Weather Service Report


008 
FXUS65 KVEF 202145
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
245 PM PDT SAT SEP 20 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM CIRCULATING NEAR THE SOUTHERN 
CALIFORNIA COAST WILL PULL MOISTURE ACROSS SOUTHERN NEVADA AND 
NORTHWEST ARIZONA THROUGH SUNDAY LEADING TO SCATTERED TO NUMEROUS 
SHOWERS AND THUNDERSTORMS. THE SYSTEM WILL LIFT AWAY TO THE 
NORTHEAST BY LATE SUNDAY FOLLOWED BY DRY CONDITIONS AND ABOVE NORMAL 
TEMPERATURES THROUGH THE FIRST HALF OF NEXT WEEK. 
&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
THE UPPER LOW WE HAVE BEEN WATCHING THE LAST FEW DAYS OVER THE 
WESTERN CALIFORNIA COAST IS STARTING TO MOVE NORTHEAST AND WILL 
CONTROL OUR WEATHER THROUGH SUNDAY. THIS WILL PROVIDE SHOWER AND 
THUNDERSTORM CHANCES AS WELL AS COOLER TEMPERATURES. DRY CONDITIONS 
AND A WARMING TREND WILL COMMENCE MONDAY.

MOISTURE CONTINUES TO INCREASE ACROSS OUR AREA...WRAPPING 
CYCLONICALLY AROUND THE UPPER LOW TO OUR WEST. SCATTERED SHOWERS AND 
THUNDERSTORMS HAVE BEEN AROUND THROUGHOUT THE DAY AND WILL INCREASE 
IN COVERAGE THROUGH THIS EVENING. AREA PW VALUES RANGING FROM 1 INCH 
IN OUR NORTHWEST TO 1.5 INCHES ALONG THE COLORADO RIVER NEAR NEEDLES 
ARE FORECAST BY EARLY EVENING...WHICH WOULD PROMOTE HEAVY RAIN. AREA 
AVERAGE RAIN AMOUNTS OF 0.25-0.50 INCHES WITH LOCALIZED AMOUNTS OVER 
1 INCH WILL BE POSSIBLE. THE AVERAGE STORM MOTION WILL BE AROUND 20 
MPH OR SO...WITH STORMS MOVING FROM SOUTHEAST TO NORTHWEST. THIS 
MOTION WOULD GENERALLY LIMIT THE AMOUNT OF TIME ANY ONE CELL IS OVER 
ONE PARTICULAR AREA. HOWEVER...THERE CAN BE SOME ISOLATED AREAS 
WHERE REDEVELOPMENT OR TRAINING CONVECTION FOR A SHORT PERIOD OF 
TIME MAY WARRANT THE ISSUANCE OF A FLASH FLOOD WARNING HERE AND 
THERE. WITH WIDESPREAD FLASH FLOODING NOT ANTICIPATED AT THIS 
TIME...WILL NOT ISSUE ANY WATCH PRODUCTS BUT TRENDS WILL BE 
MONITORED. THE STRONGEST STORMS MAY ALSO PRODUCE SOME GUSTY WINDS IN 
EXCESS OF 45 MPH AS WELL AS SOME HAIL. SO PLEASE KEEP ALERT OF 
CHANGING WEATHER CONDITIONS THIS AFTERNOON AND EVENING PARTICULARLY 
IF YOU HAVE OUTDOOR PLANS.

THE LOW WILL CONTINUE A NORTHEAST TRACK ACROSS CALIFORNIA AND NEVADA 
TONIGHT AND SUNDAY. THE FOCUS FOR CONVECTION WILL SHIFT NORTH...WITH 
DRIER AIR WORKING INTO OUR CALIFORNIA AREAS LATE TONIGHT AND 
ESPECIALLY BY SUNDAY AFTERNOON. SO...SHOWER AND THUNDERSTORM CHANCES 
WILL BE MAINLY CONFINED TO SOUTHERN NEVADA AND NORTHWEST ARIZONA 
SUNDAY. THE LOW WILL EXIT THE REGION BY SUNDAY NIGHT WITH DRY AIR 
PUSHING ACROSS THE REST OF THE AREA OVERNIGHT...BRINGING AN END TO 
SHOWER AND STORM CHANCES. 

.LONG TERM...TUESDAY AND WEDNESDAY. HIGH PRESSURE EXPANDS OVER THE 
AREA IN RESPONSE TO A DEEPENING PACIFIC TROUGH OFF THE WEST COAST. 
OVERALL, DRY AND MOSTLY CLEAR CONDITIONS ALONG WITH LIGHT WINDS ARE 
EXPECTED. TEMPERATURES ARE FORECAST TO BE 4-8 DEGREES ABOVE NORMAL.

