTIAL EXTENDS SWD ACROSS ERN WY AND PORTIONS WRN SD/NEB
PANHANDLE. WW MAY INCLUDE SOME OF THOSE AREAS AS WELL.

DISCUSSION...CONVECTION NOW OVER CENTRAL MT IS EXPECTED TO EXIT WW
398 AROUND 2230Z...WHILE PROCEEDING INTO FAVORABLE AIR MASS. NARROW
CORRIDOR OF RELATIVELY MAXIMIZED BOUNDARY-LAYER THETAE EXTENDS NWWD
FROM SRN SD AROUND AREA OF STABILIZED AIR FROM EARLIER CLOUDS/PRECIP
OVER CENTRAL/WRN SD...INTO SERN/E-CENTRAL MT. THIS SUPPORTS
1500-2000 J/KG MLCAPE OVER ERN MT AND NERN WY. FARTHER S...WIDELY
SCATTERED CONVECTION HAS DEVELOPED OVER HIGHER TERRAIN OF ERN
WY...BUT APPEARS TO BE STRUGGLING WITH MASS CONTINUITY. BUOYANCY
AND LOW-LEVEL MOISTURE EACH INCREASE WITH EWD EXTENT FROM THAT
ACTIVITY...WITH SFC DEW POINTS 40S OVER MUCH OF ERN WY AND 50S OVER
NEB PANHANDLE W OF WW 400.

MODIFIED RAOBS AND MODEL SOUNDINGS EACH INDICATING MLCAPE 500-1000
J/KG NEAR WY/NEB BORDER AND INCREASING EWD. DEEP SHEAR DECREASES
WITH SWD EXTENT...WITH EFFECTIVE SHEAR MAGNITUDES GENERALLY 30-40 KT
OVER SERN MT AND FCST TO INCREASE WITH TIME AS NRN ROCKIES SHORTWAVE
TROUGH APCHS. MEANWHILE EFFECTIVE SHEAR MAGNITUDES SHOULD REMAIN IN
25-35 KT RANGE OVER ERN WY...SWRN SD AND WRN NEB. MOISTURE CHANNEL
IMAGERY SHOWS STG DRYING AND IMPLIED SUBSIDENCE ALOFT OVER ERN
WY/NEB PANHANDLE REGION...BEHIND SHORTWAVE TROUGH NOW CROSSING
S-CENTRAL SD AND N-CENTRAL NEB.

..EDWARDS/GOSS.. 07/08/2013

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

ATTN...WFO...BIS...LBF...UNR...CYS...BYZ...GGW...RIW...

LAT...LON 41130275 41380541 45150664 46640776 46720426 45850397
44500352 43540280 41610262 41130275

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