AREA FORECAST DISCUSSION

 
 FXUS65 KVEF 120629 CCA
 AFDVEF
 
 AREA FORECAST DISCUSSION...CORRECTED
 NATIONAL WEATHER SERVICE LAS VEGAS NV
 930 PM PDT SUN MAY 11 2008
 
 .SYNOPSIS...A LOW PRESSURE SYSTEM OVER THE PACIFIC NORTHWEST
 WILL MOVE INTO THE NORTHERN GREAT BASIN TONIGHT. THE STORM SYSTEM 
 WILL THEN STRENGTHEN AND DIVE SOUTHEAST INTO UTAH MONDAY AND INTO 
 ARIZONA BY TUESDAY. THIS WILL RESULT IN A CHANCE OF THUNDERSTORMS 
 FOR PORTIONS OF SOUTHERN NEVADA AND NORTHWEST ARIZONA ALONG WITH 
 WINDY CONDITIONS ACROSS SAN BERNARDINO COUNTY. TEMPERATURES WILL 
 FALL TO BELOW NORMAL LEVELS ON TUESDAY BEHIND A COLD FRONT. DURING 
 THE LATTER HALF OF THE WORK WEEK TEMPERATURES WILL WARM BACK TO 
 ABOVE NORMAL. 
 &&
 
 .UPDATE...THE 00Z NAM AND GFS CAME IN WITH QUITE SIMILAR SOLUTIONS 
 OF THE FORECAST TRACK OF THE PACIFIC NORTHWEST LOW OVER THE NEXT 
 36-48 HOURS. THEY BOTH BASICALLY SUPPORT THE TRENDS IN THE GOING 
 FORECAST. HOWEVER...A FEW WIND ISSUES NEED TO BE ADDRESSED. RECENT 
 OBSERVATIONS THROUGH 0230 UTC INDICATED A PROBABLE DOWNSLOPE EVENT 
 DEVELOPING IN THE EASTERN SIERRA NEAR INDEPENDENCE WITH A GUST TO
 65 MPH RECORDED ABOVE 5000 FEET. THOUGH 12Z LOCAL 4KM MODEL 
 CROSS-SECTIONS DO NOT GIVE A STRONG SIGNATURE OF THESE 
 CONDITIONS...WHAT SIGNATURE THEY DO GIVE SHOWS AN INCREASING TREND 
 THROUGH AT LEAST 12Z...AND POSSIBLY A FEW HOURS LONGER. WILL BE 
 ISSUING A HIGH WIND WARNING FOR THE EASTERN SIERRA ABOVE 5000 FEET 
 AND A WIND ADVISORY FOR THE OWENS VALLEY THROUGH 9 AM MONDAY. 
 ALSO...WILL ISSUE A WIND ADVISORY FOR WESTERN SAN BERNARDINO COUNTY 
 FROM NOON UNTIL 10 PM MONDAY. REST OF FORECAST TRENDS AS DETAILED 
 BELOW LOOK GOOD.
 &&
 
 .PREV DISCUSSION.../315 PM PST SUN MAY 11 2008/
 
 .SHORT TERM...TEMPERATURES DID JUMP UP NICELY AFTER SOUTHWEST 
 BREEZES KICKED IN DURING THE EARLY AFTERNOON. WE SHOULD LOSE THE 
 GUSTS THIS EVENING...HOWEVER BOUNDARY LAYER SHOULD STAY MIXED 
 OVERNIGHT AS TROUGH FROM THE THE PACIFIC NORTHWEST MOVES INTO THE 
 NORTHERN GREAT BASIN. DISAPPOINTED IN MODEL CONSISTENCY...ESPECIALLY 
 FROM THE GFS. THE GFS HAS TRENDED TOWARD THE NAM WHICH HAS BEEN 
 DIGGING THE LOW FURTHER OFF TO OUR EAST ACROSS UTAH MONDAY INTO THE 
 FOUR CORNERS AREA TUESDAY. THE ECMWF HAS REMAINED CONSISTENT BEING 
 MORE AGGRESSIVE DIGGING THE LOW FURTHER WEST ACROSS SOUTHERN NEVADA 
 MONDAY EVENING AND INTO SOUTHWEST ARIZONA TUESDAY. THE ECMWF 
 SOLUTION DOES HAVE SUPPORT FROM THE CANADIAN. AT ANY RATE NOT TO 
 BORE YOU WITH MODEL DETAILS...BEST DYNAMICS ALONG THE COLD FRONT AND 
 INSTABILITY WILL BE OVER LINCOLN COUNTY MONDAY AFTERNOON. AREA WORKS 
 SOUTH ACROSS SOUTHERN NEVADA AND NORTHWEST ARIZONA MONDAY EVENING 
 BEFORE ENDING IN MOHAVE COUNTY TUESDAY MORNING. STILL LOOKS LIKE 
 WIND ADVISORY CRITERIA WILL BE MET IN THE WESTERN MOJAVE DESERT OF 
 SAN BERNARDINO COUNTY LATE MONDAY MORNING THROUGH THE EVENING HOURS. 
 USUALLY WOULD FEEL CONFIDENT ISSUING THE ADVISORY THIS AFTERNOON BUT 
 DUE TO DIFFERING SOLUTIONS WILL LET FOLLOWING SHIFTS HAVE A LOOK AT 
 THE 00Z OUTPUT BEFORE MAKING FINAL DETERMINATION. ON TUESDAY...WITH 
 OUR AREA ON THE BACKSIDE OF LOW IT WILL BE COOLER WITH WINDY 
 CONDITIONS DOWN THE COLORADO RIVER. TEMPERATURES WILL START TO 
 REBOUND AND WINDS DECREASE WEDNESDAY AS LOW MOVES EAST ACROSS 
 SOUTHERN NEW MEXICO. 
 
