Flash Flood Warning 42, NWS Las Vegas, NV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
256 PM PDT THU AUG 30 2007

.SYNOPSIS...A WEAK DISTURBANCE WILL ACT ON PLENTIFUL LOW LEVEL
MOISTURE TO PRODUCE SCATTERED SHOWERS AND THUNDERSTORMS OVER PARTS
OF THE MOJAVE DESERT AND SOUTHERN GREAT BASIN THIS EVENING...MAINLY
ALONG AND EAST OF HIGHWAY 93. UPPER LEVEL HIGH PRESSURE WILL BUILD
OVERHEAD FROM THE EAST BEGINNING ON FRIDAY...WHICH WILL LIMIT
THUNDERSTORM CHANCES TO THE HIGHER TERRAIN IN THE AFTERNOONS AND
EVENINGS THROUGH THE HOLIDAY WEEKEND. TEMPERATURES WILL BE SEVERAL
DEGREES ABOVE NORMAL...AND HUMID CONDITIONS WILL PERSIST THROUGH THE
WEEKEND.
&&

.SHORT TERM...INTERESTING DAY TODAY. A WEAK SHORTWAVE TROUGH
ROTATING IN FROM THE PACIFIC IGNITED SHOWERS AND THUNDERSTORMS OVER
CALIFORNIA DURING THE PREDAWN HOURS. AS THE DAY WORE ON...THESE
STORMS DRIFTED NORTHEAST AND WEAKENED. THIS AFTERNOON...NEW STORMS
HAVE FIRED FARTHER EAST IN AREAS WHICH RECEIVED LOTS OF SUNSHINE
TODAY. A COUPLE OF THESE STORMS HAVE PRODUCED LOCALLY EXCESSIVE
RAIN. AS THE SHORTWAVE MOVES OUT TONIGHT...AND SOLAR HEATING IS
LOST...THE STORMS SHOULD DIE OFF. BY TOMORROW...HEIGHTS AND MID
LEVEL TEMPERATURES RISE A BIT MORE AS THE MID LEVEL RIDGE BUILDS IN
FROM THE EAST. THIS SHOULD PUT A LID ON MOST CONVECTION...LIMITING
IT TO OROGRAPHICALLY FAVORED AREAS OVER THE WEEKEND. THERE IS A
CHANCE OF A RIM SHOT ON SATURDAY AND SUNDAY AFTERNOONS...WHICH IS
WHEN CONVECTION ORGANIZES OVER THE MOGOLLON RIM AND ROLLS INTO
MOHAVE COUNTY ON EAST/NORTHEAST FLOW ALOFT. PAINTED SLIGHTLY HIGHER
POPS THERE EACH DAY. THE OTHER PROBLEM WILL BE THE HEAT AND
HUMIDITY. TEMPERATURES WILL BE QUITE CLOSE TO LOCALLY DEVELOPED
EXCESSIVE HEAT WARNING CRITERIA...AND THE HUMID CONDITIONS WILL ALSO
BE TAXING TO THOSE OUTDOORS OVER THE HOLIDAY WEEKEND. STRESSED THIS
IN THE HAZARDOUS WEATHER OUTLOOK FOR NOW...AND WILL KEEP A CLOSE EYE
ON IT TOMORROW.

