Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 290354
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
854 PM PDT TUE JUL 28 2015

.SYNOPSIS...HIGH PRESSURE EXPANDING WESTWARD WILL HELP DRAW MONSOON
MOISTURE BACK INTO THE REGION WEDNESDAY. THUNDERSTORM CHANCES ARE
EXPECTED TO OCCUR OVER MUCH OF THE SOUTHERN HALF OF THE FORECAST
AREA THROUGH THE END OF THE WEEK. TEMPERATURES WILL BE DEPENDENT OF
CLOUD COVER AND THUNDERSTORMS BUT SHOULD STAY CLOSE TO NORMAL.
&&

.UPDATE...A BATCH OF MID-LEVEL CLOUDS HAS DEVELOPED ACROSS SOUTHERN
MOHAVE, FAR SOUTHWEST SAN BERNARDINO AND LA PAZ COUNTIES THIS
EVENING AND WAS HEADING NORTHWEST. IN ADDITION...CLOUDS FROM ONGOING
CONVECTION FURTHER SOUTHEAST IN ARIZONA WERE ADVANCING TOWARD THE
NORTHWEST AS WELL TOWARD OUR SOUTHEAST CWFA. AS A RESULT I INCREASED
CLOUD COVER IN THESE AREAS FOR THE REST OF TONIGHT AND TOMORROW
MORNING. THE REST OF THE FORECAST LOOKS GOOD BUT AS IS THE CASE IN
THIS SORT OF PATTERN, AN EYE WILL NEED TO BE KEPT ON RADAR LATER
TONIGHT AS THERE IS ALWAYS THE SMALL POTENTIAL FOR SOMETHING TO
DRIFT ON IN.
&&

.AVIATION...FOR MCCARRAN...WINDS SHOULD TRANSITION TO A SOUTH-
SOUTHWEST DIRECTION OVERNIGHT AT 5-9 KTS. ON WEDNESDAY, WINDS WILL
FAVOR AN EASTERLY DIRECTION AND BE LESS THAN 8 KTS. SKIES WILL STAY
CLEAR TONIGHT WITH FEW-SCT CLOUDS ABOVE 12K FT DEVELOPING WEDNESDAY.

THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...TYPICAL DIURNAL WIND PATTERN EXPECTED AT ALL TERMINALS
TONIGHT AND WEDNESDAY. A SLIGHT CHANCE OF THUNDERSTORMS EXISTS
MAINLY OVER THE HIGHER TERRAIN OF THE MOJAVE DESERT WEDNESDAY. LOWER
CIGS AND GUSTY WINDS POSSIBLE NEAR STRONGER STORMS. OTHERWISE,
INCREASING CLOUDS ALONG AND SOUTH OF INTERSTATE 40 TONIGHT AND
WEDNESDAY. MOSTLY CLEAR SKIES ELSEWHERE.
&&

.PREVIOUS DISCUSSION...
ISSUED AT 220 PM PDT TUE JUL 28 2015

.SHORT TERM...THROUGH FRIDAY NIGHT.

LOW LEVEL MOISTURE REMAINS POOLED IN THE LOWER COLORADO RIVER VALLEY
WITH SURFACE DEWPOINTS IN THE MID 50S TO MID 60S FROM BLYTHE SOUTH
TO YUMA. NETWORK OF INTEGRATED PRECIPITABLE  WATER SENSORS IS
HIGHLIGHTING SIMILAR AREA WITH A SENSOR NEAR VIDAL JUNCTION CA UP TO
0.75 OF AN INCH WHILE YUMA IS GREATER THAN DOUBLE THAT AT 1.60
INCHES. SO FAR, STRONGEST CONVECTION IS FIRING OVER FAR SOUTHEAST
ARIZONA BUT DO EXPECT THIS ACTIVITY TO GO WELL INTO THE NIGHT ACROSS
SOUTHERN ARIZONA WITH A VERY SLIGHT CHANCE OF SHOWERS REACHING FAR
SOUTHERN MOHAVE AND FAR SOUTHEAST SAN BERNARDINO COUNTY WELL
AFTER MIDNIGHT.

