FXUS65 KVEF 281827 AAA
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
1028 AM PST SAT NOV 28 2009

.SYNOPSIS...AN AREA OF LOW PRESSURE OVER SOUTHERN CALIFORNIA WILL 
IMPACT THE AREA WEATHER OVER THE WEEKEND WITH INCREASING 
CLOUDS...WIND...A CHANCE OF SHOWERS AND COOLER TEMPERATURES. 
CONDITIONS ARE EXPECTED TO IMPROVE LATE SUNDAY INTO MONDAY AS THE 
LOW MOVES WELL SOUTHEAST OF THE AREA AND IS REPLACED BY HIGH 
PRESSURE.
&&

.UPDATE...THE LOW IS CURRENTLY CENTERED OVER WESTERN SAN BERNARDINO 
COUNTY AND IS FORECAST TO MOVE SOUTHEAST OVER THE NEXT SEVERAL DAYS. 
SKIES HAVE CLEARED OVER MUCH OF THE SOUTHEAST CWA THIS MORNING BUT 
SHOULD BEGIN TO FILL IN AGAIN BY THE AFTERNOON. MODIFIED THE SKY 
GRID TO BETTER REFLECT THE CURRENT CONDITIONS AND WHAT IS EXPECTED 
FOR THIS AFTERNOON. POPS WERE ALSO BEEFED UP A BIT ACROSS THE 
SOUTHERN CWA DUE TO DECENT AGREEMENT BETWEEN MORNING MODELS WITH 
PRECIPITATION DEVELOPING OVER THE FLAGSTAFF CWA AND THEN MOVING 
WESTWARD INTO THE VEGAS CWA. MAIN AREAS OF CONCERN FOR AFTERNOON AND 
EVENING SHOWERS AND THUNDERSTORMS ARE ACROSS MOHAVE...CLARK...INYO 
AND SAN BERNARDINO COUNTIES WITH SMALLER CHANCES FURTHER NORTH. 
TEMPERATURES ARE RUNNING A DEGREE OR TWO ABOVE OR BELOW THOSE OF 24 
HRS AGO BUT AS THE CLOUDS FILL IN...HEATING SHOULD STALL OVERALL. 
FORECAST QPF AMOUNTS FOR TODAY/TONIGHT WILL GENERALLY BE LESS THAN 
.10 INCHES WITH SOME AREAS POTENTIALLY SEEING UP TO .25 INCHES. 
LOCALLY HEAVIER AMOUNTS ARE POSSIBLE ALONG EAST FACING SLOPES OF 
MOHAVE AND CLARK COUNTIES AS FAVORABLE UPSLOPE FLOW DEVELOPS LATER 
THIS AFTERNOON IN THESE AREAS. 
&&

.PREVIOUS DISCUSSION...418 AM PST...

.SHORT TERM...UPPER LOW IS OVER THE SOUTHERN SAN JOAQUIN VALLEY 
EARLY THIS MORNING. LIGHT RAIN STARTED TO FALL AT BISHOP JUST BEFORE 
MIDNIGHT WITH EDWARDS RADAR DETECTING OTHER AREAS OF SHOWERS ACROSS 
SOUTHERN INYO AND WESTERN SAN BERNARDINO COUNTIES. RAINFALL TOTALS 
SO FAR AT BISHOP AND INDEPENDENCE ARE LESS THAN A TENTH OF AN INCH. 
INFRARED IMAGERY INDICATES ENHANCED CLOUDS ASSOCIATED WITH 
DEFORMATION ZONE OVER WESTERN NEVADA AND UPSLOPE NORTHEAST WINDS 
ALONG THE EAST SLOPES OF THE SOUTHERN SIERRA IN INYO AND MONO 
COUNTIES. DID HOIST A WINTER WEATHER ADVISORY FOR SNOW ALONG THE 
EAST SLOPES OF THE SOUTHERN SIERRA TODAY. AM ESTIMATING 3 INCHES OF 
NEW SNOW THROUGH 2 AM FROM AN AUTOMATED GAGE NEAR SOUTH LAKE. SOME 
AREAS SHOULD SEE ANOTHER 3 INCHES THROUGH MID MORNING BEFORE 
DYNAMICS AND UPSLOPE WINDS WEAKEN. 

