Severe Thunderstorm Warning 34, NWS Las Vegas, NV

AREA FORECAST DISCUSSION UPDATA
NATIONAL WEATHER SERVICE LAS VEGAS NV
945 AM PDT SUN OCT 3 2010

.SYNOPSIS...ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL
CONTINUE ACROSS THE REGION TODAY AS A LOW PRESSURE SYSTEM OVER THE
CALIFORNIA COASTAL WATERS SLOWLY MOVES INLAND. A DRAMATIC CHANGE IN
THE WEATHER PATTERN WILL OCCUR EARLY NEXT WEEK...AS A MUCH COLDER
SYSTEM DIVES INTO THE REGION BY TUESDAY. TEMPERATURES WILL BE 15 TO
20 DEGREES BELOW NORMAL AND SHOWERY WEATHER WILL BRING A CHANCE OF
SNOW TO THE MOUNTAINS.
&&

.UPDATE...OVER THE MAJORITY OF THE FORECAST AREA CONDITIONS REMAIN
QUIET THIS MORNING...EXCEPT FOR ALONG THE COLORADO RIVER VALLEY
ZONES WHERE CONVECTION IS ONCE AGAIN FOCUSED. A GROUP OF STORMS THAT
RECENTLY ROLLED THROUGH BULLHEAD CITY/LAUGHLIN AND PRODUCED MODERATE
TO HEAVY RAIN IS NOW MOVING ACROSS THE LAKE MEAD NATIONAL
RECREATIONAL AREA. ANOTHER CLUSTER JUST SOUTH OF LAUGHLIN IS
FOLLOWING QUICKLY BEHIND...AND THIS CLUSTER IS EXPECTED TO HOLD
TOGETHER....WITH RADAR INDICATING APPROXIMATELY 50KTS AT 10KFT
HELPING TO SUSTAIN CONVECTION. THIS CLUSTER IS SHOWING THE BEST
ORGANIZATION OF THE WEEKEND SO FAR ACROSS THE FORECAST AREA AND WILL
NEED TO MONITOR CLOSELY FOR POTENTIAL SEVERE WEATHER CONDITIONS.
WILL ALSO NEED TO KEEP CLOSE WATCH ON RAINFALL AMOUNTS FROM ANY NEW
STORMS PASSING OVER THE LAKE MEAD NRA...WITH MOST BASINS ALREADY AT
50% OF THE RAINFALL TYPICALLY NEEDED BEFORE WE START TO AT LEAST SEE
MINOR FLOODING. FOR THIS AFTERNOON...LIS ARE PROGGED TO BE AS HIGH
AS -4 ACROSS SAN BERNARDINO COUNTY...WITH ABOUT -2 BEING THE AVERAGE
ACROSS THE AREA TODAY...AND THE CURRENT FORECAST LOOKS ON TRACK WITH
MODELS CONTINUING TO SHOW MORE WIDESPREAD CONVECTION DEVELOPING
ACROSS THE FORECAST AREA. -KENENDY-
&&

.PREV DISCUSSION...
248 AM PDT SUN OCT 3 2010

.SHORT TERM...THUNDERSTORMS ARE ONGOING AGAIN THIS MORNING IN THE
SOUTHEAST QUARTER OF THE CWFA...AND SHOULD SPREAD/DEVELOP FARTHER
NORTH AS THE DAY GOES ON AND THE LOW NEAR THE SOUTHERN CALIFORNIA
COAST SLOWLY LIFTS NORTHEAST. AS THE NORTHERN STREAM LOW DIVES DOWN
MONDAY AND TAKES UP RESIDENCE OVER OUR CWFA TUESDAY...THE FOCUS
SHIFTS TO THE NORTHERN CWFA IN THE AREA OF BEST DYNAMICS AND
INSTABILITY. CONFIDENCE IN THE DETAILS IS LOW...BECAUSE A SMALL
DIFFERENCE IN THE EXACT TRACK OF THE LOW COULD MAKE A BIG DIFFERENCE
IN THE SENSIBLE WEATHER IN ANY ONE PLACE /E.G. DOES LAS VEGAS END UP
DIRECTLY UNDER THE COLD CORE OR IN THE RELATIVELY WARM SOUTHERLY
FETCH JUST EAST OF THE CENTER/. CURRENT FORECAST REPRESENTS A BLEND
OF THE GUIDANCE. TEMPERATURES WILL BE COOLER TODAY...COOLER STILL ON
MONDAY...AND TUESDAY WILL LIKELY BE THE COOLEST DAY WITH HIGHS IN
LAS VEGAS ONLY IN THE LOWER 70S...A 30 DEGREE DROP FROM THE WEEK
BEFORE.

