776
FXUS65 KVEF 071658
AFDVEF
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
955 AM PDT TUE OCT 7 2008
SYNOPSIS
DRY AND MILD CONDITIONS THE FIRST HALF OF THE WEEK WILL
GIVE WAY TO COOL...UNSETTLED AND WINDY WEATHER AS A STRONG LOW
PRESSURE SYSTEM DIVES OUT OF WESTERN CANADA AND INTO THE GREAT BASIN
THIS WEEKEND.
UPDATE
THE 12Z NAM AND GFS ARE NOW IN GOOD AGREEMENT WITH THE
ECMWF THROUGH FRIDAY AFTERNOON WITH THE EXPECTED COLD UPPER LOW
DROPPING DOWN FROM THE NORTH. THIS CONFIRMS THE GOING FORECAST
TRENDS DETAILED BELOW AND NO IMMEDIATE CHANGES ARE NEEDED. -ADAIR-
PREV DISCUSSION
/312 AM PDT TUE OCT 7 2008/
SHORT TERM
SATELLITE SHOWS CLEAR SKIES AREAWIDE UNDER FLAT RIDGE
OF HIGH PRESSURE. THIS FLAT RIDGE WILL REMAIN IN PLACE THROUGH
WEDNESDAY WITH DRY AND WARM WEATHER CONTINUING. BY WEDNESDAY NIGHT
AND THURSDAY...A SHARPENING TROUGH DIGGING OUT OF BRITISH COLUMBIA
WILL BRING FALLING HEIGHTS...INCREASING WINDS...AND SLIGHTLY LOWER
TEMPERATURES. THE ASSOCIATED COLD FRONT IS EXPECTED TO CROSS THE
SOUTHERN GREAT BASIN THURSDAY...AND REACH THE MOJAVE DESERT BY THE
END OF THE SHORT TERM FRIDAY MORNING. THE MAIN EFFECTS IN THE SHORT
TERM WILL BE INCREASING SOUTHWEST WINDS AHEAD OF THE FRONT WHICH
WILL THEN SHIFT TO NORTHERLY BEHIND IT. RAW MODEL OUTPUT AND
STATISTICAL GUIDANCE ALL SUGGEST PREFRONTAL WINDS REMAINING BELOW
ADVISORY CRITERIA.
LONG TERM...FRIDAY MORNING THROUGH MONDAY
MODELS HAVE REALLY COME
VERY CLOSE TO EACH OTHER WITH THE ECMWF BEING THE ONE MOST
CONSISTENT IN ITS SOLUTION. BY FRIDAY MORNING...A BIG CLOSED LOW
DEVELOPS OVER NORTHERN NEVADA IN THE BASE OF THE TROUGH. HELD ONTO
THE POPS AND EVEN UPPED THEM A LITTLE AND EXPANDED COVERAGE. DO NOT
EXPECT SIGNIFICANT ACCUMULATIONS OF RAIN OR SNOW WITH THIS SYSTEM AS
IT WILL HAVE A LONG OVER LAND TRAJECTORY AND WILL ONLY HAVE THE
MOISTURE IT BROUGHT WITH IT TO WORK ON.
MAJOR CONCERN WITH THIS SYSTEM WILL BE THE WINDS. 700MB TEMPERATURE
AND SURFACE PRESSURE GRADIENTS INDICATE A POTENTIAL FOR WIND
ADVISORIES OR WARNINGS FRIDAY AND EARLY SATURDAY. THIS LOOKS SIMILAR
TO FRONTAL PASSAGE LAST SPRING THAT BROUGHT STRONG WINDS TO THE LAS
VEGAS VALLEY.
WITH THAT FRONTAL PASSAGE FRIDAY WILL COME MAXIMUM TEMPERATURE DROPS
OF 15 TO 20 PLUS DEGREES FROM THURSDAY TO SATURDAY AFTERNOON. SOME
WARMING WILL OCCUR SUNDAY AS THE UPPER LOW MOVES OFF TO THE
NORTHEAST BUT WILL BE TEMPERED BY COOL NORTH FLOW. MONDAY WILL SEE
BETTER WARMING AS RIDGING BUILDS IN FROM THE EASTERN PACIFIC.
AVIATION...FOR MCCARRAN...NO SIGNIFICANT WEATHER EXPECTED
ANOTHER
DAY OF MOSTLY SUNNY SKIES ACCOMPANIED BY LIGHT AND VARIABLE WINDS.
WEDNESDAY WILL SEE THE SAME CONDITIONS REPEATED. A SIGNIFICANT
CHANGE IN THE WEATHER WILL OCCUR FRIDAY AND INTO EARLY SATURDAY AS A
STRONG COLD FRONT WILL PUSH THROUGH SOUTHERN NEVADA. MAJOR CONCERN
FOR KLAS WILL BE STRONG WINDS AHEAD OF AND BEHIND THE FRONT. A BIG
TEMPERATURE DROP WILL OCCUR AS WELL BY SATURDAY.
FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...NO SIGNIFICANT WEATHER EXPECTED THROUGH THURSDAY
NIGHT...UNTIL ANOTHER LOW PRESSURE SYSTEM MOVES ACROSS THE AREA FROM
NORTH TO SOUTH...RESULTING IN STRONG WINDS...DECREASED
TEMPERATURES...AND A CHANCE FOR PRECIPITATION ACROSS NORTHERN
LINCOLN...NYE...ESMERALDA...AND INYO COUNTIES.
VEF WATCHES/WARNINGS/ADVISORIES
NV...NONE.
AZ...NONE.
CA...NONE.
MORGAN/JACQUES
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