WEDNESDAY THROUGH SATURDAY...CONTINUED TRENDING THE FORECAST WITH 
THE MORE CONSISTENT GFS DURING THIS PERIOD BUT DID NOT COMPLETELY 
RULE OUT THE ECMWF GIVEN ITS AGREEMENT WITH THE GFS REGARDING A  
CLOSED LOW MOVING OVER THE GREAT BASIN. THE GFS BRINGS A SHARP 
SHORTWAVE AROUND THE BASE OF A PACIFIC TROUGH AND INTO NORTHERN AND 
CENTRAL CALIFORNIA THURSDAY. THIS WOULD RESULT IN BREEZY TO LOCALLY 
WINDY CONDITIONS ACROSS THE AREA WITH POSSIBLE WEAK DOWNSLOPE FLOW 
OCCURRING ALONG THE EASTERN SIERRA SLOPES. THE GFS SOLUTION LIFTS 
THE SHORTWAVE QUICKLY TO THE NORTHEAST WITH THE MAIN TROUGH AXIS 
THEN PUSHING INTO CALIFORNIA AND NEVADA FRIDAY. IF THE GFS IS 
CORRECT, THERE COULD BE A PERIOD OF STRONG WINDS ACROSS PORTIONS OF 
THE AREA FRIDAY WITH WARM TEMPERATURES AGAIN OVER THE DESERTS BUT 
COOLING CONDITIONS OVER INYO COUNTY AND THE SOUTHERN GREAT BASIN. 
COOLER WEATHER WOULD THEN BE IN STORE FOR THE BEGINNING OF THE 
WEEKEND WITH TEMPERATURES POTENTIALLY WELL BELOW NORMAL FOR LATE 
SEPTEMBER. THE ECMWF IS MUCH WETTER THAN THE GFS ON SATURDAY DUE TO 
THE LOCATION OF THE LOW SO THE OFFICIAL FORECAST TAKES THIS INTO 
ACCOUNT WITH A SLIGHT CHANCE OF SHOWERS IN THE FAVORED REGIONS OF 
THE LOW WHICH INCLUDES PORTIONS OF THE SIERRA, THE NORTHERN CWA AND 
MOHAVE COUNTY. 
&&

.AVIATION...FOR MCCARRAN...MOISTURE CONTINUES TO INCREASE LEADING TO 
SCATTERED SHOWERS AND THUNDERSTORMS OVER SOUTHERN NEVADA THIS 
AFTERNOON THROUGH TONIGHT. PREVAILING WINDS WILL BE SOUTH-SOUTHEAST 
AROUND 5-8 KTS THIS AFTERNOON AND EARLY EVENING BUT GUSTY AND 
ERRATIC WINDS CAN BE EXPECTED THROUGH THE EVENING DUE TO SHOWERS AND 
THUNDERSTORMS NEAR THE TERMINAL AREA. STORM COVERAGE WILL BE MOST 
EXTENSIVE IN BEATTY...PEACH SPRINGS...AND MORMON MESA CORRIDORS. 
BKN-OVC CLOUDS WILL GENERALLY HAVE BASES 8-10 KFT BUT WILL LIKELY 
LOWER TO AROUND 6 KFT NEAR ANY SHOWERS AND THUNDERSTORMS. A CLEARING 
TREND WILL OCCUR SUNDAY.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST 
CALIFORNIA...MOISTURE CONTINUES TO INCREASE OVER MUCH OF SOUTHERN 
NEVADA AND NORTHWEST ARIZONA WITH SCATTERED TO NUMEROUS SHOWERS AND 
THUNDERSTORMS EXPECTED THROUGH TONIGHT. LOWERING CLOUDS BASES WILL 
LEAD TO MARGINAL VFR CONDITIONS OVER SOUTH CENTRAL NEVADA AND 
NORTHWEST ARIZONA WITH MOUNTAIN OBSCUREMENT LIKELY. A CLEARING TREND 
WILL OCCUR FROM SOUTHWEST TO NORTHEAST SUNDAY. 
&&

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME. HOWEVER....SPOTTERS 
ARE ENCOURAGED TO REPORT ANY SIGNIFICANT WEATHER CONDITIONS 
ACCORDING TO STANDARD OPERATING PROCEDURES.
&&

$$

SHORT TERM/AVIATION...PADDOCK
LONG TERM...SALMEN

FOR MORE FORECAST INFORMATION...SEE US ON OUR WEBPAGE:

HTTP://WEATHER.GOV/LASVEGAS OR FOLLOW US ON FACEBOOK AND TWITTER



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