 .LONG TERM...THURSDAY THROUGH SUNDAY. THE OPERATIONAL MODELS ALL 
 AGREE THAT A HIGH SITTING OFF THE CALIFORNIA COAST WILL SPREAD 
 EASTWARD DURING THIS TIME PERIOD.  THE QUESTION CONTINUES TO 
 BE...EXACTLY HOW STRONG WILL THE HIGH BE...AND WHERE WILL IT SET 
 UP.  THE ANSWERS TO THESE QUESTIONS WILL HAVE A BIG IMPACT ON 
 TEMPERATURES.  THE GUIDANCE NUMBERS CONTINUE TO BE ALL OVER THE 
 PLACE FROM RUN TO RUN DUE TO THE UNCERTAINTY.  THE 12Z MEX FOR LAS 
 VEGAS ON SATURDAY HAS A HIGH OF 101 WHERE THE 00Z MEX HAD 91.  AT 
 THIS TIME WILL DEVIATE LITTLE FROM THE INHERITED FORECAST AND STAY 
 CLOSE TO ENSEMBLE AVERAGE OR HIGH MEMBER.
 
 TOWARD THE END OF THE EXTENDED THE ENSEMBLES DEVELOP A CLOSED LOW 
 OFF THE SOUTHERN BAJA COAST BY FRIDAY.  THE OPERATIONAL GFS AND 
 EUROPEAN ARE SLOWER TO AGREE.
 &&
 
 .AVIATION...FOR MCCARRAN...THE WIND WILL STAY OUT OF THE SOUTHWEST 
 OVERNIGHT THEN SHIFT MORE FROM THE WEST MONDAY IN PREPARATION FOR A 
 COLD FRONT THAT MOVES ACROSS THE AREA MONDAY EVENING. THERE IS 
 LIMITED MOISTURE WITH THIS SYSTEM BUT LIFT ALONG THE COLD FRONT 
 COULD BE SUFFICIENT TO GENERATE AN ISOLATED SHOWER OR THUNDERSTORM 
 OVER THE SURROUNDING MOUNTAINS OR IN THE MORMON MESA CORRIDOR LATE 
 MONDAY AFTERNOON.
 
 FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST 
 CALIFORNIA...GUSTY SOUTHERLY WINDS WILL BE EXPECTED FOR THE FORECAST 
 PERIOD. WINDS WILL SHIFT TO A MORE WEST AND NORTHWEST DIRECTION 
 MONDAY AS A COLD FRONT MOVES THROUGH THE AREA. PORTIONS OF MOHAVE 
 COUNTY ARIZONA AND SAN BERNARDINO COUNTY CALIFORNIA WILL EXPERIENCE 
 THE STRONGEST WINDS ASSOCIATED WITH THE FRONT AFTER 18Z. SKIES WILL 
 BE MOSTLY CLEAR TONIGHT WITH AN INCREASE IN CLOUD COVER ALONG A COLD 
 FRONT MONDAY...ESPECIALLY ACROSS SOUTHERN NEVADA AND NORTHWEST 
 ARIZONA.
 &&
 
 .FIRE WEATHER...WINDS WILL INCREASE IN SOME AREAS MONDAY AS A  
 TROUGH INTENSIFIES AND MOVES INTO UTAH. WIND GUSTS AROUND 35 MPH ARE 
 A GOOD POSSIBILITY IN SAN BERNARDINO COUNTY AND MUCH OF MOHAVE 
 COUNTY. VERY HIGH TO EXTREME FIRE DANGER IS ANTICIPATED OVER MOHAVE 
 COUNTY ALONG WITH RELATIVE HUMIDITY BELOW 15 PERCENT. A FIRE WEATHER 
 WATCH IS IN EFFECT FOR LATE MONDAY MORNING THROUGH MONDAY EVENING 
 FOR ARIZONA FIRE ZONE 102. FUEL STATUS IS DEPICTED AS DRY IN SAN 
 BERNARDINO COUNTY RATHER THAN THE VERY DRY THAT IS REQUIRED FOR RED 
 FLAG CRITERIA SO DID NOT INCLUDE FIRE ZONE 228 IN THE WATCH. 
 &&
 
 .VEF WATCHES/WARNINGS/ADVISORIES...
 NV...NONE.
 AZ...FIRE WEATHER WATCH FROM MONDAY MORNING THROUGH MONDAY EVENING 
      FOR AZZ102.
 CA...HIGH WIND WARNING UNTIL 9 AM PDT MONDAY FOR ZONE 519. WIND
      ADVISORY UNTIL 9 AM PDT MONDAY FOR ZONE 520. WIND ADVISORY
      FROM NOON UNTIL 10 PM PDT MONDAY FOR ZONE 523.
 &&
 
 

 
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