Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 290956
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
256 AM PDT WED JUL 29 2015

.SYNOPSIS...MOISTURE WILL SPREAD NORTH INTO THE AREA TODAY INTO
TOMORROW ALLOWING FOR SHOWERS AND THUNDERSTORMS TO RETURN TO SOME
AREAS MAINLY 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 AS DRIER AIR MOVES
BACK ON IN. TEMPERATURES WILL REMAIN NEAR NORMAL THROUGH THE WEEKEND
WARMING TO SLIGHTLY ABOVE NORMAL EARLY NEXT WEEK.
&&

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT.

AS IS EVIDENT ON SATELLITE AND LOOKING AT OBSERVATIONS THIS MORNING
MOISTURE IS MAKING A MOVE ON NORTH. IPW SENSORS SHOW A STEADY CLIMB
IN PWAT VALUES SINCE YESTERDAY WITH VALUES MAINLY BETWEEN 0.50 INCH
AND 1.00 INCH ACROSS MUCH OF THE AREA AND AS HIGH AS 1.48 INCH AT
VIDAL JUNCTION. SURFACE DEWPOINTS HAVE SHOWN A STEADY RISE IN THE
COLORADO RIVER VALLEY AS WELL IN THIS TIME FRAME. THERE WAS AN AREA
OF CLOUDS THAT POPPED UP LATE YESTERDAY EVENING IN LA PAZ AND
SOUTHERN MOHAVE COUNTIES WHICH HAS MOVED NORTH OVERNIGHT AND EVEN
TRIGGERED SOME RETURNS ON RADAR THIS MORNING. AS A RESULT, POPS WERE
TWEAKED UP A BIT TO ACCOUNT FOR THE POTENTIAL OF A FEW SPRINKLES OR
A VERY LIGHT SHOWER REACHING THE GROUND IN SOUTHERN MOHAVE AND
SOUTHEAST SAN BERNARDINO COUNTIES.

THE FLOW ALOFT REMAINS SOUTH TO SOUTHEAST INTO TONIGHT WHICH WILL
CONTINUE TO TRANSPORT MOISTURE ON UP. PWATS WILL CONTINUE TO RISE
THROUGH THE DAY AND BE OVER AN INCH ACROSS MOST OF THE SAN
BERNARDINO COUNTY DESERTS, SOUTHERN CLARK AND CENTRAL AND SOUTHERN
MOHAVE COUNTIES. WHILE WE WILL HAVE THE MOISTURE GOING FOR US TODAY
AS WELL AS SUFFICIENT INSTABILITY AND CAPE VALUES (LI`S OF 0 TO -2
COMPUTED AT THE SURFACE AND CAPE VALUES OF 300-600 J/KG), THERE IS
REALLY NO REAL MECHANISM OTHER THAN TERRAIN AND HEATING TO DRIVE
STORMS. THE MID AND HIGHER LEVEL CLOUD COVER STREAMING NORTH THIS
MORNING IS NOT TOO THICK AT THE PRESENT BUT COULD BE ENOUGH TO TRIM
BACK ON ACTIVITY IN MOHAVE COUNTY OR DELAY THE START OF IT. NORTH OF
THIS AREA, IT WILL BE TOO DRY AND TOO STABLE TODAY TO SEE MUCH
ACTIVITY THOUGH WE MAY SEE SOME CUMULUS DEVELOP THIS AFTERNOON
ESPECIALLY OVER THE SOUTHERN SIERRA. HIGH TEMPS WERE TWEAKED UP A
FEW DEGREES BASED ON YESTERDAY`S HIGHS AS WELL AS A BLEND OF THE
LATEST STATISTICAL GUIDANCE.

ACTIVITY SHOULD DECREASE THIS EVENING WITH THE LOSS OF HEATING.
THERE IS SOME POTENTIAL THURSDAY THAT SOME SORT OF MID-LEVEL
WEAKNESS AND ASSOCIATED PV MAX HEADS NORTHWEST, HOWEVER, THIS MAY
ALSO DEPEND ON WHAT GOES ON TO OUR SOUTHEAST THIS EVENING OVER THE
CENTRAL AND SOUTHERN PARTS OF ARIZONA. OTHERWISE MOISTURE WILL
LINGER AND SPREAD FURTHER NORTH ON THURSDAY AND BE SUFFICIENT FOR
SHOWERS AND STORMS IN ANY PART OF THE AREA BY FRIDAY. AGAIN, HEATING
AND TERRAIN WILL MAINLY DRIVE STORMS. TEMPS WILL REMAIN NEAR NORMAL
FOR HIGHS.

THE MAIN THREATS IN AND NEAR STORMS WILL BE GUSTY WINDS, HAIL,
BLOWING DUST AND FLASH FLOODING IN ANY STRONGER OR SLOWER MOVING
STORMS. THE FLASH FLOOD THREAT WILL INCREASE A BIT MORE THURSDAY
INTO FRIDAY AS THE MOISTURE CONTENT OF THE AIR INCREASES.

.LONG TERM...SATURDAY THROUGH TUESDAY.

IT IS LOOKING LIKE A LOW GRADE MONSOON PATTERN FOR THIS PERIOD. HIGH
PRESSURE CENTERED NEAR THE FOUR CORNERS REGION SATURDAY 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. 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 IN
TUESDAY 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...WINDS WILL FAVOR AN EASTERLY DIRECTION
AND BE LESS THAN 8 KTS THROUGH 03Z OR SO THURSDAY THEN TRANSITION TO
THE SOUTHWEST. FEW-SCT CLOUDS ABOVE 12K FT THIS AFTERNOON INTO
TONIGHT. THERE IS A SLIGHT CHANCE OF A SHRA OR TSRA AFTER 20Z TODAY
IN THE DAGGETT AND PEACH SPRINGS APPROACH CORRIDORS THROUGH AROUND
04Z OR SO THURSDAY.

THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...TYPICAL DIURNAL WINDS ARE EXPECTED THROUGH TONIGHT AT
ALL TERMINALS. A SLIGHT CHANCE OF THUNDERSTORMS EXISTS MAINLY OVER
THE HIGHER TERRAIN IN AREAS SOUTH OF A KDAG-KIGM LINE WITH SCT-BKN
CLOUDS AVERAGING AOA 7-12K FEET. LOWER CIGS AND GUSTY WINDS POSSIBLE
NEAR STRONGER STORMS. MOSTLY CLEAR NORTH OF A KDAG-KIGM LINE.
&&

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

$$

SHORT TERM/AVAITION...STACHELSKI
LONG TERM...HARRISON

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