FXUS65 KVEF 110332
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
732 PM PST THU DEC 10 2009

.SYNOPSIS...A COUPLE OF DISTURBANCES IN A MOIST WESTERLY FLOW WILL 
BRING MOUNTAIN SNOW AND VALLEY RAIN TO THE REGION LATE TONIGHT 
THROUGH SUNDAY NIGHT. THE BEST CHANCE OF PRECIPITATION WILL BE 
SATURDAY THROUGH SATURDAY NIGHT AS THE STRONGER OF THE DISTURBANCES 
MOVES THROUGH. SIGNIFICANT SNOWFALL WILL BE POSSIBLE ABOVE 5000 FEET
DURING THIS TIME FRAME. TEMPERATURES WILL REMAIN BELOW NORMAL 
THROUGH SUNDAY. HIGH PRESSURE WILL BRING DRY CONDITIONS MUCH OF NEXT 
WEEK.
&&

.UPDATE...RADAR ECHOES WERE MOVING THROUGH KERN COUNTY...WHERE LIGHT 
RAIN HAD BEEN REPORTED...INTO FAR WESTERN SAN BERNARDINO COUNTY AT 
730 PM. CURRENT FORECAST HAS THIS COVERED WELL. MAIN CONCERN FOR 
THIS EVENING IS WET BULB TEMPERATURES NEAR FREEZING IN THE AREAS 
WHERE RADAR ECHOES ARE APPROACHING. WILL KEEP AN EYE ON THIS AND MAY 
NEED TO UPDATE LATER DEPENDING ON INITIAL REPORTS AS THE PRECIP 
BEGINS.
&&

.PREV DISCUSSION...
310 PM PST THU DEC 10 2009

.SHORT TERM...FORECAST SOMEWHAT TRICKY THROUGH SUNDAY NIGHT WITH A 
FAIRLY MOIST BUT LOW AMPLITUDE FLOW ACROSS THE REGION. MODELS SEEM 
TO BE CHANGING LOCATION...TIMING AND INTENSITY OF PRECIPITATION AND 
SHORTWAVES WITH EACH RUN. 

WEAK RIDGING OVER THE AREA THIS EVENING WILL MOVE QUICKLY EAST AS A 
WEAKENING SHORTWAVE CURRENTLY JUST OFF SHORE MOVES THROUGH 
CALIFORNIA. THIS FEATURE WILL BRING A SHOT OF SNOW TO THE SIERRA 
TONIGHT INTO FRIDAY WITH A FEW INCHES POSSIBLE AT HIGHER ELEVATIONS. 
CHANCES OF PRECIPITATION WILL SPREAD THROUGH INYO AND MUCH OF SAN 
BERNARDINO COUNTY OVERNIGHT AND EVEN INTO WESTERN NEVADA. 

ALL ZONES WILL HAVE A CHANCE OF LIGHT PRECIPITATION FRIDAY AS THE 
WEAK SHORTWAVE CONTINUES TO MOVE ACROSS NEVADA IN THE MOIST FLOW 
WITH SNOW LEVELS AROUND 5000 FEET. PRECIPITATION SHOULD GENERALLY 
DECREASE FROM THE WEST IN THE AFTERNOON AS THE SHORTWAVE EXITS TO 
THE EAST. 

THE NEXT...MORE SIGNIFICANT TROUGH LOOKS TO BE PROGRESSING A BIT 
SLOWER NOW BUT IT IS PICKING UP A DECENT AMOUNT OF MOISTURE WHICH 
WILL SPREAD ACROSS THE AREA FRIDAY NIGHT THROUGH SATURDAY. RAIN AND 
SNOW WILL BECOME LIKELY IN THE SIERRA BY FRIDAY NIGHT WITH LIKELY 
POPS ACROSS MOST OF THE FORECAST AREA SATURDAY. MY CONCERN ABOUT 
SATURDAY IS THE LACK OF DYNAMICS WHICH MAY LIMIT PRECIPITATION 
SATURDAY. SATURDAY NIGHT LOOKS BETTER FOR DECENT PRECIPITATION AS 
THE TROUGH AXIS MOVES INTO THE AREA. DUE TO THE UNCERTAINTY 
MENTIONED EARLIER...OPTED NOT TO CHANGE WINTER STORM WATCHES FOR THE 
INYO AND CLARK COUNTY MOUNTAINS BUT IF CURRENT TRENDS CONTINUE WITH 
LATER RUNS...A WATCH/WARNING MAY BE NEEDED FOR SATURDAY NIGHT INTO 
SUNDAY FOR CENTRAL NYE AND LINCOLN COUNTIES. 

