000
FXUS65 KVEF 061144
AFDVEF
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
344 AM PST TUE JAN 6 2009
.SYNOPSIS...HIGH PRESSURE OVER THE EASTERN PACIFIC WILL SHIFT INLAND
RESULTING IN OCCASIONAL HIGH CLOUDS AND A WARMING TREND THROUGH
THURSDAY. A LOW PRESSURE SYSTEM IS EXPECTED TO BRING A CHANCE OF
LIGHT PRECIPITATION AND COOLER TEMPERATURES TO THE AREA ON FRIDAY.
NORTH WINDS WILL DEVELOP BEHIND A COLD FRONT FRIDAY NIGHT LEADING TO
BREEZY TO WINDY CONDITIONS THIS WEEKEND.
&&
.SHORT TERM...GREAT BASIN AND THE MOJAVE DESERT REMAIN UNDER A
NORTHWEST FLOW AS SATELLITE SHOWS MASSIVE RIDGE OVER THE EASTERN
PACIFIC. NORTHWEST FLOW WILL NOT BE AS DIRTY AS MONDAY. AREA WILL
MAINLY BE BLANKETED BY HIGH CLOUDS WITH SOME LOWER CLOUDS MIXED IN
GENERALLY ACROSS THE NORTH. CHALLENGE OF THE DAY WILL BE
TEMPERATURES. VALLEY INVERSIONS AND EXTENSIVE CLOUD COVER YESTERDAY
REALLY SUPPRESSED HIGH TEMPERATURES. LESS CLOUD COVER TODAY WILL
HELP...HOWEVER VALLEY INVERSIONS WILL REMAIN INTACT DUE TO LIGHT
SURFACE WINDS. SIMILAR TO PREVIOUS SHIFT UNDERCUT MOS GUIDANCE FOR
LAS VEGAS. HEAD TO THE MOUNTAIN FOR WARMER TEMPERATURES AS MODELS
INDICATE FURTHER WARMING OF 850/700 TEMPERATURES ABOVE THE INVERSION
TODAY. RIDGE OVER THE EASTERN PACIFIC MOVES INLAND OVER THE GREAT
BASIN WEDNESDAY AND THURSDAY FOR DRY AND MILD TEMPERATURES IN THE
HIGHER ELEVATIONS. THE `BROWN CLOUD` WILL ENHANCE IN THE LAS VEGAS
VALLEY THROUGH THURSDAY AS THE INVERSION WILL BE DIFFICULT TO BREAK
EACH DAY DUE TO LACK OF WINDS. THEREFORE HAVE CONTINUED TO UNDERCUT
GUIDANCE BY A FEW DEGREES AS WELL. NEAR THE END OF THE SHORT TERM
PERIOD THURSDAY NIGHT NEXT TROUGH WILL START SPREADING LIGHT
PRECIPITATION OVER THE SOUTHERN SIERRA NEVADA/OWENS VALLEY AND
CENTRAL NEVADA.
.LONG TERM...AN UPPER LOW OVER THE GREAT BASIN FRIDAY ESSENTIALLY
BREAKS INTO TWO PARTS WITH THE NORTHERN ENERGY MOVING ALONG THE
NORTHERN ROCKIES/PLAINS WHILE THE SOUTHERN ENERGY HEADS SOUTHEAST
THROUGH NEVADA...UTAH AND ARIZONA. THE 00Z/06Z GFS CONTINUES TO
FORECAST A STRONGER SYSTEM MOVING THROUGH NEVADA AND CLOSING OFF
OVER WESTERN ARIZONA. THE 00Z ECMWF/GEM AND THE MAJORITY OF GEFS
MEMBERS HOLD TIGHT WITH A POSITIVELY TILTED OPEN WAVE TROUGH SLIDING
THROUGH THE AREA. HOWEVER...A COUPLE OF GEFS MEMBERS NOW SUPPORT THE
OPERATIONAL GFS SOLUTION SO ALTHOUGH THIS FORECAST PACKAGE MAINLY
FOLLOWS PREVIOUS THINKING...IT NOW INCORPORATES SOME OF THE GFS
DETAILS. THIS INCLUDES EXPANDING A SLIGHT CHANCE OF SHOWERS TO
INCLUDE MOST OF THE NORTHERN MOUNTAIN REGION AND NOW INCLUDES THE
CLARK COUNTY MOUNTAINS. AVAILABLE MOISTURE IS STILL LIMITED SO
RAIN/SNOW AMOUNTS ARE EXPECTED TO BE LIGHT. SOME LINGERING SHOWER
EFFECTS ARE POSSIBLE FRIDAY NIGHT INTO EARLY SATURDAY BUT THE MAIN
CONCERN SHIFTS TO WIND. FAIRLY STRONG SURFACE HIGH PRESSURE BUILDS
NORTH OF THE AREA LATE FRIDAY AND CONTINUES TO BE PRESENT THROUGH AT
LEAST EARLY NEXT WEEK. THIS WILL KEEP A PRONOUNCED NORTHERLY SURFACE
FLOW ACROSS THE CWA WITH BREEZY TO WINDY CONDITIONS EXPECTED OVER
THE WEEKEND. THE NORTH WINDS AND DAYTIME SURFACE INVERSIONS SHOULD
HOLD TEMPERATURES DOWN NEAR OR SLIGHTLY BELOW NORMAL IN VALLEY
LOCATIONS THROUGH MONDAY. THUS...HIGH TEMPERATURES WERE ADJUSTED
DOWN A COUPLE OF DEGREES SUNDAY AND MONDAY.
&&
.AVIATION...FOR MCCARRAN...LIGHT AND VARIABLE WINDS ARE EXPECTED
THROUGH EARLY THURSDAY WITH VARIABLE HIGH CLOUDS AOA 25KFT.
FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...GENERALLY LIGHT AND VARIABLE WINDS THROUGH EARLY
THURSDAY WITH VARIABLE HIGH CLOUDS AOA 25K FT.
&&
.VEF WATCHES/WARNINGS/ADVISORIES...
NV...NONE.
AZ...NONE.
CA...NONE.
&&
$$
PIERCE/SALMEN
HTTP://WEATHER.GOV/LASVEGAS
