Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000
FXUS65 KVEF 300347
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
847 PM PDT WED JUL 29 2015

.SYNOPSIS...MOISTURE WILL SPREAD FURTHER NORTH THURSDAY ALLOWING FOR
SHOWERS AND THUNDERSTORMS TO RETURN TO PARTS OF THE SOUTHERN GREAT
BASIN DURING THE AFTERNOON AND EVENING HOURS. THE CHANCE OF SHOWERS
AND THUNDERSTORMS WILL LINGER FROM FRIDAY INTO NEXT MONDAY THEN
BEGIN TO DECREASE IN MOST AREAS ON TUESDAY AND WEDNESDAY AS DRIER
AIR MOVES BACK IN. TEMPERATURES WILL REMAIN NEAR NORMAL THROUGH THE
WEEKEND WARMING TO SLIGHTLY ABOVE NORMAL EARLY NEXT WEEK.
&&

.UPDATE...WE CONTINUE TO SEE THE STRONGEST THUNDERSTORM ACTIVITY
THIS EVENING ACROSS CENTRAL SAN BERNARDINO COUNTY. THIS AREA REMAINS
ON THE EDGE BETWEEN DRIER AIR ALOFT AND MORE MOIST AIR TO THE
NORTHWEST WHICH IS LIKELY HELPING TO FUEL CONVECTION TO MORE
VIGOROUS LEVELS. FURTHER EAST, A BROADER AREA OF SHOWERS AND
THUNDERSTORMS WAS ADVANCING NORTHWEST ACROSS SOUTHERN MOHAVE AND
SOUTHEAST SAN BERNARDINO COUNTY. AS THIS MOVES NORTHWEST, THIS
SHOULD STABILIZE THINGS A BIT MORE AND RESULT IN LESS INTENSE
CONVECTION FOR THE REST OF THE NIGHT.

AN INVERTED TROUGH IN THE MID-LEVELS ALONG WITH ASSOCIATED VORTICITY
MAXIMUM IS SLATED TO MOVE NORTHWEST ACROSS SOCAL ON THURSDAY. THE
SOUTHEAST FLOW ALOFT WILL CONTINUE TO TRANSPORT RICHER MOISTURE
NORTHWARD WITH PWATS FORECASTED BY THE GFS TO BE OVER AN INCH ACROSS
ALL OF SAN BERNARDINO COUNTY AS WELL AS MUCH OF CLARK AND MOHAVE
COUNTIES AND FAR SOUTHERN INYO COUNTY. AFTER COORDINATION WITH WFO`S
OXNARD AND SAN DIEGO, WE HAVE GONE AHEAD AND ISSUED A FLASH FLOOD
WATCH FOR ALL OF INYO, MOST OF THE SAN BERNARDINO COUNTY DESERT
(EXCEPT THE COLORADO RIVER VALLEY) AS WELL AS SOUTHERN CLARK COUNTY
AND THE SPRING MOUNTAINS FOR THURSDAY. TO KEEP IT EASY THE WATCH
STARTS IN THE MID-MORNING BUT MOST AREAS WILL SEE ACTIVITY HOLD OFF
ON GETTING GOING UNTIL THE LATE MORNING OR EARLY AFTERNOON WITH THE
MAIN EXCEPTIONS BEING SAN BERNARDINO AND SOUTHERN INYO COUNTIES
WHERE THE ADDED FORCING OF THE TROUGH AND VORTICITY MAXIMUM MAY HELP
SET OFF THINGS EARLIER. RAINFALL TOTALS COULD EXCEED AN INCH OR TWO
EASILY IN A QUICK PERIOD IN THESE AREAS. POPS WERE ALSO BUMPED UP
SIGNIFICANTLY TO ACCOMPANY THE AREAS IN THE WATCH.
&&

.PREVIOUS UPDATE...
ISSUED AT 651 PM PDT WED JUL 29 2015

.UPDATE...THE SAN BERNARDINO COUNTY DESERTS REMAIN THE MOST ACTIVE
PART OF THE AREA AT THIS TIME AT SEVERAL SHORT-FUSED WARNINGS HAVE
BEEN ISSUED FOR THIS AREA. AS A RESULT, BASED ON THE LATEST RADAR
TRENDS, I INCREASED POPS FOR THE REST OF THIS EVENING FOR AREAS FROM
THE MOJAVE NATIONAL PRESERVE WEST TOWARD FORT IRWIN. SOUTHERN SAN
BERNARDINO COUNTY IS GETTING A BREAK IN MANY AREAS AS WATER VAPOR
SHOWS SOME DRIER AIR ALOFT WORKING ON IN, HOWEVER, THIS MAY HELP TO
TRIGGER CONVECTION ON THE DIFFERENTIAL MOISTURE BOUNDARY. ACROSS
SOUTHERN MOHAVE COUNTY, MAINLY LIGHT TO MODERATE RAIN SHOWERS WERE
MOVING NORTH, THOUGH THUNDER CANNOT BE DISCOUNTED HERE. POPS WERE
LEFT ALONE IN MOHAVE COUNTY. POPS WERE ALSO BUMPED UP A TAD IN
SOUTHERN INYO COUNTY MAINLY WEST OF SHOSHONE AS ACTIVITY FROM SAN
BERNARDINO COUNTY MAY DRIFT INTO THIS AREA AND THE LEADING PUSH OF
BETTER MOISTURE WAS ALSO HELPING TO TOUCH OFF SOME SHOWERS AND
THUNDERSTORMS.
&&

.PREVIOUS DISCUSSION...
ISSUED AT 240 PM PDT WED JUL 29 2015

.SHORT TERM...THROUGH SATURDAY NIGHT.

