Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000 FXUS65 KVEF 021656 AFDVEF AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LAS VEGAS NV 956 AM PDT THU JUL 2 2015 .SYNOPSIS...A DISTURBANCE LIFTING NORTHEAST ACROSS SOUTHERN CALIFORNIA WILL TRIGGER SHOWERS AND THUNDERSTORMS AT ANYTIME ACROSS MUCH OF THE AREA TODAY. MOIST AND UNSTABLE AIR WILL CONTINUE TO ALLOW FOR SHOWERS AND THUNDERSTORMS AROUND PRIMARILY IN THE AFTERNOON AND EVENING HOURS THROUGH THE HOLIDAY WEEKEND. RELATIVE HUMIDITY VALUES WILL RECOVER EACH NIGHT. TEMPERATURES WILL REMAIN ABOVE NORMAL THROUGH THE WEEKEND WITH A SLIGHT DROP EARLY NEXT WEEK. THERE MAY ALSO BE A GRADUAL DECREASE IN THE COVERAGE OF SHOWERS AND THUNDERSTORMS BY THEN. && .UPDATE...ACTIVITY ASSOCIATED WITH A WAVE WHICH WAS MOVING NORTHWEST ACROSS THE CWA DECREASED EARLY THIS MORNING. IT LOOKS LIKE SOMEWHAT DRIER AND MORE STABLE AIR MOVING IN BEHIND THE WAVE SO CONVECTION IS NOT EXPECTED TODAY ACROSS THE FAR SOUTHERN PART OF THE FORECAST AREA. ELSEWHERE IT WILL STILL BE FAIRLY MOIST AND UNSTABLE WITH THE BEST CHANCE OF THUNDERSTORMS ACROSS THE NORTH AND OVER THE SPRING MOUNTAINS ACCORDING TO MUCH OF THE 12Z MODEL DATA THAT HAS COME IN. THIS IS IN LINE WITH THE INHERITED FORECAST AND NO UPDATES ARE ANTICIPATED THIS MORNING. -HARRISON- && .AVIATION...FOR MCCARRAN...SHRA/TSRA WILL END AFTER 15Z THIS MORNING. THINGS SHOULD STAY DRY THIS AFTERNOON AND EVENING WITH POSSIBLY AN ISOLATED SHRA/TSRA IN THE HIGHER MOUNTAINS AROUND THE VALLEY. LOOK FOR IMPROVING CIGS AND VSBY THIS AFTERNOON WITH MAINLY SCT CLOUDS AOA 15K FEET. WINDS WILL GENERALLY FAVOR DIURNAL DIRECTIONAL TRENDS WITH GUSTS TO AROUND 20 KTS EXPECTED IN THE LATE AFTERNOON AND EARLY EVENING. FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST CALIFORNIA...MAINLY SCT-BKN CLOUDS AOA 15K FEET WITH BASES AS LOW AS 6K-10K FEET IN AND NEAR ANY SHRA/TSRA. OUTSIDE OF THUNDERSTORM ACTIVITY...WINDS SHOULD FAVOR TYPICAL DIURNAL TRENDS. && .PREV DISCUSSION... 306 AM PDT THU JUL 2 2015 .SHORT TERM...TODAY THROUGH SUNDAY NIGHT. THIS CONTINUES TO REMAIN A TOUGH MONSOON PATTERN TO NAIL DOWN MORE THAN A FEW HOURS OUT. THAT SAID, WE ARE LIKELY GOING TO START THINGS OFF ON THE INTERESTING SIDE TODAY BASED ON HOW THE RADAR HAS FILLED BACK IN OVER THE LAST HOUR. A BROAD DISTURBANCE IN THE MID-LEVELS OF THE ATMOSPHERE CONTINUES TO WORK NORTHWEST ACROSS SOCAL INTO CENTRAL CALIFORNIA THIS MORNING WHICH COMBINED WITH A SOUTHEAST TO WEST ORIENTED JET STREAM RUNNING AROUND 60 KTS+ AT 250 MB OFF THE CALIFORNIA COAST WAS HELPING TO SERVE AS A LIFTING MECHANISM ON A LARGER SCALE FOR CONVECTION THIS MORNING. WE REALLY NEVER SAW EVERYTHING SHUT DOWN YESTERDAY EVENING AND THUS THE ACTIVITY PRESENTLY OVER SOUTHERN NEVADA WAS FED OFF WHAT WAS GENERATED ACROSS NORTHWEST ARIZONA LATER YESTERDAY EVENING. THE HRRR DID A GOOD JOB LAST EVENING LATCHING ONTO THIS AND THUS NOW THAT WE ARE SEEING IT BECOME REALITY, I WENT AHEAD AND SIGNIFICANTLY INCREASED POPS FOR THE REST OF THIS MORNING ACROSS MUCH OF CLARK COUNTY, INCLUDING THE LAS VEGAS VALLEY. THE MAIN HAZARDS WILL BE LIGHTNING (WHICH HAS BEEN QUITE IMPRESSIVE TO VIEW OUT THE WINDOW WITH THE SIZE OF THE CG STRIKES), DOWNPOURS POTENTIALLY CAUSING MINOR FLOODING AND WIND GUSTS. ONCE WE MOVE THROUGH THE MORNING, THIS ACTIVITY SHOULD WORK WEST TOWARD SOUTHERN NYE AND SOUTHERN INYO COUNTIES. AS A RESULT, THE NORTHWEST PART OF THE CWFA SHOULD STAY RATHER CLOUDY TODAY AND HIGHS WERE LOWERED OVER THAT AREA A FEW