Snow Advisory 8, NWS Las Vegas, NV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
906 PM PST THU FEB 21 2008

.SYNOPSIS...A WEAK PACIFIC STORM WILL MOVE ACROSS THE AREA TONIGHT
AND FRIDAY RESULTING IN SCATTERED RAIN AND SNOW OVER THE AREA.
THERE WILL BE A BREAK ON SATURDAY BEFORE ANOTHER...STRONGER STORM
AFFECTS THE REGION ON SUNDAY. HIGH PRESSURE WILL THEN BUILD OVERHEAD
EARLY NEXT WEEK...FOR DRIER AND WARMER CONDITIONS.
&&

.UPDATE...RADAR DETECTING SMALL AREA OF LIGHT SHOWERS APPROACHING
THE LAS VEGAS VALLEY FROM THE SOUTHWEST. AN AUTOMATED GAGE AT
MOUNTAIN PASS ALONG I-15 IN NORTHEAST SAN BERNARDINO COUNTY MEASURED
0.04 INCHES AS THE BAND PASSED BY. THE AREA IS QUICKLY MOVING TO THE
EAST AND EXPECT ONLY A TRACE OR A FEW HUNDREDTH AT MOST IN THE
VALLEY. REGIONAL RADAR OVER CALIFORNIA SHOWS TWO DISTINCT AREA OF
PRECIPITATION WITH MOST OF THIS EXPECT TO SPLIT THE LAS VEGAS VALLEY
TONIGHT. ONE AREA CURRENTLY PUSHING THROUGH THE SOUTHLAND WILL SKIRT
ACROSS SOUTHERN SAN BERNARDINO COUNTY TONIGHT AND ACROSS SOUTHERN
MOHAVE COUNTY FRIDAY MORNING. THE SECOND AREA HAS BEEN PRODUCING
HEAVY SNOW IN THE SOUTHERN SIERRA WITH 10 INCHES OF NEW SNOW AT
ASPENDELL SINCE 3 PM. 00Z GFS/NAM IN AGREEMENT THAT MOST OF THIS
MOISTURE WILL MOVE NORTH OF LAS VEGAS ACROSS CENTRAL NYE AND LINCOLN
COUNTIES TONIGHT AND FRIDAY. A ZONE UPDATE HAS ALREADY BEEN ISSUED
AND REMOVED THE MENTION OF EARLY EVENING.
&&

.PREV DISCUSSION...330 PM PST THU FEB 21...WEAK SHORTWAVE PUSHING
ACROSS CALIFORNIA TO MOVE THROUGH THE CWA TONIGHT AND EARLY FRIDAY.
ALTHOUGH SLIGHT CHANCE/CHANCE POPS LOOKED FOR ACROSS MUCH OF THE
DISTRICT...BEST CHANCE OF PRECIPITATION WILL BE MOUNTAINS WITH
OROGRAPHIC COMPONENT PLAYING A BIG PART. HOWEVER OVERALL QPF TOTALS
SHOULD REMAIN LIGHT. WEAK SHORTWAVE RIDGE TO BUILD OVER THE AREA
FRIDAY NIGHT AND SATURDAY BEFORE NEXT STRONGER STORM FORMS OFF THE
CALIFORNIA COAST SATURDAY. THIS SYSTEM TO BEGIN MOVING INLAND LATE
SATURDAY WITH INCREASING PRECIPITATION INTO THE SOUTHERN SIERRA
SATURDAY NIGHT AND THEN ACROSS THE DISTRICT INTO THE LONG TERM. AS
THE FIRST SYSTEM CROSSES OVER THE AREA ON FRIDAY STABILITY WILL ONCE
AGAIN DECREASE ESPECIALLY ACROSS THE NORTHERN PORTION OF THE CWA AND
WILL INCLUDE A SLIGHT CHANCE OF AFTERNOON THUNDERSTORMS FOR THIS
AREA. ALSO INCREASED SURFACE PRESSURE GRADIENTS TO BRING GUSTY WINDS
TO WESTERN SAN BERNARDINO COUNTY FRIDAY AFTERNOON. AT THIS TIME
WINDS LOOK TO BE BELOW ADVISORY LEVELS. NEXT CONCERN IS SYSTEM OVER
THE WEEKEND. BEST QPF FOR SATURDAY NIGHT TO BE OVER THE WESTERN SIDE
OF THE SOUTHERN SIERRA...BUT ENOUGH DYNAMICS TO PUSH ACCUMULATING
SNOW ONTO THE EAST SIDE AND LOCALLY HEAVY AMOUNTS MAY BE SEEN OVER
THE HIGHER ELEVATIONS BY SUNDAY MORNING. GOOD SOUTHWEST FLOW TO ALSO
PRODUCE GUSTY WINDS ACROSS THE CREST...HOWEVER IT DOES NOT LOOK LIKE
WINDS WILL REACH INTO THE VALLEY ATTM. DECIDE NOT TO ISSUE A WINTER
STORM WATCH ATTM FOR THE EAST SLOPES...HOWEVER WILL BE WATCHING THE
DEVELOPMENT OVER THE NEXT COUPLE OF MODEL RUNS. WITH THE UNSETTLE
PATTERN CONTINUING INTO THE WEEKEND...DAYTIME TEMPS TO REMAIN
GENERALLY BELOW NORMAL.