THE TROUGH AXIS WILL GRADUALLY MOVE EAST OF THE AREA SUNDAY INTO 
SUNDAY NIGHT WITH PRECIPITATION CHANCES DECREASING FROM THE WEST. 

.LONG TERM...TROUGH TO EXIT THE AREA EARLY MONDAY AS HIGH PRESSURE 
MOVE INTO THE WESTERN U.S.. MODELS ARE INDICATING SOME RESIDULE 
MOISTURE REMAINING OVER THE FAR EASTERN AREAS OF THE CWA MONDAY 
MORNING...MAINLY MOHAVE COUNTY...WITH CLEARING EXPECTED DURING THE 
AFTERNOON. HIGH PRESSURE WILL THEN BUILD OVER THE CWA TUESDAY 
THROUGH THURSDAY WITH LIGHT WINDS AND DRY CONDITIONS. MAIN CONCERNS 
THROUGH THE EXTENDED WILL BE DAILY VALLEY INVERSIONS. THIS SHOULD 
KEEP MOST LOCATIONS SEVERAL DEGREES BELOW NORMAL AND HAVE UNDERCUT 
GUIDANCE BY A FEW DEGREES.  

.AVIATION...FOR MCCARRAN...LIGHT AND VARIABLE WINDS TO CONTINUE 
THROUGH TONIGHT WITH VARYING AMOUNTS OF CLOUD COVER AOA 20K FEET. A 
SERIES OF STORM SYSTEMS WILL BRING THE POSSIBILITY OF LOW CEILINGS 
AND RAIN TO THE AIRPORT STARTING FRIDAY NIGHT INTO SATURDAY MORNING 
AND EXIT BY SUNDAY AFTERNOON. THE MOST LIKELY TIME FOR RAIN IN THE 
VALLEY RIGHT NOW LOOKS TO BE FRIDAY AFTERNOON WITH A BETTER CHANCE 
LATE SATURDAY AFTERNOON AND NIGHT. HOWEVER...A FEW SHOWERS MAY 
DEVELOP OVER THE MOUNTAINS WEST OF LAS VEGAS AS EARLY AS 12Z FRIDAY. 

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST 
CALIFORNIA...LIGHT WINDS MAINLY FOLLOWING NORMAL DIURNAL DIRECTIONAL 
TRENDS THROUGH TONIGHT. TWO STORM SYSTEMS ARE FORECAST TO AFFECT THE 
AREA THROUGH SUNDAY WITH THE FIRST MOVING IN LATE TONIGHT THROUGH 
FRIDAY. CLOUDS WILL GRADUALLY LOWER THIS EVENING ACROSS INYO COUNTY 
TO AROUND 6K-8K FEET AND GRADUALLY SHIFT EAST. MOST LOCATIONS WILL 
SEE A CHANCE OF RAIN AND SNOW FRIDAY WITH CIGS GENERALLY AROUND 
8K-10K FEET. SNOW LEVELS ARE FORECAST TO BE ABOUT 5K FEET ACROSS THE 
NORTH AND 6K FEET IN THE SOUTH. 
&&

.VEF WATCHES/WARNINGS/ADVISORIES...
NV...WINTER STORM WATCH FROM SATURDAY MORNING THROUGH SUNDAY 
     AFTERNOON FOR NVZ018-019.
AZ...NONE.
CA...WINTER STORM WATCH FROM LATE FRIDAY NIGHT THROUGH LATE SATURDAY 
     NIGHT FOR CAZ519-521-522.
&&

$$

MORGAN/HARRISON/GORELOW

HTTP://WEATHER.GOV/LASVEGAS