.LONG TERM...LITTLE CHANGE TO THE ONGOING FORECAST AS A DEEP LOW
PRESSURE SYSTEM DROPS OVER THE AREA THROUGH MUCH OF THE EXTENDED
PERIOD. IT LOOKS LIKE THE GREATEST CHANCE OF PRECIPITATION WILL BE
ACROSS THE NORTHERN HALF OF THE CWA...BUT MOST AREAS OF THE FORECAST
AREA WILL SEE AT LEAST A CHANCE. THERE WILL ALSO BE ENOUGH COLD AIR
TO BRING SNOW LEVELS DOWN TO AROUND 7500 FEET. MODELS BEGIN TO
DIFFER LATE IN THE WEEK AS THE LOW IS FORECAST TO SHIFT NORTHEAST.
THE GFS LIFTS THE LOW TO THE NORTHEAST AS A RIDGE BUILDS OVER THE
WEST COAST AND EVENTUALLY BRINGS MUCH WARMER TEMPERATURES BACK INTO
THE FORECAST. THE ECMWF ALSO SHOWS THE LOW LIFTING NORTHEAST...BUT
EVENTUALLY PINCHES ANOTHER CLOSED LOW OFF THE ORIGINAL LOW AND
RECENTERS IT OVER THE FORECAST AREA BY NEXT WEEKEND. RIGHT NOW AM
GOING TO BASE THE FORECAST ON THE GFS SOLUTION AND SHOW A GRADUAL
DRYING AND WARMING TREND LATE IN THE PERIOD.
&&

.AVIATION...FOR MCCARRAN...THE UNSETTLED WEATHER PATTERN WILL
REMAIN ACROSS THE REGION THIS WEEKEND AND MOST OF NEXT WEEK...AS LOW
PRESSURE CURRENTLY SITTING OFF THE SOUTHERN CALIFORNIA COAST MOVES
OVER THE AREA AND QUICKLY GETS REPLACED BY A DEEP UPPER LOW TO
SETTLE OVER THE SOUTHERN GREAT BASIN NEXT WEEK. THERE WILL BE
ISOLATED SHOWERS AND THUNDERSTORMS TODAY THROUGH TUESDAY WITH SOME
STORMS PRODUCING BRIEF HEAVY RAIN AND GUSTY WINDS. BEST CHANCE OF
SEEING WIDESPREAD RAIN SHOWERS WILL BE MONDAY.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...UNSETTLED WEATHER WILL PERSIST OVER THE NEXT SEVERAL
DAYS AS AN AREA OF LOW PRESSURE CONTINUES TO SPIN OFF THE SOUTHERN
CALIFORNIA COAST. GUSTY WINDS AND CIGS AROUND 5KFT WILL BE POSSIBLE
IN AND NEAR ANY SHRA/TSRA ACTIVITY...WITH SCT-BKN CLOUDS AOA
10K FEET ELSEWHERE. THIS UNSETTLED WEATHER PATTERN WILL REMAIN IN
PLACE THROUGH MUCH OF NEXT WEEK.
&&

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

MORGAN/GORELOW

HTTP://WEATHER.GOV/LASVEGAS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LAS VEGAS NV
226 AM PDT SUN OCT 3 2010

AZZ001>003-036-CAZ519>527-NVZ014>022-040700-
NORTHWEST PLATEAU-LOWER COLORADO RIVER VALLEY-NORTHWEST DESERTS-
LAKE MEAD NATIONAL RECREATION AREA-EASTERN SIERRA SLOPES-
OWENS VALLEY-WHITE MOUNTAINS OF INYO COUNTY-
DEATH VALLEY NATIONAL PARK-WESTERN MOJAVE DESERT-
EASTERN MOJAVE DESERT-MORONGO BASIN-CADIZ BASIN-
SAN BERNARDINO COUNTY-UPPER COLORADO RIVER VALLEY-
ESMERALDA AND CENTRAL NYE COUNTY-LINCOLN COUNTY-
NORTHEAST CLARK COUNTY-WESTERN CLARK AND SOUTHERN NYE COUNTY-
SHEEP RANGE-SPRING MOUNTAINS-LAS VEGAS VALLEY-
SOUTHERN CLARK COUNTY-
226 AM PDT SUN OCT 3 2010 /226 AM MST SUN OCT 3 2010/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHWEST
ARIZONA...CALIFORNIA AND SOUTHERN NEVADA.

.DAY ONE...TODAY AND TONIGHT

ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED AGAIN TODAY AND
TONIGHT. SEVERE WEATHER AND FLASH FLOODING ARE NOT LIKELY...BUT
ISOLATED OCCURRENCES CANNOT BE RULED OUT.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

CHANCES FOR SHOWERS AND THUNDERSTORMS WILL CONTINUE AT LEAST
THROUGH THURSDAY. MUCH COOLER AIR WILL ARRIVE TUESDAY AND STAY IN
PLACE THROUGH SATURDAY...POTENTIALLY LEADING TO SNOW IN THE HIGHER
MOUNTAINS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED. HOWEVER...SPOTTERS ARE
ENCOURAGED TO REPORT ANY SIGNIFICANT WEATHER CONDITIONS ACCORDING
TO STANDARD OPERATING PROCEDURES.

MORGAN