Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 300927
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
227 AM PDT THU OCT 30 2014

.SYNOPSIS...A DISTURBANCE WILL PASS ACROSS THE AREA TODAY BRINGING
CONSIDERABLE HIGH CLOUDS WITH IT. OTHERWISE EXPECT WARM WEATHER
THROUGH HALLOWEEN BEFORE A STORM SYSTEM MOVES ON IN USHERING IN
GUSTY WINDS AND MUCH COOLER TEMPERATURES ALONG WITH POSSIBLE RAIN
AND MOUNTAIN SNOW SHOWERS HALLOWEEN NIGHT THROUGH SUNDAY. DRY
CONDITIONS WITH A SLOW WARMING TREND ARE EXPECTED MONDAY THROUGH THE
MIDDLE OF NEXT WEEK.
&&

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT.

WE ENJOYED YET ANOTHER MILD DAY YESTERDAY ACROSS THE AREA AND ONCE
AGAIN TODAY WILL BE ABOVE AVERAGE ACROSS THE AREA. THE ONLY
DIFFERENCE WILL BE HOW MUCH SUNSHINE IS AROUND AS HIGH CLOUDS WILL
BE RATHER PLENTIFUL AT TIMES. A MID/UPPER LEVEL LOW CURRENTLY NOTED
ON WATER VAPOR IN THE PACIFIC NEAR 30N/125W WILL CONTINUE TO MOVE
NORTHEAST TODAY AND ACROSS OUR AREA THIS AFTERNOON AND EVENING. THIS
WILL SPREAD A DECENT SHIELD OF CIRRUS IN BY LATE THIS MORNING THAT
WILL TAKE UNTIL THIS EVENING OR EARLY TONIGHT TO DEPART. HOWEVER,
FORECAST SOUNDINGS SHOW FURTHER WARMING TODAY AND CROSS SECTIONS
KEEP MOST OF THE MOISTURE IN A SMALL LAYER AROUND 300 MB, SO HIGHS
SHOULD STILL TREND UP A FEW DEGREES TODAY FROM WHAT WE SAW ON
WEDNESDAY.

THE LATEST OPERATIONAL MODELS LOOK A LITTLE SLOWER AT BRINGING THE
FIRST NOTEWORTHY FALL STORM INTO OUR AREA. A MID/UPPER TROUGH IS
EXPECTED TO APPROACH CALIFORNIA TOMORROW AND MOVE ACROSS NEVADA ON
SATURDAY MORNING. HALLOWEEN SHOULD STAY DRY FOR MOST OF THE AREA
EXCEPT FAR WESTERN PORTIONS WITH CIRRUS PUSHING BACK ON IN AND WINDS
PICKING UP FROM THE SOUTH IN THE AFTERNOON AND EVENING. FORECAST
SOUNDINGS SHOW SOME COOLING, HOWEVER, MOST STATISTICAL GUIDANCE AND
BIAS CORRECTED GUIDANCE SHOWS TEMPS WARMING UP A FEW MORE DEGREES
AND GIVEN THE BETTER LOW-LEVEL MIXING I HAVE KEPT TEMPS CLOSE TO
WHAT WE HAVE BEEN FORECASTING. MODELS CONTINUE TO SHOW A LACK OF
ALIGNMENT OF THE WINDFIELDS BELOW 700 MB WITH THE STRONGER WINDS
ABOVE THAT LEVEL, WHICH WILL HELP TO CUT DOWN ON THE STRENGTH OF THE
WINDS IN MOST AREAS FOR HALLOWEEN NIGHT. THUS GUSTS OF 25-35 MPH
SHOULD BE IT. THE EXCEPTION WILL BE ACROSS THE RIDGETOPS OF THE
SOUTHERN SIERRA, WHITE MOUNTAINS AND THE SPRING MOUNTAINS WHERE
GUSTS OVER 40 MPH COULD OCCUR. HOWEVER, THE LACK OF CROSS BARRIER
FLOW WILL PREVENT ANY DOWNSLOPE WIND THREAT FOR THE OWENS VALLEY IN
THE EVENING OR NIGHT HOURS ON HALLOWEEN.

PRECIPITATION SHOULD START TO SPREAD INTO THE AREA FRIDAY EVENING AS
PVA INCREASES AHEAD OF THE BASE OF THE MID/UPPER LEVEL TROUGH MOVING
INTO CALIFORNIA. WHILE THE MOISTURE TAP IS NOT IMPRESSIVE WITH THIS
STORM, JUST ENOUGH MOISTURE COMBINED WITH SUFFICIENT FORCING SHOULD
SPREAD PRECIPITATION OVER THE SOUTHERN SIERRA TO JUSTIFY LIKELY TO
CATEGORICAL POPS ACROSS INYO AND ESMERALDA COUNTIES. 700 MB TEMPS
OFF THE GFS AND ECMWF DROP TO -4C, WHICH STILL SUPPORTS SNOW LEVELS
DOWN TO AROUND 6000 FEET. SPILLOVER INTO THE EASTERN SLOPES OF THE
SOUTHERN SIERRA NEVADA LOOKS GOOD AND THE WINTER STORM WATCH HERE
STILL IS JUSTIFIED WITH THE HIGHEST AMOUNTS NEAR THE CREST WHERE
TOTALS WILL EASILY EXCEED 6 INCHES. HIKERS AND CAMPERS SHOULD BE
WARE OF THE SNOW, WIND AND COLDER TEMPERATURES. IN THE WHITE
MOUNTAINS AND ON SATURDAY MORNING IN THE SPRING MOUNTAINS, 1 TO 3
INCHES OF SNOW ARE POSSIBLE ABOVE 7000 FEET. MOST OF THE
PRECIPITATION SHOULD FALL IN A SHORT SPAN OF SEVERAL HOURS AHEAD OF
AND WITH THE BASE OF THE 500 MB TROUGH. PWATS JUST ABOVE 0.50 INCH
ARE SHOWN TO WORK INTO THE MOJAVE DESERT, AND ALTHOUGH SOUNDINGS ARE
NOT OVERLY IMPRESSIVE, SOME LIGHT RAIN IS POSSIBLE IN AREAS AS FAR
SOUTH AS BARSTOW, PAHRUMP AND KINGMAN. IN THE LAS VEGAS VALLEY, A
FEW SPRINKLES OR A QUICK RAIN SHOWER IS POSSIBLE, MAINLY ON THE
WEST SIDE.

