AREA FORECAST DISCUSSION...CORRECTION TO ISSUANCE TIME
NATIONAL WEATHER SERVICE LAS VEGAS NV
850 PM PDT THU MAY 15 2008

.SYNOPSIS...AS A LOW PRESSURE SYSTEM ACROSS ARIZONA DEPARTS TO THE
EAST TONIGHT WINDS WILL BEGIN TO LESSEN ACROSS SOUTHERN NEVADA AND
THE COLORADO RIVER VALLEY. STRONG HIGH PRESSURE WILL THEN BUILD OVER
THE WESTERN STATES THROUGH THE WEEKEND...RESULTING IN DRY CONDITIONS
AND A WARMING TREND. BY SUNDAY...HIGH TEMPERATURES WILL APPROACH
NEAR RECORD TO RECORD LEVELS AND CONTINUE BOTH MONDAY AND TUESDAY.
&&

.UPDATE...SURFACE PRESSURE GRADIENTS ARE SLOWLY DECREASING AS THE
UPPER LOW OVER ARIZONA/NEW MEXICO SHIFTS SOUTH OVERNIGHT. THE RESULT
HAS BEEN A DECREASE IN WINDS ACROSS THE SOUTHERN PORTION OF THE CWA
THIS EVENING WHICH HAS ALLOWED FOR THE LAKE WIND ADVISORY AND RED
FLAG WARNINGS TO EXPIRE ON TIME THIS EVENING. EXPECT LOCAL GUSTY
WINDS TO CONTINUE OVERNIGHT...BUT OVERALL SPEEDS TO BE ON THE
DECREASE. WE THEN TURN TOWARDS THE STRONG RIDGE WHICH IS EXPECTED TO
MOVE OVER THE DISTRICT OVER THE WEEKEND. CURRENT SHORT TERM FORECAST
ON TRACK WITH THIS SYSTEM. ZONES UPDATED EARLIER TO REMOVE WIND
ADVISORY HEADLINES AND WILL UPDATE AGAIN LATER TO REMOVE
EVENING/MIDNIGHT WORDING...OTHERWISE NO FURTHER UPDATES PLANNED
ATTM.
&&

.AVIATION...FOR MCCARRAN...NORTHEAST WINDS TO SLOWLY SUBSIDE THROUGH
08Z WITH SPEEDS LESS THAN 10KTS AFTER 08Z. NORTHEAST WINDS TO ONCE
AGAIN INCREASE AFT 17Z WITH SPEEDS AROUND 12KTS EXPECTED ON
FRIDAY...BEFORE DECREASING BELOW 10KTS BY 02Z SATURDAY. SKIES TO BE
GENERALLY CLEAR THROUGH THE WEEKEND.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...NORTH TO NORTHEAST WINDS 10-20KTS OVERNIGHT AND INTO
FRIDAY WITH LOCAL GUSTY WINDS ONCE AGAIN ALONG THE THE COLORADO
RIVER VALLEY FRIDAY AFTERNOON. EXPECT GENERALLY LIGHT WINDS AREAWIDE
SATURDAY AFTERNOON. SKIES TO BE GENERALLY CLEAR THROUGH THE WEEKEND.
&&

.PREV DISCUSSION...356 PM PDT SHORT TERM...A TIGHT NORTHERLY SURFACE
PRESSURE GRADIENT ACROSS THE AREA WAS ALLOWING FOR GUSTY WINDS ONCE
AGAIN ACROSS PARTS OF THE AREA TODAY. LATEST ELY-EED GRADIENT WAS AT
11.5 MB...WHICH MODELS STILL DID NOT INITIALIZE STRONG ENOUGH. GFS
HAS BEEN DOING A BETTER JOB GRASPING THE SFC P-GRAD. SO FAR WINDS
HAVE GUSTED AS HIGH AS 38 MPH TODAY AT NELLIS AFB AND WINDS HAVE
REACHED 40 MPH AT THE NEEDLES AIRPORT. THE SURFACE PRESSURE GRADIENT
WILL BECOME MORE NORTHEAST OVERNIGHT AND THEN EASTERLY TOMORROW AS A
SYSTEM OVER ARIZONA PULLS AWAY FROM THE REGION. THIS WILL ALLOW
WINDS TO SUBSIDE OVERNIGHT. LAKE WIND ADVISORY HAS ALREADY
VERIFIED...BUT GIVEN THE EXPECTED RELAXING OF THE GRADIENT THIS
EVENING PLAN TO LET THE ADVISORY EXPIRE WHEN IT IS EXPECTED TO.

