SWODY1
SPC AC 271959
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT FRI AUG 27 2010
VALID 272000Z - 281200Z
...NO SVR TSTM AREAS FORECAST...
...SWRN U.S...
AT 1930Z...WAVER VAPOR IMAGERY AND RADAR INDICATED A SEWD MOVING MCV
WAS LOCATED ABOUT 50 NM S OF PHX...WHILE ANOTHER IMPULSE WAS MOVING
NEWD THROUGH NRN UT. BOTH FEATURES SHOULD ENHANCE THUNDERSTORM
COVERAGE THIS AFTERNOON WITHIN MOIST TROPICAL PLUME. CURRENT
FORECAST APPEARS ON TRACK WITH REGARD TO LOW END SEVERE WEATHER
THREATS IN AZ...WHERE RICHER BOUNDARY LAYER MOISTURE FROM BAJA IS
RESULTING IN STRONGER INSTABILITY...AS WELL AS A LOW END THREAT
ACROSS PORTIONS OF UT/WY DUE TO STRENGTHENING WINDS ALOFT/ VERTICAL
SHEAR. HOWEVER...OVERALL COVERAGE OF STRONG TO SEVERE STORMS IS
EXPECTED TO BE SMALL...SO 5% WIND PROBABILITIES WERE MAINTAINED.
...ERN NC...
SMALL CLUSTER OF MULTICELL STORMS HAD DEVELOPED IN THE PAST HOUR OR
SO NEAR THE NERN NC/SERN VA BORDER. GIVEN MLCAPES AROUND 1500 J/KG
AND 30-35 KT OF DEEP LAYER SHEAR...A FEW OF THESE STORMS MAY PRODUCE
MARGINALLY SEVERE HAIL AS THEY MOVE SSEWD THROUGH THE AFTERNOON
HOURS.
...SERN STATES....
LATEST SURFACE ANALYSIS INDICATED A 1010 MB SURFACE LOW PRESSURE WAS
CENTERED ABOUT 125 MI SW OF MSY...WITH SURFACE TROUGH EXTENDING NEWD
INTO THE ERN AL. ON THE ERN SIDE OF THIS SYSTEM... DEEP SLY WINDS
ARE ADVECTING A VERY MOIST AIR MASS NWD...WITH GPS SATELLITE ALREADY
INDICATING PW VALUES NEAR 2 INCHES INLAND ABOUT 100 NM. THOUGH
MUCAPES BETWEEN 2000 TO 3000 J/KG ARE EVIDENT ACROSS THE
REGION...WEAK LAPSE RATES AND SLOW WWD MOTION OF STORMS SUGGEST
LOCALLY HEAVY RAINS WILL BE THE GREATEST THREAT.
..IMY.. 08/27/2010
.PREV DISCUSSION... /ISSUED 1112 AM CDT FRI AUG 27 2010/
...SWRN U.S...
LARGE SCALE PATTERN CHANGE WELL UNDERWAY AS TROUGH DEVELOPS WRN U.S.
AND HEIGHTS RISE IN THE EAST. THE STRONG SYSTEM MOVING THRU
ALBERTA/SASKATCHEWAN WILL PUSH A COLD FRONT EWD ACROSS NRN PLAINS
THRU THE PERIOD. THE FRONT TRAILS BACK INTO NRN UT/NV BY LATER THIS
AFTERNOON WHERE IT STALLS AS TROUGH DEEPENS SEWD ALONG W COAST.
MONSOONAL PLUME OF MOISTURE EXTENDS NWD FROM AZ THRU UT AHEAD OF
FRONTAL ZONE THIS AM AND WILL PERSIST IN THIS AREA THRU THE PERIOD
AS MID LEVEL WINDS INCREASE/BACK ACROSS NV/UT BY TONIGHT IN RESPONSE
TO DEEPENING W COAST TROUGH.
A WEAK UPPER TROUGH CURRENTLY DRIFTING EWD ACROSS AZ WILL CONTINUE
TO SUPPORT ACTIVE THUNDERSTORMS THIS AFTERNOON/EVENING. BOTH TUS/PHX
SOUNDINGS QUITE MOIST WITH THE CURRENT CONVECTION CENTRAL AZ
PERSISTING AND LIKELY INTENSIFYING ACROSS THE SERN THIRD OF AZ WHERE
AIR MASS BECOMES MDTLY UNSTABLE WITH MLCAPES CLIMBING ABOVE 2000
J/KG AS VALLEY TEMPS WARM THRU THE 80S. WHILE SHEAR IS
WEAK...CLUSTERS OF STRONG STORMS WILL SUPPORT BRIEF DAMAGING WINDS
THRU THE AFTERNOON.
FURTHER N ACROSS UT INTO SWRN WY...WHILE MOISTURE IS LESS...LAPSE
RATES ARE STEEPER AND SHEAR IS STRONGER. GUSTY WINDS WILL BE
ASSOCIATED WITH THE STRONGER STORMS THAT DEVELOP WITHIN MONSOONAL
PLUME WITH POSSIBLY ISOLATED DAMAGING GUSTS...PARTICULARLY ACROSS
NRN UT INTO SWRN WY WHERE SHEAR IS GREATER.
LARGE SCALE ASCENT AND SHEAR DOES INCREASE AFTER 00Z AS THE TROUGH
DEEPENS TO THE W...WHICH COULD LEAD TO MORE WIDESPREAD CONVECTION
ACROSS NRN UT/SWRN WY. HOWEVER LACK OF INSTABILITY SHOULD PRECLUDE
AN ORGANIZED SEVERE THREAT.
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