.LONG TERM...GOOD OVERALL MODEL AGREEMENT ON NEXT SYSTEM ON SUNDAY.
ALL SHOW COPIOUS AMOUNTS OF MOISTURE COMING IN AND A DECENT AMOUNT
BEING DEPOSITED ON THE WINDWARD SIDE OF THE SIERRA. HOWEVER BELIEVE
AS IN OTHER SIMILAR AND RECENT SYSTEMS ENOUGH WILL MAKE IT OVER TO
BRING WIDE SPREAD CHANCES OF PRECIPITATION AREA WIDE SUNDAY AND INTO
EARLY MONDAY. STILL HAVE A POSSIBLE DOWN SLOPE WIND EVENT TO
CONSIDER WITH THIS SYSTEM IN THE SIERRA/OWENS VALLEY. HAVE LEFT THE
STRONGEST WIND ON THE HIGHER PEAKS AS I STILL EXPECT THE HEAVY
PRECIPITATION ON THE MOUNTAIN TO DRAG THE WINDS DOWN AS BOTH WILL
OCCUR AT THE SAME TIME. FURTHER...THIS FAR OUT IT IS HARD TO BE
PRECISE IN TIMING OF THIS AND BEST LEFT TO WHEN WE GET CLOSER TO THE
EVENT. OTHERWISE DID RAISE TEMPERATURES A TAD IN THE MIDWEEK ON.
RIDGING OVER THE WESTERN CONUS STARTS AND BUILD MONDAY ONWARD.
&&

.AVIATION...FOR MCCARRAN...A BAND OF LIGHT SHOWERS WILL MOVE ACROSS
THE LAS VEGAS VALLEY BETWEEN 05Z-07Z WITH CEILING DROPPING TO 6 KFT.
CONDITIONS SHOULD IMPROVE BY EARLY AFTERNOON FRIDAY WITH CEILING
ABOVE 5000 FT AND RAIN OUT OF THE AREA. NEXT PERIOD OF ACTIVE
WEATHER IS EXPECTED TO BEGIN SATURDAY NIGHT WITH THE NEXT STORM
SYSTEM.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...A STORM SYSTEM APPROACHING FROM CALIFORNIA WILL BRING
LOWER CEILINGS FROM WEST TO EAST THIS EVENING IN THE 3-5K FT RANGE
ALONG WITH WIDE SPREAD SHOWERS THROUGH THE AREA AND PERSIST THROUGH
THE MORNINGS HOURS FRIDAY. SNOW IS LIKELY OVER THE SIERRA AND
CENTRAL NEVADA MOUNTAINS. HIGHER CEILINGS WILL COME FRIDAY MORNING
AGAIN FROM WEST TO EAST AND BY LATE AFTERNOON THERE SHOULD LITTLE IF
ANY PRECIPITATION IN THE AREA.
&&

.VEF WATCHES/WARNINGS/ADVISORIES...
NV...NONE.
AZ...NONE.
CA...HEAVY SNOW WARNING UNTIL 4 AM PST FRIDAY FOR CAZ519.
&&

PIERCE/JENSEN/JACQUES

HTTP://WEATHER.GOV/LASVEGAS