101 FXUS65 KPSR 122121 AFDPSR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ 220 PM MST TUE APR 12 2016 .SYNOPSIS... MUCH WARMER AND DRIER WEATHER WILL RETURN TO THE REGION WEDNESDAY AND THURSDAY AS HIGH PRESSURE SETTLES OVER THE AREA. ANOTHER PACIFIC WEATHER SYSTEM WILL MOVE THROUGH THE WESTERN UNITED STATES FRIDAY AND SATURDAY BRINGING WINDY CONDITIONS AND MUCH COOLER WEATHER BACK TO THE REGION. && .DISCUSSION... A NICELY DEFINED COLD CORE SHORTWAVE HAS NOW EJECTED INTO SOUTH CENTRAL NEW MEXICO WITH HIGHER HEIGHTS AND SUBSIDENCE FEEDING INTO THE LEFT REAR JET CORE BUILDING INTO SERN CALIFORNIA/SWRN ARIZONA. THE COMBINATION OF WEAK DEFORMATION...MODESTLY STEEP MIDLEVEL LAPSE RATES...AND MINOR INSTABILITY (MUCAPE NEARING 500 J/KG) HAVE SUPPORTED NUMEROUS SHOWERS AND EMBEDDED THUNDERSTORMS ALONG THE MOGOLLON RIM AND WHITE MOUNTAINS. WHILE STEERING FLOW AND INSTABILITY PARAMETERS MAY SUPPORT SHOWERS/STORMS PROPAGATING INTO PARTS OF SRN GILA COUNTY...VERTICAL AND HORIZONTAL MIXING OF DRY AIR AT LOWER ELEVATIONS ARE CREATING AN ENVIRONMENT MORE HOSTILE TOWARDS MAINTAINING CONVECTION DIRECTED SOUTH DOWN THE I-17 CORRIDOR. A BLEND OF RECENT HRRR ITERATIONS AND HIGH RESOLUTION CONVECTIVE MODELS MOST ACCURATELY DEPICTS THIS EVOLUTION KEEPING CONVECTIVE ELEMENTS PRIMARILY OVER HIGHER TERRAIN FEATURES INTO EARLY EVENING BEFORE DISSIPATING ACTIVITY WITH LOSS OF DAYTIME HEATING. DAMPENED WEAK RIDGING/QUASI-ZONAL FLOW WILL BECOME ESTABLISHED OVER SWRN CONUS WEDNESDAY AND THURSDAY WITH H5 HEIGHTS STAY IN A 573- 579DM RANGE. FULL INSOLATION WILL CREATE DEEP BOUNDARY LAYER MIXING WHILE MODEL H8 TEMPERATURES INCREASE TOWARDS 16-19C RANGE BY THURSDAY AFTERNOON. MODEL SPREAD HAS DECREASED SOMEWHAT WITH RECENT MODEL OUTPUT YIELDING BETTER CONFIDENCE IN BEST PERFORMING GUIDANCE PEAKING AFTERNOON TEMPERATURES IN THE MIDDLE 80S TO LOWER 90S. FRIDAY AND SATURDAY... A COLDER PACIFIC WEATHER SYSTEM WILL DESCEND FROM THE PACIFIC NORTHWEST INTO THE REGION FRIDAY AND FRIDAY NIGHT. DIFFERENCES AMONG ALL OPERATIONAL AND ENSEMBLE MEMBERS ABOUND WITH LITTLE RUN TO RUN CONSISTENCY...MUCH LESS AGREEMENT ON TRACK AND INTENSITY. ONE MEASURE OF CONSISTENCY IS THE CONTINENTAL TRACK OF THE LOW DROPPING SOUTH OVER GREAT BASIN/ROCKIES...WHICH CONTINUES TO FAVOR SHOWER CHANCES DURING THE DAYLIGHT HOURS OVER HIGHER TERRAIN WITH MUCH OF THE LOWER ELEVATION COMMUNITIES CLEARING. THE LARGEST IMPACT FROM THIS WEATHER SYSTEM WILL ALMOST CERTAINLY BE STRONGER WINDS THROUGH SE CALIFORNIA/WRN ARIZONA. OPERATIONAL GFS WIND