Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000
FXUS65 KVEF 191024
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
223 AM PST FRI DEC 19 2014

.SYNOPSIS...A WEAK SYSTEM WILL MOVE ACROSS THE AREA TODAY THROUGH
SATURDAY MARKED MAINLY BY AN INCREASE IN CLOUD COVER. A FEW LIGHT
SHOWERS WILL BE POSSIBLE IN THE HIGHER ELEVATIONS OF THE SOUTHERN
GREAT BASIN. HIGH PRESSURE IS EXPECTED TO STRENGTHEN OFF THE COAST
OF CALIFORNIA ON SUNDAY AND HOLD THROUGH TUESDAY KEEPING THE AREA
DRY AND MILD. ANOTHER SYSTEM MAY IMPACT THE AREA CHRISTMAS EVE INTO
CHRISTMAS DAY.
&&

.SHORT TERM...TODAY THROUGH SUNDAY NIGHT.

CLOUDS ARE ONCE AGAIN IN THE FORECAST FOR TODAY AS ANOTHER MID/UPPER
LEVEL TROUGH ROLLS ON IN FROM THE PACIFIC. MOST OF THE MOISTURE WITH
THIS INCOMING SYSTEM WILL REMAIN ABOVE 15000 FEET WHICH WILL
TRANSLATE INTO A LOT OF HIGH LEVEL CLOUDS ACROSS MOST OF THE AREA
TODAY FOLLOWED BY MID AND HIGH LEVEL CLOUDS AS THIS SYSTEM PASSES
ACROSS THE AREA TONIGHT INTO SATURDAY. IT IS WORTH NOTING THAT SO
FAR THIS MONTH LAS VEGAS HAS ONLY HAD 1 DAY THAT COUNTS AS CLEAR
BASED ON SUNRISE TO SUNSET AVERAGE SKY COVER OF 30 PERCENT OR LESS.
NEITHER TODAY OR TOMORROW WILL ADD TO THAT COUNT. ACROSS THE HIGHER
ELEVATIONS OF THE SOUTHERN GREAT BASIN A FEW LIGHT SHOWERS MAY BE
SQUEEZED OUT LATE THIS AFTERNOON THROUGH SATURDAY. SNOW LEVELS WILL
BE BETWEEN 6000 AND 6500 FEET. TEMPS TODAY SHOULD BE CLOSE TO WHAT
WE SAW YESTERDAY WITH NOT MUCH GAIN EXPECTED DUE TO THE INCREASE IN
CLOUDS. TEMPS ON SATURDAY LOOK ABOUT THE SAME AS TODAY BASED ON
FORECAST SOUNDINGS. A BLEND OF THE BETTER PERFORMING BIAS CORRECTED
CONS MODELS AND MOS GUIDANCE WAS USED FOR TEMPS.

HIGH PRESSURE ALOFT IS EXPECTED TO BUILD INTO THE EASTERN PACIFIC
OFF OF CALIFORNIA SATURDAY NIGHT THROUGH SUNDAY NIGHT AND
STRENGTHEN. THIS WILL KEEP THE AREA DRY WITH A WARMING TREND,
HOWEVER, THIS WILL SET UP ENOUGH OF AN INVERSION TO KEEP THE LOWER
VALLEYS WEAKLY MIXED AND THUS AREAS BELOW THE INVERSION HEIGHT WILL
ONLY WARM UP MODESTLY TO ABOUT 4-6 DEGREES ABOVE NORMAL AT BEST.
SURFACE PRESSURE GRADIENTS TIGHTEN STARTING SUNDAY NIGHT AS A
SURFACE HIGH SETTLES INTO NORTHERN NEVADA. THIS WILL INCREASE WINDS
SOME IN THE COLORADO RIVER VALLEY.

.LONG TERM...MONDAY THROUGH CHRISTMAS DAY.

STRONG HIGH PRESSURE OVER THE EASTERN PACIFIC WILL BE THE MAIN
FEATURE MONDAY AND TUESDAY. NORTHERLY FLOW DOWN THE FRONT SIDE OF
THE RIDGE WILL RESULT IN LOCALLY BREEZY NORTH WINDS MONDAY AND
TUESDAY...ESPECIALLY DOWN THE COLORADO RIVER VALLEY. THE ENHANCED
MIXING COULD ALSO BRING SOME UNSEASONABLY WARM WEATHER TO THE WINDY
SPOTS. BY TUESDAY NIGHT THE MODELS START TO DIVERGE A BIT...BUT
AGREE ON A SHORTWAVE TROUGH APPROACHING THE PACIFIC NORTHWEST. THIS
WILL WEAKEN THE RIDGE AND REVERSE THE PRESSURE GRADIENTS AS IT
SWINGS TOWARD NORTHERN CALIFORNIA WEDNESDAY. TIMING AND STRENGTH
DETAILS ARE UNCLEAR...BUT THERE IS SOME CHANCE OF STRONG WESTERLY
WINDS WEDNESDAY AND/OR CHRISTMAS DAY AS THE STORM ROLLS THROUGH THE
GREAT BASIN. CANNOT RULE OUT SOME PRECIP CHANCES AS WELL...BUT FOR
NOW LIMITED ANY MENTION OF WEATHER TO THE SOUTHERN GREAT BASIN. IF
THE STORM ACTUALLY TRACKS FARTHER NORTH OR EAST...IMPACTS WOULD BE
LESS...BUT IF IT TRACKS FARTHER SOUTH OR WEST...THE MAIN FOCUS COULD
SHIFT FROM WIND TO PRECIP. EITHER WAY...TEMPERATURES WILL COME DOWN
QUITE A BIT FROM TUESDAY TO CHRISTMAS DAY.
&&

.AVIATION...FOR MCCARRAN...MAINLY BKN CLOUDS WITH BASES LOWERING
FROM AROUND 25K FEET TO 15K FEET FT ARE EXPECTED THROUGH THIS
EVENING. WINDS SHOULD BE 6 KTS OR LESS AND FAVOR TYPICAL DIURNAL
DIRECTIONAL TRENDS.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...PATCHY BR/FG IN AREAS FROM KIGM NORTH AND EAST
INCLUDING IN AND AROUND KACZ. VSBY HERE MAY BE MVFR OR LOWER.
SCT-BKN CLOUDS AOA 25K FEET WITH BASES LOWERING TO 10-15K FEET
THROUGH TONIGHT. THE LOWEST BASES THIS AFTERNOON INTO TONIGHT SHOULD
BE IN AND AROUND KBIH. WINDS WILL BE 6 KTS OR LESS AND TREND TOWARD
TYPICAL DIURNAL DIRECTIONS THROUGH TONIGHT.
&&

.SPOTTER INFORMATION STATEMENT...SPOTTER ACTIVATION IS NOT EXPECTED.
&&

$$

SHORT TERM/AVIATION...STACHELSKI
LONG TERM...MORGAN

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