000 FXUS65 KPSR 061835 AAA AFDPSR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ 1135 AM MST MON JUL 6 2009 .UPDATE...UPDATED AVIATION DISCUSSION. && .SYNOPSIS... DRIER AIR WILL REMAIN OVER THE REGION THROUGH THE COMING WEEK WITH ANY PRECIPITATION CHANCES CONFINED TO THE MOUNTAINS OF EASTERN ARIZONA. TEMPERATURES WILL SHOW LITTLE FLUCTUATION THROUGH MID-WEEK BUT BY THE END OF THIS WEEK NEAR-RECORD OR RECORD TEMPERATURES ARE POSSIBLE. && .DISCUSSION... CLEAR SKIES OVER OUR CWA AT THIS HOUR...JUST SOME DEBRIS CLOUDS HOVERING OVER SE PORTIONS OF THE STATE. IR/VIS SATELLITE SHOWS A DECAYING CONVECTIVE COMPLEX OVER THE CENTRAL GULF OF CALIFORNIA WITH SOME UPPER LEVEL CLOUDS MOVING NORTHWARD. SURFACE OBSERVATIONS ARE OF INTEREST...AS A WEAK SURGE OF MOISTURE IS UNDERWAY AT KNYL AND ALONG PORTIONS OF THE LOWER COLORADO RIVER AND EXTREME SE CA. KYUX VAD WIND PROFILE REVEAL S-SE WINDS AROUND 20KTS UP TO 3000FT WITH ABOUT A 20 DEG JUMP IN THE DEW POINTS IN THE LAST TWO HOURS. THIS SHALLOW MOISTURE BOUNDARY CURRENTLY EXTENDS FROM YUMA E-NE TO ROOSEVELT IN SOUTHERN GILA COUNTY...TDS AVERAGING IN THE IN THE 50S SOUTH OF THIS LINE...UPPER 30S TO NEAR 40 NORTH OF THE LINE. DESPITE THIS...STILL NOT MUCH TO OFFER TO THE DISCUSSION THIS MORNING...AS THE UPPER AIR PLOTS/STREAMLINES INDICATE A MUCH DRIER W-SW FLOW ALOFT WITH THE UPPER LEVEL RIDGE AXIS SMOOSHED AND PUSHED TO THE SOUTHEAST. THE SHALLOW MOISTURE INTRUSION OVER THE SOUTHWEST DESERTS WILL MIX OUT WITH AFTERNOON HEATING AND THE FLOW WILL BE DRY. THIS PATTERN IS DEFINITELY CHARACTERISTIC OF A BREAK IN THE MONSOON. HOWEVER...MODELS STILL CONSISTENT WITH SOME MOISTURE THAT SEEPS NORTHWARD INTO SOUTH-CENTRAL AZ AT TIMES...AND IN A DEGREE OR TWO OF COOLING TO DAYTIME HIGHS TODAY THROUGH WEDNESDAY AS SHORT WAVE TROFS MOVE ACROSS THE NORTHERN TIER OF THE CONUS. INHERITED SHORT TERM FORECAST...ESPECIALLY THE TEMPS/POPS/WX...CAPTURE THIS TREND WELL AND NO CHANGES ARE PLANNED AT THIS TIME. A DRY AND WARM FORECAST TODAY WITH HIGHS SIMILAR TO SUNDAY. PREVIOUS DISCUSSION STILL APPLIES. PREVIOUS DISCUSSION... TUESDAY THROUGH THURSDAY MODELS ARE STILL SUGGESTING A SLIGHT RESURGENCE IN BOUNDARY LAYER MOISTURE FOR MAINLY OUR CENTRAL AND EASTERN CWA...POSSIBLY A WEAK TYPE OF SURGE EVENT. GFS IS NOTABLY MORE AGGRESSIVE AS IT BRINGS THE BOUNDARY LAYER MIXING RATIOS UP TO 10 G/KG WHILE THE ECMWF REMAINS NEAR 8. EVEN IF WE GET AS MUCH MOISTURE AS THE GFS SUGGESTS THERE WILL BE A RATHER DEEP/WARM CAPPING LAYER ABOVE THE BOUNDARY LAYER SUGGESTING MINIMAL CONVECTIVE ACTIVITY FOR THOSE DAYS. STEERING FLOW WILL STILL BE DECIDEDLY OUT OF THE WEST WHICH WOULD KEEP ANY MTN STORMS FROM MOVING INTO THE DESERTS. WILL KEEP THE SLIGHT CHANCE POPS IN THE FORECAST. OWING TO THE MOISTURE EXPECTING A RATHER SLIGHT DROP IN TEMPERATURES THROUGH MID-WEEK. BY FRIDAY H5 RIDGE OVER THE SOUTH-CENTRAL CONUS BEGINS TO AMPLIFY AND EXPAND AS THE TROUGH OVER THE PAC NW RETROGRADES AND WEAKENS. GFS AND ECMWF REMAIN EXCEPTIONALLY CONSISTENT WITH THIS FEATURE. GFS ENSEMBLE MEANS HAVE BEEN AS WELL. QUICK LOOK AT THE NORTH AMERICAN ENSEMBLE FORECAST SYSTEM /NAEFS/...WHICH USES ROUGHLY 40 MEMBERS...IS SHOWING THE SAME H5 PATTERN. VERY LITTLE VARIATION IS NOTED AMONGST THE INDIVIDUAL MEMBERS WHICH IS