HIGH CLOUD SHIELD WILL BE EXITING MOHAVE COUNTY SHORTLY LEAVING THE 
EASTERN HALF OF THE AREA IN A RELATIVELY CLEAR SLOT. HOWEVER...DON'T 
ANTICIPATE THE CLEAR SLOT LASTING LONG AS CLOUDS SHOULD FILL IN AS 
AREA OF INSTABILITY/LIFT ASSOCIATED WITH LOW WORKS OVER THE AREA. 
CONVECTIVE SHOWERS SHOULD FAVOR THE HIGHER TERRAIN THIS AFTERNOON 
NEAR THE LOW CENTER BUT CAN NOT RULE OUT AT LEAST A SLIGHT CHANCE 
FOR THE VALLEYS. KEPT THE IDEA FROM PREVIOUS SHIFT MENTIONING 
THUNDERSTORMS ACROSS SAN BERNARDINO/SRN CLARK AND MOHAVE COUNTIES. 
FOR TONIGHT...NAM/GFS REMAIN CONSISTENT DEVELOPING A BAND OF 
PRECIPITATION ACROSS CLARK COUNTY AGAIN ASSOCIATED WITH AN AXIS OF 
DEFORMATION. DECIDED TO ISSUE A WINTER WEATHER ADVISORY FOR SNOW IN 
THE SPRING MOUNTAINS AND SHEEP RANGE AS AN EASTERLY COMPONENT TO THE 
WIND COULD HELP ENHANCE SNOWFALL IN KYLE AND LEE CANYONS FOR A BRIEF 
TIME THIS EVENING. OTHER CONCERN TODAY WILL BE THE NORTH WINDS 
DEVELOPING...ESPECIALLY ACROSS THE NORTHERN ZONES AS THE PRESSURE 
GRADIENT INCREASES. THE AREA AROUND BISHOP WILL NEED TO BE MONITORED 
AS FORECAST CALLS FOR GUSTS TO 40 MPH. 

FOR SUNDAY AND MONDAY...UPPER LOW WILL SAG SOUTH INTO NORTHWEST 
MEXICO THEN MOVE EAST TOWARD THE BIG BEND AREA OF TEXAS BY 12Z 
TUESDAY. ISOLATED SHOWERS ASSOCIATED WITH WEAKENING DEFORMATION AXIS 
WILL COME TO AN END SUNDAY AFTERNOON ACROSS THE FAR SOUTHERN ZONES. 
DRY AND SLIGHTLY WARMER MONDAY.                         

.LONG TERM...LESS UNCERTAINTY IN THE EXTENDED AS OPERATIONAL RUNS OF 
GFS AND ECMWF COMING CLOSER WITH THEIR DEPICTION OF THE NEXT WAVE TO 
ENTER THE PICTURE ON WEDNESDAY. HOWEVER THERE IS STILL ENOUGH 
DIFFERENCES TO KEEP CONFIDENCE IN DETAILS LOW. TUESDAY STARTS OUT 
WITH RIDGING AS THE WEEKEND SYSTEM IS OVER THE TEXAS BIG BEND AREA 
AND NEXT SYSTEM WELL OFF SHORE. MODELS DIFFER IN TRACK OF THIS OFF 
SHORE SYSTEM AND ENSEMBLE SPREAD SOMEWHAT VAGUE. BUT SUFFICE TO SAY 
A TROUGH WILL QUICKLY MOVE THROUGH WEDNESDAY. DID ADJUST THE VERY 
LOW VALUE POPS TO WEDNESDAY / THURSDAY TO REFLECT THE PASSAGE TIME 
BUT THEY ARE STILL TOO LOW TO SHOW IN TEXT FORECASTS. FROM THURSDAY 
ON...MODELS AGAIN WIDELY DIVERGE BETWEEN HAVING ANOTHER SYSTEM AND 
STRONGER SYSTEM DROP SOUTH IN CALIFORNIA...GFS/GEM OR AN INSIDE 
SLIDER TO OUR EAST PER THE ECMWF. THIS WILL BE JUST BEYOND THE 
EXTENDED SO WILL WORRY ABOUT IT LATER.
&&

