Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000
FXUS65 KVEF 300411
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
911 PM PDT TUE JUL 29 2014

.SYNOPSIS...LIMITED THUNDERSTORM DEVELOPMENT WILL BE CONFINED
PRIMARILY TO THE SOUTHERN SIERRA AND SOUTHERN GREAT BASIN UNDER A
DRIER AND MORE STABLE WEST TO SOUTHWEST FLOW ALOFT THROUGH FRIDAY.
ANOTHER PUSH OF MOISTURE IS EXPECTED TO SPREAD UP ACROSS THE REGION
OVER THE WEEKEND FOR AN UPSWING IN SHOWERS AND THUNDERSTORMS.
&&

.UPDATE...
OVERALL THE FORECAST IS ON TRACK TONIGHT...ONLY MADE A FEW MINOR
ADJUSTMENTS TO THE NEAR TERM FORECAST. WE HAVE BEEN WATCHING AN
OUTFLOW BOUNDARY MOVE INTO NORTHERN LINCOLN COUNTY FROM THE NORTH.
GUSTY NORTH WINDS OF 51 MPH WERE REPORTED AT KELY ABOUT 2 HOURS AGO.
THE BOUNDARY APPEARS TO BE WEAKENING AS IT SAGS SOUTH...WITH OTHER
OBSERVATIONS ONLY GUSTING IN THE 30-40 MPH RANGE. THIS BOUNDARY MAY
SPARK A FEW SHOWERS ACROSS LINCOLN COUNTY BUT NOT REALLY SEEING MUCH
LIGHTNING ANYMORE. CLOUD TOPS ARE NOT COOLING LIKE THEY WERE FARTHER
NORTH DURING A TIME OF GREATER INSTABILITY. WITHOUT ADDITIONAL
CONVECTION TO SUSTAIN MOMENTUM...EXPECT THIS BOUNDARY TO CONTINUE
WEAKENING WITH SOUTHWARD PROGRESSION. HIGH RES MODELS HAVE IT
WASHING OUT AROUND THE CLARK-LINCOLN COUNTY LINE OVERNIGHT.
&&

.PREVIOUS DISCUSSION...
320 PM PDT TUE JUL 29 2014

.SHORT TERM...THROUGH THURSDAY NIGHT...THUNDERSTORMS HAVE BEEN
SUBDUED TODAY AND LITTLE DEVELOPMENT IS EXPECTED THROUGH THE REST OF
THE AFTERNOON AND EVENING EXCEPT POSSIBLY OVER THE SOUTHERN SIERRA
AND SOUTH CENTRAL NEVADA. AN 18Z LAS VEGAS SOUNDING SHOWED A MARKED
INCREASE IN STABILITY WITH A NOTICEABLE CAP IN THE 650-500 MB LAYER
AND SLIGHTLY DRYING IN THE 700-500 MB LAYER. IN ADDITION...
INCREASING WEST TO NORTHWEST FLOW ON THE BACK SIDE OF THE THE BROAD
CIRCULATION LIFTING UP THROUGH UTAH HAS ACTED TO SHEAR CONVECTION
DEVELOPING OVER THE MOUNTAINS. THE PATTERN WILL NOT CHANGE MUCH
WEDNESDAY AND THURSDAY AS A DRY AND SOMEWHAT MODERATELY STABLE WEST
TO SOUTHWEST FLOW REMAINS OVER THE SOUTHERN HALF OF THE AREA.
SUFFICIENT MOISTURE AND INSTABILITY WILL REMAIN OVER THE SOUTHERN
SIERRA AND SOUTH CENTRAL NEVADA FOR A FEW THUNDERSTORMS TO DEVELOP
EACH AFTERNOON AND EVENING. ONE OTHER FEATURE TO WATCH IS
POST-TROPICAL CYCLONE HERNAN MOVING NORTHWARD HUNDREDS OF MILE WEST
OF THE BAJA SPUR. THE REMNANT MID AND HIGH LEVEL MOISTURE IS
FORECAST TO SPREAD ACROSS SOUTHERN CALIFORNIA AND THE SOUTHERN
SIERRA THROUGH WEDNESDAY NIGHT. THIS SHOULD LEAD TO A LITTLE
INJECTION OF MOISTURE TO FUEL SHOWERS OVER THE SIERRA WEDNESDAY. THE
REST OF THE REGION SHOULD JUST SEE ADDITIONAL MID TO HIGH LEVEL
CLOUDS.

.LONG TERM...FRIDAY THROUGH TUESDAY.

FRIDAY NOW LOOKS LIKE IT MAY BE THE LEAST ACTIVE DAY OF THE WEEK
ACROSS OUR AREA FOR SHOWERS AND THUNDERSTORMS AS THE FLOW ALOFT
REMAINS FROM THE SOUTHWEST AND DRIER AIR CONTINUES TO WORK EAST
ACROSS THE AREA. INSTABILITY REMAINS THE BEST ACROSS THE FAR
NORTHERN CWFA AND EASTERN MOHAVE COUNTY AND THAT IS WHERE WE
CONTINUED TO CONFINE A SLIGHT CHANCE FOR AFTERNOON AND EVENING
STORMS TO WITH HEATING AND TERRAIN DRIVING ACTIVITY ALONG WITH ANY
BOUNDARIES THAT FORM. OTHERWISE EXPECT NEAR SEASONABLE TEMPS WITH
DRY CONDITIONS.