.LONG TERM...MODELS REMAIN IN FAIR TO POOR AGREEMENT FOR THE
EXTENDED PORTION OF THE FORECAST. ALL MEMBERS DO SHOW SOME TYPE OF
TROUGH DEVELOPING OVER THE NORTHWESTERN CONUS LATE MONDAY.
HOWEVER...THERE IS LITTLE AGREEMENT AS TO HOW FAR SOUTH IT WILL BE
ABLE TO PROGRESS. GFS/DGEX PREFER A VERY STEEP TROUGH EXTENDING INTO
NEVADA WHILE THE EURO/CANADIAN SOLUTIONS HAVE IT MUCH FLATTER WHICH
KEEPS IT WELL TO THE NORTH. AT THE SAME TIME...THERE IS A
POSSIBILITY OF A TROPICAL SYSTEM MOVING INTO THE SOUTHWESTERN CONUS
TOWARD THE END OF NEXT WEEK. LATEST ADVISORY FROM NHC SHOWS TROPICAL
DEPRESSION ELEVEN E POSSIBLY INTENSIFYING TO A HURRICANE BY THE
FIRST PART OF NEXT WEEK AND POSSIBLY TRACKING TOWARD THE SOUTHERN
TIP OF BAJA BY TUESDAY MORNING. HOW FAR IT MAKES IT WILL BE GREATLY
BE DETERMINED IF IT IS ABLE TO INTERACT WITH THE TROUGH OVER THE
WESTERN CONUS. IF THE CANADIAN/EURO THINKING WORKS...THE TROUGH
WOULD LIKELY BE TOO WEAK AND TOO FAR NORTH TO HELP PULL UP THE
DISTURBANCE AND MOISTURE WILL BE MUCH LESS.  GFS SHOWS VERY HIGH PW
VALUES OVER OVER 3 INCHES WITH THIS SYSTEM AND EVEN PUTS VERY HIGH
QPF AMOUNTS ACROSS THE SOUTHERN HALF OF THE CWA BY THURSDAY OF NEXT
WEEK. DUE TO UNCERTAINTY IN BOTH THE TROUGH AND THE TROPICAL
SYSTEM...DECIDED TO ONLY GO WITH SLIGHT CHANCE POPS IN LOCATIONS
EXCEPT FOR THE FAR SOUTHERN MOUNTAINS WHERE 30 POPS WERE INTRODUCED.
PERSONS SHOULD KEEP AN EYE OUT FOR THIS STORM AS THE END OF NEXT
WEEK COULD GET VERY INTERESTING.
&&

.AVIATION...FOR MCCARRAN...SCT TO BKN SKIES WITH ISOLATED TO
SCATTERED SHOWERS AND THUNDERSTORMS THROUGH 03Z ALONG ALL CORRIDORS
AND LOCATIONS. WINDS WILL GENERALLY BE SOUTH TO SOUTHWEST UP TO 12
KT. GUSTS TO 20 KT ARE POSSIBLY THROUGH 03Z DUE TO NEARBY STORMS.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...SCT TO BKN SKIES WITH ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS EXPECTED THROUGH 03Z FOR ALL PLACES NORTH OF NEEDLES.
WINDS WILL GENERALLY BE UNDER 12 KT EXCEPT IN THE VICINITY OF STORMS.
&&

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

MORGAN/BELL

HTTP://WEATHER.GOV/LASVEGAS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LAS VEGAS NV
118 PM PDT THU AUG 30 2007

AZZ001>003-036-CAZ519>527-NVZ014>022-310700-
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-
118 PM PDT THU AUG 30 2007 /118 PM MST THU AUG 30 2007/

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

A MOIST AND UNSTABLE AIR MASS WILL COMBINE WITH WEAK UPPER LEVEL
DISTURBANCES TO PRODUCE ISOLATED TO SCATTERED THUNDERSTORMS ACROSS
THE REGION THROUGH THIS EVENING. BRIEF HEAVY RAIN IS POSSIBLE WITH
THESE STORMS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

UPPER LEVEL HIGH PRESSURE WILL BECOME CENTERED OVER SOUTHERN
NEVADA...BRINGING TEMPERATURES FIVE TO TEN DEGREES ABOVE NORMAL.
HIGH TEMPERATURES WILL BE VERY CLOSE TO EXCESSIVE HEAT WARNING
CRITERIA OVER THE HOLIDAY WEEKEND...AND HUMID CONDITIONS WILL
CONTINUE. THOSE PLANNING OUTDOOR ACTIVITIES DURING THE HOLIDAY
WEEKEND SHOULD TAKE PRECAUTIONS AGAINST THE HEAT AND HUMIDITY. THE
HIGH PRESSURE WILL ALSO SLOWLY MAKE THE AIR MASS LESS UNSTABLE.
ISOLATED THUNDERSTORMS ARE STILL POSSIBLE OVER THE HIGHER TERRAIN
THROUGH SUNDAY...BUT SHOULD BE LIMITED TO MOHAVE COUNTY BEGINNING
ON LABOR DAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME. HOWEVER
SPOTTERS ARE ENCOURAGED TO REPORT ANY HAZARDOUS WEATHER THAT MAY
BE ENCOUNTERED TODAY AND THIS EVENING.

MORGAN