Flash Flood Warning 52, NWS Las Vegas, NV

MOJAVE DESERT/SOUTHERN GREAT BASIN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
250 PM PDT WED JUL 28 1999

SYNOPSIS...SOUTHERLY WINDS ALOFT WILL CONTINUE TO PROVIDE A FLOW OF
MOIST AND UNSTABLE AIR TO THE MOJAVE DESERT THROUGH FRIDAY. THIS WILL
HELP FUEL THE DEVELOPMENT OF SCATTERED THUNDERSTORMS EACH AFTERNOON
AND EVENING. A FLOW DRIER AND MORE STABLE AIR WILL PREVAIL OVER THE
REST OF THE SOUTHERN GREAT BASIN.

DISCUSSION...WITH EXTREMELY WEAK SHEAR AND LITTLE OR NO DYNAMICS...
STORMS HAVE FORMED FROM OROGRAPHICS AND HEATING THIS AFTERNOON.
DEVELOPMENT DELAYED OVER PARTS OF CLARK AND LINCOLN COUNTIES DUE TO
EARLIER CLOUD COVER BUT STILL EXPECTING CONVECTIVE TEMPERATURES TO BE
REACHED. FROM THIS POINT ON...STORMS TO BE DRIVEN BY OUTFLOW BOUNDARY
INTERACTION. AT 2130Z...ONE SUCH OUTFLOW BOUNDARY HEADING TOWARD LAS
VALLEY FROM AZ STORMS AND MAY YET AID DEVELOPMENT OVER LAS AND CLARK
COUNTY.

MODELS IN GOOD AGREEMENT ON KEEPING FORECAST AREA BETWEEN UPPER LOW
OFF CA COAST AND RIDGE TO THE EAST WITH SLY FLOW ALOFT. HOWEVER...
THEY OFFER LITTLE OR NO HELP IN THE DETAILS WITH EACH INDICATING
DIFFERENT AMOUNTS OF DRYING WITH TIME. GIVEN LITTLE CHANGE IN THE
UPPER FLOW CANNOT ACCEPT ANY SIGNIFICANT DRYING AND WILL GO WITH
PERSISTENCE FORECAST. FROM SATELLITE AND SURFACE OBSERVATIONS...
BELIEVE MONSOONAL MOISTURE BOUNDARY HAS PUSHED AS FAR WEST AS IT/S
GOING TO GO AND SHOULD REMAIN IN PLACE INTO FRI (MAINLY EAST OF A
TPH-DRA-DAG LINE). NO DYNAMICS OR FORCING TO FOCUS CONVECTION SO
OROGRAPHICS AND HEATING TO INITIATE STORMS EACH DAY.

THIS PATTERN PERSISTS INTO THE EXTENDED WITH LATEST MRF SHOWING ONLY
MINOR DIFFERENCES WITH PREVIOUS RUN. UPPER LOW REMAINS ANCHORED OFF
NRN CA COAST WITH EXTENSION OF ERN RIDGE CENTERED NEAR 4-CORNERS
REGION. SOUTH TO SOUTHEAST FLOW IN THE MID AND UPPER LEVELS TO KEEP
THE DOOR OPEN FOR PERIODIC SURGES OF DEEPER MOISTURE AND HELP STEER
ANY EASTERLY WAVES OUR WAY FOR CONTINUED AFT/EVE THUNDERSTORM
CHANCES.

NEMETH

.LAS...NONE.