DRIER AIR WORKING INTO THE AREA FROM THE NORTH HAS HELPED TO CLEAR
OUT THE CLOUDS AND EXPECT A CLEAR SKY TONIGHT FOR THE MOST PART.
RH PROGS ARE DRY INTO TOMORROW AND SO A SUNNY DAY IS EXPECTED.
HIGHS TOMORROW LOOK TO BE FAIRLY CLOSE TO WHERE WE WIND UP TODAY
AS WE REMAIN IN A NORTHERLY FLOW. HIGH PRESSURE ACROSS THE PAC NW
WILL GRADUALLY BUILD SOUTHWARD THIS WEEKEND. THIS WILL ALLOW FOR A
WARMING TREND TO TAKE PLACE. BY SUNDAY...THE HIGH WILL BUILD
TOWARDS SOUTHERN CALIFORNIA. H7 TEMPS LOOK TO WARM TO BETWEEN +14C
TO +17C ACROSS THE CWFA AND H5 HEIGHTS TO OR ABOVE 588 DM. MODEL
SOUNDINGS SHOW GOOD MIXING TAKE PLACE...AND GIVEN THE ABOVE
PARAMETERS...HIGH TEMPS WILL RISE TO THEIR WARMEST LEVELS OF THE
YEAR. THE FORE CASTED HIGHS ARE WITHIN OR ARE EXPECTED TO BREAK
RECORDS...SEE THE CLIMATE SECTION BELOW. MARGINAL MOISTURE AND
INSTABILITY OVER THE HIGHER PEAKS OF THE SIERRA AND WHITE
MOUNTAINS WILL RESULT IN SOME CUMULUS IN THE AFTERNOON SATURDAY
AND AGAIN ON SUNDAY. OTHERWISE...EXPECT SCORCHING SUNSHINE DURING THE
DAY AND A CLEAR SKY AT NIGHT...THOUGH A LITTLE HIGH LEVEL MOISTURE
MAY RESULT IN A FEW CIRRUS UP NORTH AT TIMES.

.LONG TERM...FORECAST CONFIDENCE RAPIDLY DETERIORATES FROM ABOVE
NORMAL ON MONDAY TO BELOW NORMAL BY THE MIDDLE OF THE WEEK. AS THE
WEEK BEGINS...THE HOT RIDGE WILL REMAIN THE DOMINANT FEATURE.
TEMPERATURES WILL THREATEN RECORD HIGHS AGAIN IN LAS VEGAS ON
MONDAY...AND THERE IS AN OUTSIDE CHANCE OF REACHING EXCESSIVE HEAT
WARNING CRITERIA. STAY TUNED. BY TUESDAY...MODELS AGREE THAT THE
RIDGE WILL BE IN SOME STAGE OF BREAKING DOWN AS A TROUGH MOVES INTO
THE WEST COAST...BUT THERE IS POOR AGREEMENT ON THE TIMING AND
ESPECIALLY THE AMPLITUDE OF THE TROUGH. THE GFS SHOWS A LESS
AMPLIFIED TROUGH TUESDAY EVENTUALLY AMPLIFYING OVER THE
INTERMOUNTAIN WEST AND FORMING A CLOSED LOW WHICH DIGS DOWN INTO
SOUTHERN ARIZONA THURSDAY /NOT MUCH DIFFERENT FROM THE PATTERN
TODAY/. THE ECMWF SHOWS A MUCH MORE AMPLIFIED TROUGH SLAMMING INTO
CALIFORNIA TUESDAY AND A CLOSED LOW CROSSING NEVADA TUESDAY NIGHT.
THIS SEEMS UNLIKELY GIVEN THE SIZE OF THE RIDGE IN PLACE BEFORE THE
SYSTEM REACHES THE COAST...SO LEANED ON THE GFS ENSEMBLE
MEAN...WHICH RESULTED IN MINIMAL CHANGES TO THE PREVIOUS FORECAST.
&&

.CLIMATE...AS MENTIONED ABOVE WITH A SPRAWLING RIDGE OF HIGH
PRESSURE EXPECTED TO PERSIST ACROSS THE REGION THIS WEEKEND INTO
EARLY NEXT WEEK...NEAR RECORD TO RECORD-BREAKING HIGH TEMPERATURES
ARE EXPECTED IN THE CWFA. RECORD HIGH MINIMUM TEMPERATURES ALSO LOOK
POSSIBLE AT LAS VEGAS. BELOW IS A LIST OF RECORDS FOR SEVERAL SITES
IN OUR AREA AS WELL AS SOME STATISTICS ON TRIPLE DIGIT TEMPERATURES
FOR LAS VEGAS.

RECORD HIGHS...

LOCATION       SATURDAY     SUNDAY      MONDAY      TUESDAY
               5/17         5/18        5/19        5/20
---------------------------------------------------------------------
LAS VEGAS      102/1970*    103/1973    102/2006*   102/2005*
BISHOP          97/1954     100/1954     98/1954     96/1984
DAGGETT        103/2006     102/1954    103/2006    103/1984
DEATH VALLEY   116/2006     116/2006    114/2006    114/1947
NEEDLES        110/2006     110/2006    110/2006    109/2005

*INDICATES THE LAST TIME A RECORD HIGH WAS SET.

RECORD HIGH MINIMUMS FOR LAS VEGAS...
5/18...77/2006
5/19...80/2006
5/20...77/2006 AND PREVIOUS YEARS

FOR LAS VEGAS...THE AVERAGE DATE OF THE FIRST TRIPLE DIGIT
TEMPERATURE IS MAY 25TH. THE EARLIEST TRIPLE DIGIT TEMPERATURE WAS
ON MAY 1 1947. THE LATEST OCCURRENCE OF THE FIRST 100 DEGREE OR
BETTER TEMPERATURE WAS JUNE 30 1965.
&&

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