FRIDAY AND SATURDAY. THE WEAK UPPER LOW NEAR SOUTHERN BAJA WILL
FINALLY OPEN UP AND MOVE NORTHWARD ACROSS THE SOUTHERN CALIFORNIA
FRIDAY/FRIDAY NIGHT WHICH AGAIN COULD HELP FOCUS CONVECTION OVER THE
HIGHER TERRAIN OF SOUTHERN CALIFORNIA. MODELS STARTING TO SHOW A
DRIER AND MORE STABLE AIR MASS MOVING IN BEHIND THIS FEATURE
SATURDAY. DID NOT DECREASE POPS WITH THIS PACKAGE BUT IF THAT TREND
CONTINUES WE COULD START LOWERING POPS IN THE WESTERN AREAS.

.LONG TERM...SUNDAY THROUGH WEDNESDAY.

IT IS LOOKING LIKE A LOW GRADE MONSOON PATTERN FOR THIS PERIOD. HIGH
PRESSURE CENTERED NEAR THE FOUR CORNERS REGION SUNDAY WILL KEEP A
SOUTHERLY FLOW OVER THE AREA AND ENOUGH MOISTURE AND INSTABILITY FOR
AT LEAST A SLIGHT CHANCE OF THUNDERSTORMS AREA WIDE. THE MODELS DO
NOT REALLY SHOW MUCH OF A SHIFT IN THE HIGH CENTER WITH TIME BUT
THEY ARE HINTING AT THE FLOW MAYBE BECOMING MORE SOUTHWESTERLY WITH
SOME DRYING ACROSS THE WESTERN PART OF THE FORECAST AREA WITH TIME.
SINCE THE GFS AND ECMWF ARE BOTH SHOWING THIS TREND I WENT AHEAD AND
LOWERED POPS A TOUCH IN THE WEST SUNDAY AND MONDAY AND LOWERED POPS
A BIT MORE FOR TUESDAY AND WEDNESDAY. IF YOU BELIEVE THE MODELS
THERE MAY NOT BE ANY THUNDERSTORMS IN THE CWA BY TUESDAY BUT AS WE
HAVE MENTIONED BEFORE...THE MODELS FREQUENTLY GET TOO AGGRESSIVE
FLUSHING MOISTURE OUT THIS TIME OF YEAR. SO I KEPT A SLIGHT CHANCE
OF THUNDERSTORMS THROUGH WEDNESDAY FOR MAINLY MOHAVE AND LINCOLN
COUNTIES AND THE HIGHER TERRAIN OF CLARK COUNTY. I KEPT TEMPERATURES
CLOSE TO OR JUST SLIGHTLY ABOVE NORMAL FOR THE LONG TERM WHICH IS
CLOSE TO THE GFS MEX GUIDANCE. I AM NOT READY TO BUY THE SIGNIFICANT
WARMING INDICATED BY THE ECE GUIDANCE WHICH HAS TEMPERATURES 5 PLUS
DEGREES ABOVE NORMAL SUNDAY THROUGH TUESDAY.
&&

.AVIATION...FOR MCCARRAN...THUNDERSTORMS WILL STAY SOUTH OF LAS
VEGAS BUT MAY AFFECT THE DAGGETT APPROACH CORRIDORS. CONFIDENCE LOW
IN OUTFLOW WIND FROM THOSE STORMS AFFECTING LAS VEGAS TERMINALS BUT
IT DOES BEAR MONITORING. EASTERLY COMPONENT WILL TRANSITION
SOUTHERLY OVERNIGHT WITH SPEEDS LESS THAN 10 KTS. THERE IS A CHANCE
OF THUNDERSTORMS THURSDAY OVER THE MOUNTAINS MOSTLY WEST AND SOUTH
OF LAS VEGAS. BEATTY, DAGGETT AND PEACH SPRINGS CORRIDORS WILL BE
IMPACTED BY THUNDERSTORMS. ANY OUTFLOW FROM STORMS WILL BE CLOSELY
MONITORED.

THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...A CHANCE OF SHOWERS AND THUNDERSTORMS EXISTS MAINLY
OVER THE HIGHER TERRAIN IN AREAS SOUTH OF A KNID-KIGM LINE WITH SCT-
BKN CLOUDS AVERAGING AOA 10-12K FEET TONIGHT. LOWER CIGS AND GUSTY
WINDS POSSIBLE NEAR STRONGER STORMS. MOSTLY CLEAR NORTH OF A KNID-
KIGM LINE. ON THURSDAY THE CHANCE OF THUNDERSTORMS MAINLY OVER THE
HIGHER TERRAIN SPREAD FURTHER NORTH INTO INYO COUNTY AND SOUTHERN
NEVADA.
&&

.SPOTTER INFORMATION STATEMENT...SPOTTERS ARE ENCOURAGED TO REPORT
ANY SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING
PROCEDURES.
&&

$$

UPDATE...STACHELSKI
SHORT TERM/AVIATION...PIERCE
LONG TERM...HARRISON

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