SWOMCD
SPC MCD 261930
NEZ000-SDZ000-WYZ000-262130-
MESOSCALE DISCUSSION 1401
NWS STORM PREDICTION CENTER NORMAN OK
0230 PM CDT SUN JUN 26 2011
AREAS AFFECTED...PORTIONS CENTRAL/SRN SD...CENTRAL/NRN NEB...NEB
PANHANDLE...SERN WY.
CONCERNING...SEVERE THUNDERSTORM WATCH 557...
VALID 261930Z - 262130Z
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 557
CONTINUES.
NWRN NEB CONVECTION HAS EVOLVED INTO SVR AND EXPANDING MCS WITH TWO
EMBEDDED HEAVY-PRECIP SUPERCELLS...BASED ON WSR-88D PRODUCTS FROM
SRN SANDHILLS UNIT. DOMINANT MESOCIRCULATION MAY EMERGE FROM ONE OR
BOTH RELATED STORM-SCALE VORTICES...SUPPORTING POTENTIAL FOR
DEVELOPMENT OF BOW ECHO AND ACCELERATION OF COMPLEX ESEWD ACROSS NRN
NEB...AND IN TURN...ENHANCED DAMAGING WIND THREAT. MEANWHILE...THIS
ACTIVITY SHOULD CONTINUE ACROSS SANDHILLS WITH POTENTIAL FOR
LARGE/DAMAGING HAIL AND SVR GUSTS...AND A TORNADO OR TWO POSSIBLE AS
WELL. VWP AND RUC SOUNDINGS INDICATE FAVORABLE DEEP-LAYER SHEAR AND
STORM-RELATIVE INFLOW FOR SEVERAL MORE HOURS...WITH MOIST
ADVECTION/TRANSPORT INTO PROSPECTIVE INFLOW REGION LIKELY.
CURRENTLY...MLCINH DOES STRENGTHEN CONSIDERABLY WITH SEWD
EXTENT...BUT ALSO APPEARS TO BE ERODING NEARLY APACE WITH
TRANSLATION VECTOR OF MCS. IF PRESENT TRENDS CONTINUE OR
ACCELERATE...NEW WW MAY BE NEEDED FOR PORTIONS CENTRAL/NERN NEB
BEFORE 22Z.
FARTHER NW...DESPITE NWLY/POSTFRONTAL WINDS IN LOWEST LEVELS AND
RESULTANT DISPLACEMENT OF HODOGRAPH E AND SE OF ORIGIN...18Z UNR
RAOB SHOWED FAVORABLE BUOYANCY/SHEAR FOR SFC-BASED SUPERCELLS. RAOB
REVEALED 0-1 KM AGL SRH 150-200 J/KG DEPENDING ON STORM MOTION
USED...AND EFFECTIVE SHEAR MAGNITUDE 50-55 KT. THEREFORE...WRN
PORTIONS WW SHOULD BE MAINTAINED UNTIL AIR MASS BECOMES TOO STABLE
TO SUPPORT SVR THREAT WITH EXISTING OR LATER DEVELOPMENT MOVING OUT
OF BLACK HILLS/BADLANDS REGION. ONE UNCERTAINTY IS IN DURATION OF
THIS ACTIVITY...WHICH MAY ENCOUNTER OUTFLOW AIR ADVECTED NWD/NWWD
FROM NEB MCS.
ADDITIONAL DEVELOPMENT ALSO MAY OCCUR OVER HIGHER TERRAIN OF SERN WY
OR WRN/SRN PANHANDLE WHERE CINH IS DIMINISHING AND MOISTURE IS
FAVORABLE...THEN MOVE TOWARD SWRN PORTIONS WW. TO COVER SPATIAL
GAP...ADDITIONAL WW ACCORDINGLY MAY BE REQUIRED THIS AFTERNOON W OR
SW OF WW 557.
..EDWARDS.. 06/26/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...FSD...OAX...ABR...GID...LBF...UNR...CYS...
LAT...LON 41120360 41410459 42250469 43640324 44720125 44499885
42969814 42879738 42089746 41399856 41640066 41690187
41230268 41300261 41120360
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