Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000
FXUS65 KVEF 041656
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
956 AM PDT FRI SEP 4 2015

.SYNOPSIS...A STORM SYSTEM MOVING ACROSS THE PACIFIC NORTHWEST WILL
RESULT IN GUSTY SOUTH TO SOUTHWEST WINDS ACROSS THE AREA WITH THE
STRONGEST WINDS IN THE SOUTHERN GREAT BASIN. MOISTURE WILL ALSO
INCREASE ACROSS MOHAVE AND NORTHEAST CLARK COUNTIES ALLOWING FOR A
SHOWER OR THUNDERSTORM THIS AFTERNOON AND EVENING. THE STORM SYSTEM
WILL PASS ACROSS NEVADA ON SATURDAY RESULTING IN ANOTHER DAY OF
GUSTY WINDS. TEMPERATURES WILL REMAIN BELOW NORMAL THROUGH THE
WEEKEND THEN WARM BACK TO NEAR NORMAL BY THE MIDDLE OF NEXT WEEK.
DRY CONDITIONS ARE EXPECTED FOR NEXT WEEK.
&&

.UPDATE...

NO MAJOR CHANGES THIS MORNING, AS THE CURRENT FORECAST LOOKS IN
PRETTY GOOD SHAPE. DID, HOWEVER, INCREASE POPS TO SLIGHT CHANCE
ACROSS THE HIGHER TERRAIN OF EASTERN LINCOLN COUNTY. LOW-LEVEL
MOISTURE, INCLUDING SURFACE DEWPOINTS, HAVE INCREASED. THE SLIGHT
INCREASE IN MOISTURE COMBINED WITH THE UPPER-LEVEL DYNAMICS AND
INSTABILITY COULD SPARK A FEW ISOLATED SHOWERS/STORMS. SOME CUMULUS
DEVELOPMENT IS CURRENTLY ONGOING ACROSS THIS AREA AS WELL. WE SHALL
SEE IF ANYTHING CAN DEVELOP. ANY STORMS THAT DEVELOP WILL BE CAPABLE
OF GUSTY OUTFLOW WINDS GIVEN THE STRONG WINDS ALOFT MIXING DOWN AS
WELL AS STORM DEVELOPMENT BEING ON THE EDGE OF THE MOISTURE
BOUNDARY. IN OTHER NEWS, LATEST GUIDANCE INDICATES THE WIND AND FIRE
WEATHER HEADLINES LOOK GOOD TODAY AND TOMORROW, WITH NO CHANGES
ANTICIPATED AT THIS TIME.
&&

.PREVIOUS DISCUSSION...
327 AM PDT FRI SEP 4 2015

.SHORT TERM...TODAY THROUGH SUNDAY NIGHT.

FOR YET ANOTHER TIME THIS SUMMER, WE ARE DEALING WITH A RATHER
UNUSUAL SET-UP OF GUSTY WINDS AND HIGH FIRE DANGER IN SOME AREAS
WHILE OTHERS WILL BE DEALING WITH THE THREAT OF THUNDERSTORMS. A
TROUGH WAS WELL CARVED OUT ON WATER VAPOR IMAGERY THIS MORNING IN
THE MID AND UPPER LEVELS WITH AN ASSOCIATED AREA OF LOW PRESSURE
SPINNING OVER WESTERN WASHINGTON. THIS TROUGH IS EXPECTED TO DEEPEN
AS WE MOVE THROUGH THE DAY AS THE LOW HEADS TOWARD EASTERN OREGON.

A BELT OF STRONG WINDS ALOFT WILL ROUND THE BASE OF THE TROUGH AS A
60 KT+ JET AT 250 MB MOVES OVERHEAD. 700 MB WINDS ARE QUITE
IMPRESSIVE ACROSS MUCH OF THE AREA FOR THIS TIME OF THE YEAR SHOWING
WIDESPREAD 35 KT VALUES ON BOTH THE GFS AND ECMWF. THE WINDFIELDS AT
850 MB STILL ALIGN WELL ENOUGH TO ALLOW FOR THE HIGHER MOMENTUM
ALOFT TO GET MIXED DOWN TO THE SURFACE. THE ONE FACTOR GOING AGAINST
WINDS BEING MUCH HIGHER IS THE LACK OF A SUPER TIGHT SURFACE
PRESSURE GRADIENT. WINDS LOOK TO BE STRONGEST IN THE SOUTHERN GREAT
BASIN WHERE GUSTS OVER 40 MPH ARE EXPECTED AND THE WIND ADVISORIES
HERE ARE STILL JUSTIFIED. CROSS SECTIONS OF THE ARW AND NMM STILL
HINT THAT WE MAY SEE SOME WEAK DOWNSLOPE WINDS MATERIALIZE OFF THE
SOUTHERN SIERRA AND SPRING MOUNTAINS BUT VALUES ARE NOT HIGH ENOUGH
TO EXTEND HEADLINES INTO THESE AREAS. HOWEVER, IT WILL BE A VERY
WINDY START TO THE HOLIDAY WEEKEND IF YOU HAVE ANY OUTDOOR PLANS IN
THESE AREAS AT CAMPGROUNDS OR ON TRAILS. WINDS WILL DROP OFF THIS
EVENING AS THE BELT OF HIGHER WINDS ALOFT SHIFTS, SURFACE PRESSURE
GRADIENTS WEAKEN AND WE LOOSE THE HEATING THAT DRIVES THE THERMAL
COMPONENT THAT CAN ENHANCE WINDS.