JUST IN TIME FOR THE WEEKEND THINGS LOOK TO GET INTERESTING ONCE
AGAIN AS THE FOCUS TURNS TO AN INVERTED TROUGH OR SOME SORT OF
VORTICITY MAXIMUM OR LOBE FLOATING NORTHWEST AROUND THE RIDGE AXIS
ALOFT CENTERED NEAR THE FOUR CORNERS. THE 00Z OPERATIONAL RUNS OF
THE GFS, ECMWF AND GEM NOW SEEM TO BE SLOWER IN BRINGING THIS
FEATURE UP AND DELAY IT MORE UNTIL SATURDAY AFTERNOON INTO SATURDAY
NIGHT. HOWEVER, AN INFLUX OF MOISTURE IS PROGGED TO EJECT NORTH
FRIDAY NIGHT AND THIS SHOULD SET THIS STAGE FOR AN UPTICK IN SHOWER
AND THUNDERSTORM ACTIVITY ON SATURDAY, POSSIBLY STARTING IN THE
MORNING. AT THIS POINT, IT WOULD APPEAR THE EASTERN HALF OF THE AREA
WOULD BE THE MOST ACTIVE AS THE BETTER MOISTURE GETS INTO THESE
AREAS FIRST. THEN BY SATURDAY NIGHT INTO SUNDAY AS THE INVERTED
TROUGH OR VORTICITY MAXIMUM OR LOBE MOVES NORTH ACROSS OUR AREA
THINGS COULD GET EVEN MORE INTERESTING WITH THE POTENTIAL FOR
SHOWERS AND THUNDERSTORMS EVEN AT NIGHT AS THE PRESENCE OF THIS
FEATURE AS WELL AS BETTER 0-6 KM BULK SHEAR VALUES COULD ALSO
SUPPORT MORE ORGANIZED OR STRONGER CONVECTIVE ACTIVITY ON SUNDAY.
PWATS ARE PROGGED TO BE NEAR 1.50 INCH ACROSS THE SOUTHEAST CWFA
WHICH WILL MEAN THE ATMOSPHERE WILL HAVE PLENTY OF JUICE TO UNLOAD
HEAVY RAINFALL ALL WEEKEND IN STRONGER STORMS. THUS AN INCREASED
THREAT FOR FLASH FLOODING WILL EXIST. THE ONE THING IN THIS
SCENARIOS THAT IS A TOUGH CALL EVEN SHORTER IN TO THE EVENT IS HOW
MUCH CLOUD COVER WILL BE AROUND AS THIS WOULD LIMIT HEATING AND
COULD RESULT IN MORE OF A SHOWERS AND LOW GRADE THUNDERSTORM EVENT.
TEMPS SHOULD BE SEVERAL DEGREES BELOW NORMAL ALTHOUGH ANY GAIN IN
THE COMFORT FACTOR DEPARTMENT WILL BE OFFSET BY INCREASED HUMIDITY.

SUNDAY NIGHT INTO MONDAY, I WENT AHEAD AND BUMPED UP POPS SLIGHTLY
AS IT SEEMS MODELS ARE NOW SLOWER WITH DRYING ACROSS THE AREA IN THE
WAKE OF THE EJECTING FEATURE. DRIER AIR SHOULD CONTINUE TO SPREAD IN
FROM THE WEST ON TUESDAY. ACTIVITY THESE DAYS SHOULD BE MORE TERRAIN
AND BOUNDARY DRIVEN AND THUS I KEPT POPS GREATEST OVER THE HIGHER
TERRAIN ESPECIALLY IN THE NORTHERN AND EASTERN CWFA. TEMPS SHOULD
TREND CLOSER TO NORMAL AS SUNSHINE SHOULD BE MORE GENEROUS.
&&

.AVIATION...FOR MCCARRAN...PREVAILING SOUTHWEST WINDS AROUND 10
KNOTS WILL PERSIST OVERNIGHT THEN A LIGHT EASTERLY WIND COMPONENT
SHOULD DEVELOP LATE WEDNESDAY MORNING. SCT-BKN CLOUD BASES ABOVE 10
KFT CAN BE EXPECTED. ISOLATED THUNDERSTORMS WILL BE POSSIBLE IN THE
BEATTY AND MORMON MESA CORRIDORS WEDNESDAY AFTERNOON.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...AFTERNOON AND EVENING ISOLATED THUNDERSTORM DEVELOPMENT
WILL BE LIMITED TO THE SOUTHERN SIERRA...SOUTH CENTRAL NEVADA AND
NORTHWEST THROUGH WEDNESDAY. THE REST OF THE REGION WILL SEE WINDS
GENERALLY LESS THAN 15 KNOTS AND SCT-BKN MID TO HIGH LEVEL CLOUDS.
&&

.SPOTTER INFORMATION STATEMENT...SPOTTER ACTIVATION IS NOT EXPECTED
AT THIS TIME. HOWEVER...SPOTTERS ARE ENCOURAGED TO REPORT ANY
SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING
PROCEDURES.
&&

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

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