ONCE THE TROUGH AXIS MOVES THROUGH, SOMEWHAT DRIER AIR SHOULD WORK
ON IN FOR THE REST OF SATURDAY, WHICH WILL END THE CHANCE FOR
SHOWERS IN THE LOWER MOJAVE DESERT ELEVATIONS. HOWEVER, LINGERING
ENERGY ROTATING THROUGH THE TROUGH AND JUST ENOUGH MID-LEVEL
MOISTURE WILL STILL HOLD ON IN THE SOUTHERN GREAT BASIN TO JUSTIFY
KEEPING THE POTENTIAL FOR SHOWERS AROUND THROUGH SATURDAY NIGHT.
HIGHS ON SATURDAY SHOULD BE ABOUT 15 DEGREES COLDER THAN WHAT WE SEE
ON HALLOWEEN. FOR MANY VALLEY LOCATIONS IN THE SOUTHERN GREAT BASIN
THAT HAVE YET TO SEE A FREEZE, THE GROWING SEASON WILL COME TO AN
END ON SUNDAY MORNING.

.LONG TERM...SUNDAY THROUGH WEDNESDAY...

YESTERDAYS 12Z SUITE OF MODELS CHANGED THEIR TUNE INDICATING
ADDITIONAL SHORTWAVE ENERGY AFFECTING THE SOUTHERN GREAT BASIN AND
MOJAVE DESERT SUNDAY. THE 00Z SUITE OF MODELS CONTINUED WITH SIMILAR
IDEA SO HAVE KEPT IN A SLIGHT CHANCE OF SHOWERS FOR THE HIGHER
TERRAIN INTO SUNDAY. ALL MODELS SHOW A TROUGH HANGING BACK OVER
ARIZONA MONDAY WITH ANY PRECIPITATION CHANCES OCCURRING EAST OF
MOHAVE COUNTY. ON TUESDAY/WEDNESDAY...THERE ARE SOME DIFFERENCES IN
JUST HOW FAST THE TROUGH WEAKENS AND SHIFTS EAST THOSE DAYS.
HOWEVER...IT SHOULD NOT HAVE ANY AFFECT ON CALIFORNIA/NEVADA AS
AS A RIDGE OF HIGH PRESSURE STARTS BUILDING IN FROM THE WEST. MAIN
PUSH OF SOME GUSTY NORTH WINDS LOOKS TO OCCUR SUNDAY NIGHT INTO
MONDAY MORNING. THOSE NORTH WINDS WILL STAY MOSTLY CONFINED WITHIN
THE COLORADO RIVER VALLEY MONDAY-WEDNESDAY...WHILE AWAY FROM THE
COLORADO RIVER VALLEY NORTH WINDS WILL SUBSIDE EACH DAY.
TEMPERATURES WILL BE AT THEIR COOLEST SUNDAY THEN WARM EACH DAY
THROUGH WEDNESDAY.
&&

.AVIATION...FOR MCCARRAN...WINDS SHOULD MAINLY BE 8 KTS OR LESS AND
FAVOR TYPICAL DIURNAL DIRECTIONAL TRENDS THROUGH TONIGHT. SCT-BKN
CLOUDS AOA 25K FEET. A STORM SYSTEM WILL APPROACH THE AREA FRIDAY
RESULTING IN GUSTY WINDS OVER 20 KTS FRIDAY EVENING INTO EARLY
SATURDAY EVENING. AS THE STORM MOVES ACROSS THE AREA ON SATURDAY
THERE WILL BE THE POTENTIAL FOR CLOUD BASES AS LOW AS 7K-10K FEET AS
WELL AS FEW SHRA IN AND AROUND THE LAS VEGAS VALLEY MAINLY IN THE
MORNING HOURS.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...VFR CONDITIONS WITH WINDS 10 KTS OR LESS FAVORING
TYPICAL DIURNAL TRENDS ARE EXPECTED THROUGH FRIDAY MORNING. GUSTY
WINDS OVER 20 KTS ARE EXPECTED FRIDAY AFTERNOON INTO SATURDAY AS A
STORM SYSTEM PASSES ACROSS THE AREA. CLOUD BASES AS LOW AS 5K-10K
FEET ALONG WITH POSSIBLE SHOWERS CAN BE EXPECTED ESPECIALLY NORTH OF
KDAG-KLAS-KIGM LINE WITH THE GREATEST CHANCES IN AND AROUND KBIH.
VSBY IN VALLEYS MAY BRIEFLY LOWER TO MVFR IN ANY SHRA. MOUNTAIN
OBSCURATIONS AND MECHANICAL TURBULENCE WILL BE POSSIBLE ACROSS MUCH
OF THE AREA IN THAT TIME FRAME.
&&

.SPOTTER INFORMATION STATEMENT...SPOTTER ACTIVATION IS NOT EXPECTED
THROUGH THURSDAY. SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT
WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES FRIDAY
THROUGH SUNDAY.
&&

$$

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

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