CONFIRMED BY THE LOW VARIABILITY OF THE MEAN /A STD DEV OF LESS THAN 2 DM/. STANDARDIZED ANOMALIES OF THE GFS H5 HEIGHT FIELD SHOW THE RIDGE PEAKING IN THE PLUS-2 RANGE WHICH CONFIRMS THIS WILL BE A SIGNIFICANT EVENT. IN SHORT...CONFIDENCE CONTINUES TO CLIMB THAT WE/RE IN FOR AN EXCEPTIONALLY HOT PERIOD THIS WEEKEND. AS MENTIONED LAST NIGHT...COMPARING THE EXPECTED WEATHER PATTERN FOR THIS WEEKEND TO A COMPOSITE ANALYSIS OF THE TOP 10 HOTTEST DAYS IN PHOENIX /ROUGHLY 115 DEG F AND HIGHER/ REVEALS A STRIKING SIMILARITY BETWEEN THE TWO. MODELS ARE STILL FORECASTING H85 TEMPS TO PEAK NEAR 32-36 DEG C ACROSS OUR CWA ON SATURDAY...WHICH WHEN MIXED TO THE SURFACE YIELDS MAX TEMPS FOR THE DESERTS OF 115-120 DEGREES. LAST... MEX NUMBERS HAVE CONTINUED TO INCREASE THOUGH I CONSIDER THE STATISTICAL GUIDANCE TO BE A LAGGING INDICATOR FOR THIS EVENT. GIVEN ALL THIS...RAISED MAX TEMPERATURES AGAIN FRIDAY THROUGH SUNDAY FROM WHAT WAS CURRENTLY IN THE GRIDS. ALSO RAISED MIN TEMPERATURES DURING THE PERIOD WITH PHX LIKELY SEEING LOWS IN THE 90S /RECORD HIGH MINS DEFINITELY POSSIBLE/. STILL LOOKING LIKE THIS COULD TURN OUT TO BE THE HOTTEST STRETCH OF TEMPS THIS YEAR AND CURRENT FORECAST DOES BRING TEMPERATURES TO NEAR-RECORD TERRITORY. MAX AND MIN TEMPS WILL BE AT OR ABOVE EXCESSIVE HEAT CRITERIA FRIDAY THROUGH SUNDAY SO WARNINGS WILL LIKELY BE ISSUED CLOSER TO THE EVENT. WILL BE A MORE STRONGLY WORDED HWO LATER THIS MORNING INDICATING HOW HOT WE/RE EXPECTING IT TO GET. TAIL-END OF THE WEEKEND AND INTO EARLY NEXT WEEK...THOUGH A BIT BEYOND OUR FORECAST TIME FRAME...GFS AND ECMWF HAVE BEEN CONSISTENTLY SHOWING AN WESTERLY TRAVELING WAVE COMING ACROSS NORTHERN MEXICO. THIS TYPE OF PATTERN/SETUP IS VERY CONDUCIVE TO THUNDERSTORM ACTIVITY ACROSS ARIZONA. THOUGH THE TIMING AND STRENGTH OF THIS FEATURE HAVE BEEN VARYING QUITE A BIT IT IS POSSIBLE THAT AFTER SOME BIG HEAT OVER THE WEEKEND WE/LL GET A SUDDEN RETURN TO CONVECTIVE ACTIVITY EARLY NEXT WEEK /WHICH IS OFTEN HOW IT WORKS/. WORTH KEEPING AN EYE ON. && .AVIATION... NO AVIATION WEATHER CONCERNS THRU AT LEAST 12Z TUESDAY. SFC WINDS AT KPHX HAVE VEERED AROUND TO THE SOUTHWEST...A BIT SOONER THAN EXPECTED. THIS WAS ASSOCIATED WITH A WEAK GULF SURGE THAT WAS MOST EVIDENT BY LOOKING AT WINDS/DEW POINTS AROUND THE LOWER DESERTS. FOR EXAMPLE YUMA HAD GUSTY WINDS TO 20 KTS AND DEW POINTS TO 67F. WINDS AT SKY HARBOR LIKELY TO SWITCH TO EASTERLY...AND SOME MID LEVEL DEBRIS CLOUDS COULD SEEP INTO THE EAST VALLEY AFT 08Z. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... WEDNESDAY THROUGH SUNDAY... UPPER RIDGE WILL BE SHIFTING BACK TO OUR E DURING THE EXTENDED... AND ALSO BUILDING STRONGLY AS IT DOES SO. THIS WILL RESULT IN A SIGNIFICANT WARMING TREND BY THE END OF THE WEEK...WITH HOTTEST DESERT HIGHS APPROACHING 118 DEG F BY FRIDAY OR SATURDAY. MINIMUM RELATIVE HUMIDITIES WILL OF COURSE DROP TO LESS THAN 15 PCNT MOST PLACES...BUT ONLY LIGHT WINDS EXPECTED FOR THE MOST PART. A SLIGHT CHANCE OF AFTN TSTMS STILL ON TAP OVER HIGHER TERRAIN OF FIRE WX ZONE 133...WHICH REPRESENTS ABOUT THE ONLY FIRE WEATHER CONCERNS UPCOMING THIS WEEK. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT WEATHER.GOV/PHOENIX DISCUSSION...MEYERS/INIGUEZ AVIATION...SIPPLE FIRE WEATHER...ESTLE