FXUS65 KVEF 100358
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
758 PM PST WED DEC 9 2009

.SYNOPSIS...A DRY NORTHWEST FLOW OVER THE REGION WILL GIVE WAY TO 
INCREASING MOISTURE THURSDAY AND A WEAK PACIFIC SYSTEM MOVING INLAND 
FRIDAY. A STRONGER STORM AND ADDITIONAL MOISTURE WILL ONCE AGAIN 
BRING WIDESPREAD PRECIPITATION TO MUCH OF THE REGION SATURDAY AND 
SUNDAY...WITH SNOW MAINLY CONFINED TO ELEVATIONS ABOVE 5000 FEET.
&&

.UPDATE...CIRRUS BEGINNING TO WORK ITS WAY IN FROM THE WEST AS 
ADVERTISED. MAIN ISSUE FOR TONIGHT IS HOW COLD WILL IT GET. TEMPS 
ARE QUITE LOW THIS EVENING...HOWEVER...INCREASING CLOUDS WILL 
PROBABLY CAUSE THEM TO FLAT-LINE AT SOME POINT LATE THIS EVENING OR 
OVERNIGHT. CONFIDENCE IN THE DETAILS IS NOT HIGH ENOUGH TO WARRANT 
CHANGING LOW TEMP FORECASTS...WHICH LOOK QUITE REASONABLE ANYWAY. NO 
UPDATES PLANNED AT THIS TIME.
&&

.PREV DISCUSSION...
315 PM PST WED DEC 9 2009

.SHORT TERM...QUIET WEATHER TODAY AFTER A VERY COLD START TO THE 
MORNING. TEMPERATURES OVER THE NORTHERN HALF OF THE CWA DROPPED TO 
SOME OF THE COLDEST READINGS IN YEARS. OVERNIGHT LOWS WILL BE A 
LITTLE TRICKIER TONIGHT DUE TO AN INCREASE IN CIRRUS CLOUDS. HIGH 
CLOUDS ARE FORECAST TO PUSH ACROSS THE AREA BETWEEN 00Z-06Z AND 
BECOME THICKER OVERNIGHT. CURRENT THINKING IS THAT LOW TEMPERATURES 
WILL BE ABOUT 1-4 DEGREES WARMER AT MOST LOCATIONS...STILL LEAVING 
MANY NORTHERN CWA LOCATIONS AT OR BELOW ZERO. WEAK DIRTY RIDGE OVER 
THE AREA THURSDAY WITH VALLEY INVERSIONS ONCE AGAIN IN PLACE. CLOUDS 
WILL ALSO BEGIN TO THICKEN AND LOWER AHEAD OF A WEAK TROUGH PUSHING 
ONTO THE WEST COAST THURSDAY NIGHT AND FRIDAY. CURRENT MODELS 
CONTINUE TO SHOW THIS FIRST SYSTEM TO REMAIN RATHER WEAK AS IT 
PUSHES ACROSS THE AREA. MOISTURE IS EXPECTED TO START IN THE SIERRA 
EARLY FRIDAY MORNING WITH SNOW LEVELS ABOVE 6000 FEET. HEAVIEST SNOW 
AMOUNTS ARE EXPECTED TO REMAIN OVER THE WESTERN SLOPES...BUT A FEW 
INCHES OF SNOW MAY FALL OVER THE HIGHER ELEVATIONS OF THE EASTERN 
SIERRA. MODELS ARE ALSO SHOWING SOME PACIFIC MOISTURE BEING PULLED 
NORTHWARD INTO THE LOWER DESERTS FRIDAY AFTERNOON. MOST VALLEY 
LOCATIONS WILL SEE A SLIGHT CHANCE OF POPS WITH A BETTER CHANCE AT 
THE HIGHER ELEVATIONS. A STRONGER AND WETTER STORM STILL LOOKS TO BE 
ON TRACK FOR SATURDAY ACROSS THE ENTIRE CWA. 

.LONG TERM...MODELS CONTINUE TO POINT TO SATURDAY AS THE BEST DAY 
FOR ANOTHER DECENT SHOT OF QPF ACROSS THE SOUTHERN GREAT BASIN. THE 
GREATEST PRECIPITATION AMOUNTS ARE FORECAST OVER THE CENTRAL AND 
NORTHERN CWA WHERE .25 TO .75 INCHES OF LIQUID ARE POSSIBLE. HIGHER 
AMOUNTS WILL GENERALLY BE FOUND IN THE SIERRA WHERE GREATER THAN AN 
INCH ARE LIKELY. AMOUNTS ALONG THE FAR SOUTHERN REGIONS SHOULD BE ON 
THE LIGHTER SIDE AND GENERALLY UNDER .25 INCHES. THIS AIRMASS IS 
EXPECTED TO ON THE MILDER SIDE WITH SNOW LEVELS REMAINING ABOVE 5000 
FEET CENTRAL AND SOUTH AND ABOVE 4000 FEET NORTH. WINTER WEATHER 
PRODUCTS WILL PROBABLY BE NECESSARY AT SOME POINT IN THE NEXT DAY OR 
TWO AS TIMING AND AMOUNTS ARE NAILED DOWN. WINDS ARE EXPECTED TO 
BECOME GUSTY FROM THE SOUTH LATE SATURDAY INTO SUNDAY AND WILL HAVE 
TO BE EVALUATED AS THE TIME NEARS FOR POTENTIAL WIND WWA PRODUCTS. 
THE STORM WILL BE EXITING THE AREA SUNDAY AND CONDITIONS WILL 
IMPROVE BEHIND IT. WEAK RIDGING FOLLOWS NEXT WEEK BUT THERE IS A LOT 
OF UNCERTAINTY IN THE EXTENT AS MODEL SOLUTIONS VARY IN THEIR 
DEPICTION OF THE EVOLVING WEATHER PATTERN.

.AVIATION...FOR MCCARRAN...LIGHT AND VARIABLE WINDS THROUGH FRIDAY. 
INCREASING CLOUDS ARE EXPECTED OVERNIGHT AND THURSDAY BECOMING BKN 
AOA 25K FEET TONIGHT WITH FEW-SCT 15K FEET DEVELOPING THURSDAY. THE 
NEXT STORM SYSTEM IS EXPECTED TO BRING ANOTHER ROUND OF WIND...RAIN 
AND LOW CEILINGS TO THE AIRPORT DURING THE FRIDAY TO SUNDAY MORNING 
TIME FRAME.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST 
CALIFORNIA...LIGHT WINDS MAINLY FOLLOWING NORMAL DIURNAL DIRECTIONAL 
TRENDS THROUGH FRIDAY. INCREASING CLOUDS AOA 25K FEET TONIGHT AND 
THURSDAY WITH SCT 12-15K FEET DEVELOPING LATE TONIGHT. A STORM WILL 
BRING IMPACTS TO THE AREA FRIDAY THROUGH SUNDAY WITH THE POTENTIAL 
FOR WIND...RAIN AND LOWER CEILINGS ONCE AGAIN.
&&

.VEF WATCHES/WARNINGS/ADVISORIES...
NV...NONE.
AZ...NONE.
CA...NONE.
&&

$$

MORGAN/GORELOW/SALMEN

HTTP://WEATHER.GOV/LASVEGAS