.AVIATION...FOR MCCARRAN...A LOW PRESSURE SYSTEM IN CENTRAL 
CALIFORNIA WILL MOVE SOUTH OF NEVADA AND BRING WITH INCREASING CLOUD 
COVER IN THE AFTERNOON. CEILINGS WILL BE IN THE 8-12K RANGE WITH A 
CHANCE OF LIGHT RAIN IN THE VICINITY THIS AFTERNOON. WINDS WILL ALSO 
SWITCH OVER FROM THE USUAL NIGHT TIME SOUTHWEST TO NORTHEAST IN THE 
AFTERNOON WITH THE TIMING NOT THAT CERTAIN BUT SURE SPEEDS WILL BE 
ABOVE 10 KNOTS. CLOUDS AND WINDS WILL DECREASE SUNDAY AFTERNOON.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST 
CALIFORNIA...A LOW PRESSURE SYSTEM IN CENTRAL CALIFORNIA THIS 
MORNING WILL TRACK SOUTH-SOUTHEAST TODAY TOWARDS THE NORTHERN GULF 
OF CALIFORNIA BY SUNDAY AFTERNOON. THIS WILL BRING INCREASING CLOUD 
COVER TODAY AND INTO SUNDAY. SNOW IS LIKELY IN THE SIERRA AND 
SOUTHERN NEVADA MOUNTAINS TODAY AND TONIGHT WITH LOWER LIKELIHOOD OF 
RAIN OVER SOUTHERN NEVADA AND CALIFORNIA TODAY AND NORTHWEST ARIZONA 
SUNDAY MORNING. CEILINGS SHOULD AVERAGE 6-8K MSL AREAWIDE TODAY 
THROUGH SUNDAY AFTERNOON. WINDS WILL GENERALLY BE LIGHT FROM THE 
SOUTH AHEAD OF THE SYSTEM AND THEN SHIFT NORTHERLY BEHIND AS IT 
PASSES.
&&

.CLIMATE...SO FAR THROUGH FRIDAY NOVEMBER 27 THE AVERAGE TEMPERATURE 
FOR NOVEMBER AT MCCARRAN INTERNATIONAL AIRPORT HAS BEEN 59.6 
DEGREES. GIVEN THE CURRENT FORECASTED NUMBERS THERE IS SOME 
POTENTIAL FOR LAS VEGAS TO SEE THIS NOVEMBER RANK AMONG THE 10 
WARMEST ON RECORD. THE WARMEST NOVEMBERS ON RECORD AT LAS VEGAS 
ARE...

1. 60.9 DEGREES IN 2007
2. 60.8 DEGREES IN 2008
3. 59.8 DEGREES IN 1995
4. 59.3 DEGREES IN 2005
5. 58.9 DEGREES IN 1949
6. 58.8 DEGREES IN 1999
7. 58.6 DEGREES IN 2001
8. 58.4 DEGREES IN 2006
9. 58.0 DEGREES IN 1976 AND 1981
&&

.VEF WATCHES/WARNINGS/ADVISORIES...
NV...WINTER WEATHER ADVISORY FROM 2 PM THIS AFTERNOON TO 4 AM PST 
     SUNDAY FOR NVZ018-019.
AZ...NONE.
CA...WINTER WEATHER ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR 
CAZ519. &&

$$

PIERCE/JACQUES

HTTP://WEATHER.GOV/LASVEGAS