Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 211545
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
845 AM PDT SUN SEP 21 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM WILL LIFT FROM CENTRAL CALIFORNIA
ACROSS NORTHERN NEVADA TODAY. DRIER AIR WILL GRADUALLY SPREAD FROM
SOUTHWEST TO NORTHEAST THROUGH THE DAY CAUSING SHOWERS AND
THUNDERSTORMS TO DISSIPATE OVER THE SOUTHERN SIERRA...THE SOUTHERN
GREAT BASIN AND NORTHWEST ARIZONA BY THIS EVENING. DRY CONDITIONS
AND ABOVE NORMAL TEMPERATURES CAN BE EXPECTED THE FIRST HALF OF THE
COMING WEEK FOLLOWED BY A SIGNIFICANT COOLING TREND GOING INTO THE
WEEKEND.
&&

.UPDATE...
AN AIRCRAFT SOUNDING AT 1445Z INTO MCCARRAN IS AN EXTREMELY CLOSE
MATCH WITH THE NAM12 FORECAST SOUNDING FOR 15Z. LOOKING AT THE NAM12
TRENDS AS WELL AS THE LATEST TRENDS IN THE RAP AND HRRR...THE
FORECAST APPEARS TO BE IN GOOD SHAPE THIS MORNING. EXPECT THE
MAJORITY OF THE ACTIVITY TODAY TO BE ACROSS LINCOLN AND NORTHERN
MOHAVE. WE CAN STILL SEE SOME DEVELOPMENT ACROSS NORTHERN
CLARK...NYE...ESMERALDA...AND THE SIERRA THROUGH THE AFTERNOON
BEFORE DRYING OUT. THE LATEST RAP...HRRR...AND 4KM NAM SHOW OUR
FORECAST AREA DRYING OUT QUITE RAPIDLY AS WE HEAD INTO THE EARLY
EVENING HOURS. SO WE MIGHT NOT HAVE MUCH ACTIVITY...EVEN IN LINCOLN
COUNTY...BY ABOUT 5 PM OR SO.
&&

.PREVIOUS DISCUSSION...
408 AM PDT SUN SEP 21 2014

.SHORT TERM...THROUGH TUESDAY NIGHT...RECENT SATELLITE LOOPS SHOWED
THE CENTER OF THE UPPER LOW OVER CENTRAL CALIFORNIA AT 10Z AND THE
SYSTEM WAS PROGRESSIVELY LIFTING TO THE NORTHEAST. CONVECTION ALONG
THE EAST-SOUTHEAST PORTION OF THE SYSTEM WILL CONTINUE TO MOVE UP
ACROSS LINCOLN...NORTHEAST CLARK AND NORTHERN MOHAVE COUNTY THIS
MORNING WHILE DRIER SOUTHWEST SPREADING ACROSS THE REST OF CLARK
COUNTY AND AREAS TO THE WEST SOUTH SHOULD SHUT DOWN THE CONVECTIVE
POTENTIAL AND THE MENTION OF SHOWERS AND THUNDERSTORMS WAS REMOVED.
WE SHOULD STILL SEE A FEW SHOWERS AND THUNDERSTORMS OVER NORTHERN
INYO...ESMERALDA AND CENTRAL NYE COUNTIES AS THESE ZONES WILL BE
NEAR THE CENTER OF THE CLOSED LOW. DRY SOUTHWEST TO WESTERLY FLOW
WILL CONTINUE TO SPREAD OVER THE FORECAST AREA TONIGHT AS THE UPPER
LOW LIFTS ACROSS THE NORTHERN INTERMOUNTAIN REGION. THIS WILL
PROVIDE DRY CONDITIONS WITH A WARMING TREND MONDAY AND TUESDAY AS A
RIDGE DEVELOPS OVER THE GREAT BASIN AHEAD OF A DEEP EASTERN PACIFIC
TROUGH.

.LONG TERM...WEDNESDAY THROUGH SATURDAY...THE EASTERN PACIFIC TROUGH
WILL COME INTO PLAY DURING THIS PERIOD THOUGH THE MEDIUM RANGE
MODELS ARE NOT IN GOOD AGREEMENT WITH ITS PROGRESSION AND DEPTH SO
CONFIDENCE IN THE DETAILS IS LOW. HOWEVER...IT IS SAFE TO SAY THAT
THE SYSTEM WILL BRING A SIGNIFICANT COOLING TREND GOING INTO THE
WEEKEND. WEDNESDAY AND THURSDAY SHOULD BE THE WARMEST DAYS OF THE
WEEK AS THE AMPLIFIED RIDGE SHIFTS TO THE EAST AHEAD OF THE DRY
SOUTHWEST FLOW ASSOCIATED WITH THE APPROACHING TROUGH. THIS WILL
STIR UP BREEZY TO LOCALLY WINDY CONDITIONS THURSDAY AFTERNOON
THROUGH FRIDAY AS THE TROUGH AXIS MOVES INLAND ACROSS CALIFORNIA.
THE GFS KEEPS THE SYSTEM MORE OPEN AND PROGRESSIVE WHILE THE ECMWF
CLOSES OFF AND SLOWS UP THE LOW SATURDAY OVER THE GREAT BASIN. IT
ALSO DEPICTS MORE QPF OVER EASTERN NEVADA AND NORTHWEST ARIZONA THAN
THE GFS. POPS WERE RAISED FOR LINCOLN AND MOHAVE COUNTIES SLIGHTLY
SATURDAY TO ADD SOME OF THE ECMWF SOLUTION INFLUENCE. WHILE
CONFIDENCE IN PRECIPITATION IS SOMEWHAT LOW...CONFIDENCE REMAINS
MODERATE TO HIGH THAT THIS WILL USHER IN THE FEEL OF FALL WITH HIGHS
ONLY IN THE 80S TO LOWER 90S ACROSS MUCH OF THE MOJAVE DESERT REGION
WITH LOWS IN THE 50S AND 60S.
&&

.AVIATION...FOR MCCARRAN...A LOW PRESSURE SYSTEM LIFTING ACROSS
NORTHERN NEVADA TODAY WILL BRING DRIER AND MORE STABLE CONDITIONS TO
THE TERMINAL AREA WITH GENERALLY SCATTERED CLOUDS WITH BASES AROUND
10-12 KFT. LIGHT WINDS THIS MORNING WILL BECOME SOUTH-SOUTHEAST THIS
AFTERNOON AROUND 8-10 KTS BEFORE BECOME SOUTHWEST THIS EARLY THIS
EVENING.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...ISOLATED TO SCATTERED THUNDERSTORMS CAN BE EXPECTED
THIS MORNING THROUGH EARLY AFTERNOON IN AN ARC FROM THE SOUTHERN
SIERRA ACROSS CENTRAL NEVADA AND NORTHWEST ARIZONA. DRIER AND MORE
STABLE AIR SPREADING IN FROM THE SOUTHWEST WILL DECREASE COVERAGE OF
SHOWERS AND THUNDERSTORMS FROM SOUTHWEST TO NORTHEAST THIS AFTERNOON
AND EVENING WITH DRY CONDITIONS TONIGHT.
&&

.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.
&&

$$

UPDATE...PADDOCK
PREVIOUS DISCUSSION...ADAIR

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