Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 050418 AAA
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
917 PM PDT MON MAY 4 2015

.SYNOPSIS...SHOWERS AND THUNDERSTORMS REMAIN POSSIBLE THIS AFTERNOON
BEFORE SLOWLY WINDING DOWN OVERNIGHT. LESS SHOWER AND STORM COVERAGE
IS EXPECTED TUESDAY AND WEDNESDAY WITH GREATEST CHANCES ACROSS THE
MOUNTAINS OF INYO COUNTY AND THE SOUTHERN GREAT BASIN. ANOTHER LOW
PRESSURE SYSTEM WILL BRING MORE UNSETTLED WEATHER AND MUCH COOLER
CONDITIONS TO THE REGION THURSDAY AND FRIDAY.
&&

.UPDATE...IR IMAGERY SHOWS THE UPPER LOW CENTER OVER CENTRAL ARIZONA
WITH WRAPAROUND MOISTURE ON THE BACKSIDE OF THE SYSTEM SPREADING
ACROSS MUCH OF THE FORECAST AREA. THE EXCEPTION WOULD BE MOSTLY
CLEAR CONDITIONS ON THE FAR WESTERN CWA FRINGES. ALTHOUGH SOME
HEAVIER THUNDERSTORM SHOWERS WERE SEEN EARLIER TODAY, ONLY WIDELY
SCATTERED LIGHT SHOWER ACTIVITY REMAINS AS OF 9 PM. MODELS CONTINUE
TO FOCUS THE BEST CHANCE OF PRECIPITATION OVER THE EASTERN HALF OF
THE CWA INCLUDING LINCOLN, CLARK, EASTERN SAN BERNARDINO AND MOHAVE
COUNTIES. AS THE LOW SLOWLY EDGES EASTWARD OVERNIGHT, THE CHANCE FOR
SHOWERS ERODE IN CENTRAL AREAS...LEAVING THE EASTERN PORTIONS OF THE
AREA (MAINLY MOHAVE COUNTY) WITH THE BEST CHANCES AFTER MIDNIGHT.
GRIDS WERE TWEAKED AND THE EVENING UPDATE IS OUT. &&

.AVIATION...FOR MCCARRAN...BARRING ANY MORE SHOWER ACTIVITY, WINDS
ARE EXPECTED TO FAVOR A SOUTHWEST DIRECTION THROUGH THE NIGHT. CIGS
WILL GENERALLY BE AOA 12K FEET OVERNIGHT.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...LIGHT TO MODERATE SHOWERS AND ISOLATED THUNDERSTORMS
ARE POSSIBLE THROUGH THE NIGHT WITH THE BEST CHANCE IN LINCOLN,
CLARK, EASTERN SAN BERN AND MOHAVE COUNTIES. CIGS GENERALLY 10-12K
FEET EXCEPT 7-9K FEET IN SHOWER ACTIVITY. SHOWERS WILL SLOWLY
DIMINISH FROM WEST TO EAST TONIGHT AS LOW PRESSURE SYSTEM DEPARTS.
&&

.PREVIOUS DISCUSSION...315 PM PDT...

.SHORT TERM...THROUGH TUESDAY NIGHT

ACTIVE AFTERNOON TODAY WITH WIDESPREAD SHOWERS AND THUNDERSTORMS
OCCURRING AS A SOUTHERN STREAM CLOSED LOW MOVES ACROSS THE DESERT
SOUTHWEST.  FORECAST GUIDANCE SUPPORTS THIS ACTIVITY CONTINUING
THROUGH THE EARLY EVENING HOURS SUPPORTED BY A DIFFLUENT FLOW ALOFT
ON THE NORTHEAST QUADRANT OF THE LOW.  GREATEST CHANCES OF STORMS
LOOK TO IMPACT SOUTHERN CLARK...MOHAVE AND FAR EASTERN SAN
BERNARDINO COUNTIES THIS EVENING.   THIS LOW WILL SLOWLY PUSH EAST
TONIGHT TAKING THE ENHANCED CHANCES FOR SHOWERS AND THUNDERSTORMS
EASTWARD WITH IT.

MUCH DRIER CONDITIONS ARE EXPECTED TUESDAY BUT SOME SHOWERS AND
ISOLATED THUNDERSTORMS WILL REMAIN POSSIBLE ACROSS THE SOUTHERN
GREAT BASIN AND EASTERN MOHAVE COUNTY WHERE RESIDUAL INSTABILITY
WILL BE IN PLACE AND MAY SUPPORT SOME ADDITIONAL ACTIVITY.
TEMPERATURES WILL BE NEAR SEASONAL AVERAGES.

.LONG TERM....WEDNESDAY MORNING THROUGH MONDAY.