WHILE A BONE DRY AIR MASS SITS OVER THE WESTERN HALF OF THE AREA,
PWATS HAVE COME UP IN AREAS NEAR AND EAST OF THE COLORADO RIVER
VALLEY. IPW SENSORS SHOW VALUES OF AROUND 0.75 INCH OR HIGHER FROM
VIDAL JUNCTION AND BULLHEAD CITY ON EAST. BY THIS AFTERNOON, BOTH
THE GFS AND WRF SHOW PWATS OF 0.75 INCH OR HIGHER AS FAR NORTH AS
THE MESQUITE AREA AND THE MOAPA VALLEY ANS PUSH THE 1 INCH LINE INTO
SOUTHERN MOHAVE COUNTY. WHILE THE GFS REMAINS THE WETTEST MODEL WITH
QPF, THE WRF REMAINS MUCH MORE UNSTABLE SHOWING LI`S AS HIGH AS -6
AND CAPE VALUES OVER 1000 J/KG IN MOHAVE COUNTY. WORTH NOTING IS A
70 KT+ JET STREAK AT 250 MB IS SHOWN TO MOHAVE NORTHEAST OVER
ARIZONA TODAY AHEAD OF THE MAIN TROUGH AXIS, WHICH WILL FURTHER AID
IN LIFTING OF THE AIR PARCELS. AS A RESULT, POPS WERE INCREASED
ACROSS ALL OF MOHAVE COUNTY AND ALSO A SLIGHT CHANCE OF
THUNDERSTORMS WAS ADDED INTO NORTHEAST CLARK COUNTY. FURTHER WEST,
IT STILL LOOKS TOO DRY AND STABLE. THE MAIN THREATS IN AND NEAR ANY
THUNDERSTORMS WILL BE GUSTY WINDS AND DOWNPOURS WHICH COULD RESULT
IN AT LEAST MINOR FLASH FLOODING.

HIGH TEMPS WERE BUMPED UP A FEW DEGREES TODAY GIVEN VALUES YESTERDAY
TOWARD THE WARMER END OF GUIDANCE, HOWEVER, ALL AREAS SHOULD STILL
DROP AT LEAST A DEGREE OR TWO FROM THURSDAY.

THE TROUGH IS EXPECTED TO WORK INTO NEVADA ON SATURDAY. THE GFS
REMAINS THE SLOWEST AT DRYING THE AREA OUT AND IN FACT NEVER REALLY
FLUSHES THE MOISTURE OUT OF MOHAVE COUNTY EVEN BY SUNDAY. THE OTHER
MODELS REMAIN MUCH DRIER. FOR NOW, WE WILL KEEP THE MENTION OF A
THUNDERSTORM IN AROUND THE MOUNT TRUMBULL AREA ON SATURDAY THEN KEEP
ALL AREAS DRY ON SUNDAY BEHIND THE TROUGH AXIS PASSAGE. WINDS WILL
REMAIN GUSTY ON SATURDAY AND WIND ADVISORIES REMAIN IN EFFECT FOR
NORTHEAST PARTS OF THE AREA. TEMPS WILL DROP A FEW MORE DEGREES FOR
SATURDAY THEN BE ABOUT STATUS QUO ON SUNDAY. WE CONTINUES TO LEAN
TOWARD THE WARMER END OF GUIDANCE. SUNDAY MORNING WILL FEEL
REFRESHING THOUGH NO MATTER HOW YOU LOOK AT IT WITH THE LOW IN LAS
VEGAS AT MCCARRAN AIRPORT DROPPING CLOSE TO 70.

.LONG TERM...MONDAY THROUGH THURSDAY.

THE DETAILS OF THE LONG TERM FORECAST REMAIN MURKY TONIGHT AS
POTENTIAL WILDCARD GETS THROWN INTO THE MIX. A NEW TROPICAL
DISTURBANCE IS CURRENTLY LOCATED NEAR 10N...105W IS FORECAST TO
STRENGTHEN OVER THE COURSE OF THE NEXT FIVE DAYS. OPERATIONAL MODEL
GUIDANCE CURRENTLY HANDLES THE EVOLUTION AND STRENGTH OF THIS SYSTEM
QUITE DIFFERENTLY AT THIS TIME. GIVEN THE FACT THAT WINDSHEAR IS
EXPECTED TO BECOME MORE FAVORABLE FOR DEVELOPMENT OVER THE
WEEKEND...THIS WILL BE SOMETHING TO KEEP CLOSE TABS ON NEXT WEEK AS
IT COULD HAVE AN IMPACT ON THE WEATHER ACROSS THE SOUTHWEST IF IT
CONTINUES TO TRACK NORTHWESTWARD.

