National Weather Service Raw Text Product

165 
FXUS65 KVEF 202250
AFDLAS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
348 PM PDT WED OCT 20 2004

.SYNOPSIS...A MAJOR PRECIPITATION EVENT IS UNDERWAY ACROSS THE 
SOUTHERN GREAT BASIN AND MOJAVE DESERT. THE BAND OF STEADY RAIN IS 
FORECAST TO MOVE INTO NORTHWEST ARIZONA OVERNIGHT. THERE WILL BE 
SUFFICIENT MOISTSURE AND INSTABILITY TO SUPPORT SCATTERED AFTERNOON 
SHOWERS AND A SLIGHT CHANCE OF THUNDERSTORMS OVER THE REGION 
THURSDAY AFTERNOON. COOL AND DRY CONDITIONS WILL PREVAIL FRIDAY. 
&&

.SHORT TERM...SURFACE FRONTAL ZONE EXTENDED FROM ELY TO LAS VEGAS TO 
BARSTOW AT 22Z. SEVERAL LOWER DESERT LOCATIONS HAVE RECEIVED OVER AN 
INCH OF RAIN IN THE PAST 12 HOURS OR SO. SNOW LEVELS ACTUALLY LIFTED 
LAST NIGHT IN THE BROAD WARM ADVECTION ZONE AHEAD OF THE FRONT. AS A 
RESULT ALL THE PRECIP WAS LIQUID AT MOST OF THE REPORTING LOCATIONS. 
ON AVERAGE THE HIGHER ELEVATIONS RECEIVED ABOUT 3-5 INCHES OF RAIN 
IN THE PAST 24 HOURS. MT CHARLESTON HAS OFFICIALLY REPORTED AN 
ASTOUNDING 9.18 OF RAIN WE ARE INVESTIGATING CLIMATE RECORDS TO 
SEE WHERE THIS EVENT RANKS. I SUSPECT IT IS AN ALL-TIME RECORD FOR 
24-HOUR RAINFALL AT MT CHARLESTON...AND IT MAY WELL BE A RECORD FOR 
THE ENTIRE STATE. DESPITE THAT AMAZING AMOUNT OF RAIN THERE HAVE 
BEEN NO REPORTS OF FLOODING PROBLEMS. CANNOT FIGURE OUT WHY THERE IS 
NO RESPONSE IN THE STREAMS AND CANYONS UP THERE BUT OUR SOO IS ON 
THE MOUNTAIN NOW LOOKING INTO IT. RAIN IS REPORTEDLY NOW MIXING WITH 
SNOW AT THE LODGE. WE MAY SEE A COUPLE INCHES OF ACCUMULATION BEFORE 
IT ENDS COMPLETELY BUT THE WORST OF IT IS OVER. SNOW LEVELS WERE 
MUCH LOWER IN OUR SIERRA ZONE WHERE SPOTTERS REPORTED 14 INCHES OF 
NEW SNOW OVERNIGHT. MOST OF THE LAS VEGAS VALLEY GOT A NICE SOAKING 
RAIN OF ABOUT A THIRD TO A HALF INCH WITH A FEW SITES RECORDING 
NEARLY AN INCH. SOME OF THE CHANNELS AND WASHES ARE RUNNING BUT NO 
SERIOUS PROBLEM ARE EXPECTED. WILL ALLOW THE URBAN AND SMALL STREAM 
FLOOD ADVISORY TO EXPIRE ON SCHEDULE AT 430 PM BUT SOME ADDITIONAL 
RAINS COULD DEVELOP AS TAIL OF VORTICITY LOBE ROTATING THROUGH 
WESTERN NEVADA OVERSPREADS BACK END OF FRONTAL ZONE. HEAVY RAINS 
WILL SHIFT TO NORTHWEST ARIZONA AND THE LOWER COLORADO RIVER VALLEY 
AS FRONT SAGS SOUTHEASTWARD TONIGHT. TOMORROW...STEEP LAPSE RATES 
ASSOCIATED WITH THE UPPER COLD TROUGH COMBINED WITH PLENTY OF 
RESIDUAL MOISTURE WILL BE SUFFICIENT FOR SCATTERED AFTERNOON 
SHOWERS. AIR MASS MAY EVEN BE UNSTABLE ENOUGH TO SUPPORT ISOLATED 
LOW-TOPPED THUNDERSTORMS. UPPER TROUGH IS FORECAST TO PUSH EAST 
THURSDAY NIGHT LEADING TO A DRY NORTHWEST FLOW. WE WILL SEE SOME 
MODEST WARMING FRIDAY AND SATURDAY BUT TEMPERATURES WILL REMAIN 
BELOW NORMAL THROUGH THE WEEKEND. 

FOR OUR FIRE WEATHER CUSTOMERS...THIS PRECIP EVENT HAS EFFECTIVELY 
ENDED THE WILDFIRE SEASON. WE WILL ASSUME OFF SEASON OPERATIONS IN 
LAS VEGAS IMMEDIATELY.         

&&

.LONG TERM...WENT WITH THE GFS ENSEMBLE MEAN AS PRIMARY GUIDANCE FOR 
THE EXTENDED. OPERATIONAL GFS IS NOT TOO FAR OFF THE MEAN...BUT NOT 
AS DEEP...WHILE EURO IS STILL A BIT SLOWER AND NOT AS STRONG IN NEXT 
MAJOR SYSTEM TO ARRIVE TUESDAY. CANADIAN IS SIMILAR TO GFS BUT NOT 
AS STRONG. SUNDAY THROUGH MONDAY WILL SEE A WEAK TROUGH MIGRATE 
THROUGH WITH MOST MOISTURE BEING NORTH OF CWA. KEPT POPS IN THE 
NORTH WITH THIS SYSTEM. NEXT MAJOR SYSTEM APPROACHES ON TUESDAY AND 
WEDNESDAY. KEPT AND IN SOME CASES INCREASED THE POPS I INHERITED. BY 
WEDNESDAY EXPECT TO SEE POPS OVER ALL THE CWA. LOOKING FURTHER OUT 
ON THURSDAY IT COULD GET INTERESTING AROUND HERE IF GFS VERIFIES 
WITH CUT OFF BEARING DOWN ON TOP OF US. 
&&

.AVIATION...THE PRECIPITATION WILL TAPER OFF IN INTENSITY DURING THE 
EARLY EVENING SO THAT BY 04Z ONWARDS THERE IS ONLY A SLIGHT CHANCE 
OF RAIN FOR THE REST OF THE NIGHT. VISIBILITIES AND CEILINGS SHOULD 
NOT BE A PROBLEM AND THE 00Z TAF WILL REFLECT THIS. NEXT ITEM OF 
CONCERN WILL BE A SLIGHT CHANCE FOR THUNDERSTORMS AT KLAS THURSDAY 
AFTERNOON AS UPPER LEVEL TROUGH MOVING OVER SOUTHERN NEVADA WILL 
DESTABILIZE THE ATMOSPHERE WITH COLD AIR ALOFT DURING THE WARM PART 
OF THE DAY.
&&

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

$$

RUNK/JACQUES