ON WEDNESDAY...MOISTURE WILL ADVANCE FURTHER NORTHWARD WITH THE ONE
INCH PRECIPITABLE WATER LINE REACHING INTO FAR SOUTHERN CLARK
COUNTY. A TIGHT MOISTURE/INSTABILITY GRADIENT IN FORECAST ON A LINE
FROM NEAR BAKER-SEARCHLIGHT-KINGMAN. HIGH CONFIDENCE IN A SLIGHT
CHANCE OF SHOWERS AND THUNDERSTORMS IN SOUTHERN MOHAVE, SAN
BERNARDINO AND FAR SOUTHERN CLARK COUNTY. THERE IS AN UPPER LOW OVER
CENTRAL BAJA PENINSULA MOVING SLOWLY WESTWARD THAT COULD ACT AS A
TRIGGER FOR STORMS ALONG THE BAJA SPINE AND SAN DIEGO COUNTY
MOUNTAINS TOMORROW. SOUTHERN SAN BERNARDINO COUNTY MAY BE TOO FAR
NORTH FOR ANY INFLUENCE. THEREFORE, COUNTING ON SURFACE HEATING AS
THE TRIGGER WITH STORMS STAYING MAINLY ANCHORED TO THE HIGHER
TERRAIN.

FOR THURSDAY AND FRIDAY MADE LITTLE CHANGE TO THE EXISTING PACKAGE.
ONE INCH PRECIPITABLE WATER VALUES ARE FORECAST TO REMAIN PRIMARILY
OVER SAN BERNARDINO, SOUTHERN INYO AND NYE COUNTIES, CLARK AND
SOUTHERN TWO-THIRDS OF MOHAVE COUNTY. THERE REMAINS QUITE A BIT OF
UNCERTAINTY IN THE PLACEMENT/TIMING OF ANY FEATURES ROTATING AROUND
PERIPHERY OF HIGH THAT COULD HELP ORGANIZE STRONGER CONVECTION.
WITHOUT ANY DISTURBANCE CONVECTION WILL PRIMARILY BE TERRAIN
DRIVEN, BUT CAN NOT RULE OUT SOME STORMS REACHING THE VALLEYS.

NO SIGNIFICANT WINDS EXPECTED, EXCEPT THOSE ASSOCIATED WITH
THUNDERSTORMS WHILE THE INCREASE IN MOISTURE WILL KEEP TEMPERATURES
AT OR BELOW NORMAL.

.LONG TERM...SATURDAY THROUGH TUESDAY.

HIGH PRESSURE ALOFT WILL STAY CENTERED JUST TO OUR EAST THROUGH THE
WEEKEND. MOISTURE ALONG WITH SHOWER AND THUNDERSTORM CHANCES ARE
STILL EXPECTED TO SPREAD ACROSS THE ENTIRE MOJAVE DESERT AND
SOUTHERN GREAT BASIN. THE TERRAIN WILL HAVE THE BEST CHANCES OF
DEVELOPMENT, BUT CANNOT RULE OUT CONVECTION ROLLING INTO VALLEYS. DO
NOT SEE ANY SIGNIFICANT PV ANOMALIES THAT WOULD HELP ORGANIZE
CONVECTION ANY PARTICULAR DAY. SO, NOT EXPECTING WIDESPREAD SHOWERS
OR STORMS AT THIS TIME.

LATEST MODEL RUNS ARE BATTLING OVER WHETHER THE MOISTURE WILL LINGER
INTO MONDAY AND TUESDAY NEXT WEEK OR DRY OUT SOONER. THE ECMWF AND
TO A LESSER EXTENT THE GEFS AND NAEFS SUGGEST SLIGHT DRYING FROM THE
SOUTHWEST MONDAY AND PARTICULARLY TUESDAY, WITH MORE OF A SOUTHWEST
FLOW OVER PORTIONS OF THE REGION AS THE HIGH SHIFTS FARTHER SOUTH.
THE LATEST GFS KEEPS THE HIGH ANCHORED OVER THE FOUR-CORNERS REGION
AND THE MOISTURE LOCKED IN FOR OUR AREA. THIS IS IN CONTRAST WITH
IT`S ENSEMBLE MEMBERS. HOWEVER, THERE IS SPREAD AMONG THE ENSEMBLE
SOLUTIONS, RAISING UNCERTAINTY. MODELS OFTEN WANT TO SCOUR OUT THE
MOISTURE TOO SOON WHEN COMPARED TO WHAT ACTUALLY OCCURS. SO, WILL BE
CONSERVATIVE AND KEEP POPS LINGERING INTO MONDAY, WITH A DOWNWARD
TREND FOR TUESDAY.

WILL KEEP TEMPERATURES NEAR NORMAL VALUES THROUGH MUCH OF THE LONG
TERM PERIOD UNTIL WE CAN GET A HANDLE ON THE AMOUNT OF MOISTURE
INFLUX OVER THE WEEKEND AND JUST WHEN/IF THE DRYING TREND WILL BEGIN.
&&

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

$$

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

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