SUBTLE SHORTWAVE RIDGE IN THE WAKE OF THE FIRST SOUTHERN STREAM
SHORTWAVE WILL MOVE OFF TO THE EAST...GIVING WAY TO YET ANOTHER
SHORTWAVE EMBEDDED IN THE SOUTHERN BRANCH OF THE JET. THIS...COUPLED
WITH INFLUENCES FROM A SIGNIFICANT TROUGH BEGINNING TO DIG SOUTHWARD
ACROSS CENTRAL CALIFORNIA AND LINGERING MOISTURE FROM THE FIRST
SYSTEM WILL KEEP CHANCES FOR SHOWERS AND STORMS IN THE FORECAST FOR
WEDNESDAY AFTERNOON...MAINLY ACROSS NORTHERN INYO AND THE SOUTHERN
GREAT BASIN ZONES AS THE BEST UPPER LEVEL SUPPORT AND INSTABILITY
WILL BE PRESENT HERE. POPS WILL AGAIN BE THE HIGHEST THESE AREAS ON
THURSDAY...AS THE MID/UPPER LEVEL LOW CONTINUES TO DIG SOUTHWARD
OVER CENTRAL CALIFORNIA AND STRENGTHEN...WITH CURRENT OPERATIONAL
MODEL GUIDANCE DEPICTING A ~550 DM CLOSED LOW THURSDAY AFTERNOON
INTO FRIDAY. GOOD MODEL AGREEMENT CONTINUES THIS AFTERNOON IN
KEEPING THE DEEPEST MOISTURE AND BEST INSTABILITY UNDER THE UPPER
LOW...WITH A DRY SLOT DEVELOPING TO THE EAST OF THE LOW ON LATE
THURSDAY/FRIDAY...INHIBITING PRECIPITATION CHANCES ACROSS SAN
BERNARDINO...CLARK...LINCOLN...AND MOHAVE COUNTIES. LITTLE CHANGES
WERE MADE TO POPS ON THURSDAY AND EARLY FRIDAY AS A RESULT.

CONFIDENCE CONTINUES TO INCREASE IN FRIDAY BEING THE MOST ACTIVE DAY
AREA-WIDE...AS THE JET STREAK ROUNDS THE BASE OF THE TROUGH AND
BEGINS TO EJECT THE MID/UPPER LOW OUT OF CALIFORNIA. EXPECT
WIDESPREAD SHOWERS WITH EMBEDDED THUNDERSTORMS...AS 500MB CHARTS
CONTINUE TO INDICATE TEMPS RANGING FROM -25C TO -30C AT THE CORE OF
THE LOW AS IT TRACKS OVER THE SOUTHERN GREAT BASIN. IT IS NOTED THAT
THE 12Z MODEL GUIDANCE DIGS THE LOW A LITTLE FURTHER SOUTH THAN
YESTERDAYS 00Z RUNS...WHICH WOULD INCREASE THE AMOUNT OF AVAILABLE
MOISTURE SOUTH OF THE I-40 CORRIDOR ON FRIDAY. OPTED NOT TO MAKE ANY
SIGNIFICANT CHANGES AT THIS TIME...AS ANOTHER 1-2 RUNS OF
CONSISTENCY WITH MODEL GUIDANCE IN THE FORECAST LOW TRACK WOULD
BETTER JUSTIFY RAISING POPS IN THIS AREA.

THE MID/UPPER LEVEL LOW WILL EJECT OFF TO THE EAST ON SATURDAY...BUT
LINGERING UPPER LEVEL ENERGY COUPLED WITH MOISTURE ON THE BACKSIDE
OF THE LOW WILL KEEP SHOWERS AND THUNDERSTORMS A POSSIBILITY ACROSS
MAINLY CENTRAL AND EASTERN PORTIONS OF THE CWA ON SATURDAY...WITH
ACTIVITY TAPERING OFF FROM WEST TO EAST THROUGHOUT THE DAY. FLOW
WILL TRANSITION TO WESTERLY ON SUNDAY AND EVENTUALLY SOUTHWESTERLY
ON MONDAY...YIELDING QUIET WEATHER WITH THE EXCEPTION OF POTENTIAL
BREEZY CONDITIONS AT THE END OF THE PERIOD.

TEMPERATURES WILL DEPART NORMAL VALUES ON THURSDAY...WITH VALUES
FALLING TO AS LOW AS 10-15 DEGREES BELOW NORMAL FOR EARLY MAY ON
FRIDAY...WITH HIGHS IN THE UPPER 60S POSSIBLE FOR LAS VEGAS.
TEMPERATURES WILL QUICKLY REBOUND 5-7 DEGREES FOR SATURDAY BEFORE
RETURNING TO AND EVENTUALLY ABOVE NORMAL AGAIN BY THE END OF THE
WEEKEND AND INTO EARLY NEXT WEEK.
&&


.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/AVIATION...SALMEN
PREV SHORT TERM...OUTLER
PREV LONG TERM...PULLIN

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