Weather Service Report


743 
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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