DEGREES. ACROSS LAS VEGAS, ONCE WE SEE SHOWERS AND THUNDERSTORMS END BY LATER THIS MORNING OR AT THE LATEST EARLY THIS AFTERNOON WE WILL PROBABLY BE WORKED OVER ENOUGH THAT THINGS SHOULD QUIET DOWN THIS AFTERNOON. HOWEVER, WE MAY BE A BIT TOO MOIST AND CLEAR SLOWLY ENOUGH THAT WE STILL MAY BE TOO WARM ON THE HIGH TEMP FOR TODAY. THE FLOW ALOFT TODAY REMAINS SOUTHEAST AND AS A RESULT, POPS WERE KEPT DOWN ACROSS MOHAVE COUNTY, WHICH MAY SEE SOME ACTIVITY THIS MORNING AND THIS AFTERNOON MAINLY IN THE PLATEAU REGION. FURTHER SOUTHWEST IN MOHAVE COUNTY AND EXTENDING INTO SOUTHERN SAN BERNARDINO COUNTY IT LOOKS TOO STABLE TODAY TO SEE MUCH AND POPS WERE TRIMMED BACK. WITH THE FLOW STAYING SOUTHEAST ALOFT, THERE IS LESS OF A RISK THIS EVENING FOR MUCH ACTIVITY TO WORK INTO THE LAS VEGAS VALLEY OR COLORADO RIVER VALLEY BELOW HOOVER DAM. THE MOST ACTIVE AREAS THIS EVENING LOOK TO BE TO THE NORTH AND NORTHWEST OF LAS VEGAS. OVERALL WE REMAIN WITH A ROAD RIDGE ALOFT ACROSS THE AREA THAT SITS AROUND THROUGH THE HOLIDAY WEEKEND. WE LOOK TO SEE AN AREA OF NVA ENTER MUCH OF THE CWFA ON FRIDAY WHICH WOULD FAVOR A LACK OF CONVECTIVE ACTIVITY. FOR NOW, POPS WERE LEFT ALONE BUT MAY NEED TO BE LOWERED. THE BEST ODDS LOOK TO BE OVER THE SOUTHERN GREAT BASIN WHERE INSTABILITY AND CAPE IS STILL NOTED AND ACTIVITY POPS UP OVER THE TERRAIN DRIVEN BY HEATING. AN AREA OF LOW PRESSURE IN THE MID/UPPER LEVELS OFF THE BAJA IS SLATED TO MOVE NORTH TO OFF SOCAL ON FRIDAY AND THEN OFF THE COAST OF CENTRAL CALIFORNIA ON SATURDAY. THIS FEATURE SHOULD LIKELY HELP SHOWERS AND THUNDERSTORMS DEVELOP OVER THE SOUTHERN SIERRA AND THUS WE SHOW AN INCREASE IN POPS HERE. ELSEWHERE IT LOOKS STABLE ENOUGH THAT VERY LITTLE ACTIVITY MAY GET GOING WITH WHATEVER THAT CAN BE DRIVEN BY HEATING AND OVER THE HIGHEST TERRAIN. THUS FOR MOST FOLKS ON THE 4TH IT SHOULD BE DRY BUT STILL ABOVE AVERAGE FOR TEMPS WITH SLIGHTLY HIGHER THAN AVERAGE HUMIDITY (SURFACE DEWPOINTS BETWEEN 40 AND 50 DEGREES). BY SUNDAY THE FLOW ALOFT STARTS TO GO MORE SOUTH TO SOUTHWEST WHICH WILL RESULT IN THINGS STARTING TO DRY OUT MORE, ESPECIALLY IN THE SOUTHWEST AND SOUTH-CENTRAL CWFA. POPS WERE KEPT MAINLY FOR THE SOUTHERN GREAT BASIN, WHICH LOOKS TO HAVE THE BEST SHOT AT A SHOWER OR THUNDERSTORM AS WELL AS THE SPRING MOUNTAINS AND EASTERN MOHAVE COUNTY. I DID LOWER LOW TEMPS A TOUGH SATURDAY AND SUNDAY NIGHTS AS WE DRY OUT AND SEE HEIGHTS LOWER A LITTLE AS WELL. .LONG TERM...MONDAY THROUGH THURSDAY. IT APPEARS THE FIRST BREAK IN THE MONSOONAL PATTERN WILL OCCUR EARLY NEXT WEEK AS AN INCREASINGLY DRY SOUTHWEST FLOW SPREADS INLAND ACROSS SOUTHEAST CALIFORNIA...SOUTHERN NEVADA AND NORTHWEST ARIZONA. THIS DRY AND STABLE FLOW IS ASSOCIATED WITH A PACIFIC TROUGH THAT APPROACHES THE WEST COAST THEN PARKS OFFSHORE MUCH OF NEXT WEEK. THIS PATTERN SHOULD SCOUR OUT ANY LINGERING MOISTURE ACROSS OUR FORECAST AREA BY WEDNESDAY AND MAYBE AS EARLY AS TUESDAY. I WILL KEEP THE MENTION OF A SLIGHT CHANCE OF THUNDERSTORMS MONDAY AND TUESDAY MAINLY OVER THE SOUTHERN SIERRA...CENTRAL NEVADA AND NORTHWEST ARIZONA ZONES MONDAY AND TUESDAY. TEMPERATURES WILL BE RUNNING CLOSE TO NORMAL...BUT THAT IS STILL QUITE HOT WITH HIGHS GENERALLY 105-110 DEGREES ACROSS THE MOJAVE DESERT AND COLORADO RIVER REGION. && .SPOTTER INFORMATION STATEMENT...SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. && $$ UPDATE...ADAIR SHORT TERM/AVIATION...STACHELSKI LONG TERM...ADAIR

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