ANOMALIES ARE TOWARDS THE STRONGER END OF THE MODEL SPREAD ENVELOPE (NEAR 40KT AT H8)...HOWEVER EVEN THE NAEFS AVERAGE V-WIND H8-H7 ANOMALIES LIE TOWARDS THE SEASONALLY EXTREME THRESHOLD. THUS...THERE IS SUFFICIENT SIGNAL TO START MENTIONING BLOWING DUST POTENTIAL FRIDAY AFTERNOON IN ADDITION TO ELEVATED FIRE DANGER. WHILE TAKING A BLENDED APPROACH TO THE EXTENDED FORECAST...COOLER TEMPERATURES ALSO LOOK TO BE EXTREMELY LIKELY...BUT MOISTURE CONTINUES TO LOOK VERY LIMITED WITH EACH MODEL RUN SO HAVE TRIMMED PRECIPITATION CHANCES BACK TOWARDS MAINLY HIGHER TERRAIN AREAS NORTH AND EAST OF THE PHOENIX METRO. SUNDAY INTO EARLY NEXT WEEK... SUBSTANTIAL ENSEMBLE SPREAD EXISTS DURING THIS PERIOD WITH SOME MEMBERS MORE RAPIDLY EJECTING NEGATIVE HEIGHT ANOMALIES INTO THE PLAINS...WHILE OTHERS LINGER A CLOSED LOW NEAR THE LOCAL REGION THROUGH EARLY NEXT WEEK. THUS...FORECAST CONFIDENCE DECREASES SOMEWHAT DURING THIS TIME FRAME ALBEIT WITH NUMERICAL GUIDANCE NOT DISPLAYING THE AMOUNT OF SPREAD THAT OTHERWISE WOULD BE ANTICIPATED. && .AVIATION... SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL... DRIER AIR FILTERING IN FROM THE WEST TO PRETTY MUCH CLEAR ALL REMAINING CLOUDS BY LATE THIS EVENING...WITH CLEAR SKIES PREVAILING THROUGH THE REST OF THE TAF PERIOD. WINDS TO REMAIN ON THE LIGHT SIDE...MAINLY 10 KTS OR LESS. WIND DIRECTIONS TO MAINLY FOLLOW TYPICAL DIURNAL TRENDS...BUT WITH TYPICAL WESTERLY WINDS PERSISTING LATER INTO THE EVENING THEN USUAL. SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH... MOSTLY CLEAR SKIES AND LIGHT DIURNALLY-DRIVEN WINDS TO PREVAIL THROUGH THE TAF PERIOD. && .FIRE WEATHER... THURSDAY THROUGH MONDAY... ABOVE NORMAL TEMPERATURES WILL PERSIST THURSDAY ALONG WITH A SLIGHT DRYING TREND. THEREAFTER...A STRONG LOW PRESSURE SYSTEM WILL DROP DOWN OUT OF THE NORTHERN ROCKIES TOWARDS THE FOUR CORNERS. BIGGEST IMPACT FROM THIS SYSTEM WILL BE AN INCREASE IN WIND. VERY BREEZY TO WINDY CONDITIONS ARE EXPECTED EACH AFTERNOON BEGINNING THURSDAY AND CONTINUING THROUGH SATURDAY. ELEVATED FIRE DANGER WILL BE POSSIBLE FOR A FEW HOURS EACH AFTERNOON THROUGH SATURDAY...PARTICULARLY ACROSS THE HIGHER TERRAIN OF SOUTHWESTERN ARIZONA AND SOUTHEASTERN CALIFORNIA. ALTHOUGH THE DRY AIR WILL PERSIST SUNDAY AND INTO NEXT MONDAY...THE THREAT FOR HAZARDOUS FIRE WEATHER CONDITIONS WILL DECREASE AS THE LOW PRESSURE SYSTEM MOVES EASTWARD AND WINDS SUBSIDE. && .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX PREVIOUS DISCUSSION...MO/MEYERS AVIATION...PERCHA FIRE WEATHER...HIRSCH