ASIDE FROM THE NEW DEVELOPMENT IN THE TROPICS TONIGHT...THE LATEST
OPERATIONAL MODEL RUNS ARE GENERALLY IN LINE ON THE OVERALL PATTERN
THROUGH THE COMING WEEK. A RATHER BROAD OPEN WAVE IS EXPECTED TO
BRUSH ACROSS THE NORTHERN GREAT BASIN ON MONDAY...YIELDING BREEZY
SOUTHWESTERLY WINDS ACROSS OUR GREAT BASIN ZONES AND PORTIONS OF THE
MOJAVE DESERT. GENERAL BROAD TROUGHING ACROSS THE REGION WILL MOVE
OFF TO THE EAST BY MID-WEEK AS HIGH PRESSURE BEGINS TO BUILD IN OVER
THE WEST COAST BEHIND THE TROUGH. THE SUBTROPICAL HIGH WILL MIGRATE
WESTWARD ACROSS NORTHERN MEXICO THROUGH THE WEEK...OPENING THE DOOR
FOR TROPICAL MOISTURE TO POTENTIALLY SLOSH INTO AT LEAST SOUTHERN
PORTIONS OF THE FORECAST AREA BY MID WEEK. THIS FEATURE WILL
CONTINUE TO MOVE WESTWARD THROUGH LATE WEEK...HELPING TO AMPLIFY THE
RIDGING ACROSS THE WEST AND POTENTIALLY SETTING UP A NORTHWESTERLY
FLOW REGIME ACROSS THE FORECAST AREA BY FRIDAY. TEMPERATURES
WISE...EXPECT SEASONAL CONDITIONS THROUGH THE PERIOD. NO MAJOR
CHANGES IN WEATHER WERE MADE IN THE GRIDS TONIGHT...BUT THE
EVOLUTION OF THE AFOREMENTIONED TROPICAL WAVE WILL BE MONITORED
CLOSELY IN THE COMING DAYS AND SUBSEQUENT CHANGES WILL BE MADE AS
DETAILS BECOME CLEARER.
&&

.AVIATION...FOR MCCARRAN...WINDS WILL AGAIN INCREASE FROM THE SOUTH
TO SOUTHWEST BY 18Z AND BE STRONGEST LATE THIS AFTERNOON INTO THIS
EVENING WITH GUSTS OVER 25 KTS. WINDS WILL GRADUALLY DECREASE
BETWEEN 03Z AND 07Z THIS EVENING. ISOLATED SHRA AND TSRA ARE
POSSIBLE AFTER 18Z TODAY AND BEFORE 06Z SATURDAY IN THE PEACH
SPRINGS AND MORMON MESA APPROACH CORRIDORS WITH DRY CONDITIONS
ELSEWHERE.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...WINDS WILL AGAIN INCREASE FROM THE SOUTH TO SOUTHWEST
BY 18Z AND BE STRONGEST LATE THIS AFTERNOON INTO THIS EVENING WITH
GUSTS OF 25-35 KTS. MECHANICAL TURBULENCE IS POSSIBLE DUE TO
INCREASING WINDS WITH HEIGHT. WINDS WILL GRADUALLY DECREASE BETWEEN
03Z AND 07Z THIS EVENING. ISOLATED SHRA AND TSRA ARE POSSIBLE AFTER
18Z TODAY AND BEFORE 06Z SATURDAY EAST OF A KSGU-KIGM LINE WITH DRY
CONDITIONS ELSEWHERE.
&&

.FIRE WEATHER...CRITICAL FIRE WEATHER CONDITIONS EXPECTED ACROSS NYE
AND ESMERALDA COUNTIES ARE AGAIN EXPECTED TODAY DUE DRY FUELS, LOW
MINIMUM RELATIVE HUMIDITY VALUES AND WINDS OF 25-35 MPH WITH GUSTS
OF 40 TO 50 MPH. A RED FLAG WARNING REMAINS IN EFFECT THROUGH THIS
EVENING. ALTHOUGH GUSTY CONDITIONS ARE EXPECTED IN THE SPRING AND
SHEEP RANGE AND ACROSS LINCOLN COUNTY TODAY, MINIMUM RELATIVE
HUMIDITY VALUES MAY DIP BRIEFLY BELOW 15 PERCENT. VERY GUSTY WINDS
ARE EXPECTED ON SATURDAY ACROSS LINCOLN COUNTY, THE HIGHER TERRAIN
OF CLARK COUNTY AND THE NORTHWEST PLATEAU OF ARIZONA BUT RH VALUES
WILL ONLY BRIEFLY DIP BELOW 15 PERCENT.
&&

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

$$

UPDATE...PADDOCK
SHORT TERM/AVIATION/FIRE WEATHER...STACHELSKI
LONG TERM...PULLIN

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