338 FXUS65 KPSR 070459 AFDPSR AZZ020>028-CAZ030>033-071045- SOUTHWEST ARIZONA/SOUTHEAST CALIFORNIA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ 1000 PM MST SAT OCT 6 2001 .SYNOPSIS... LOW PRESSURE ALOFT WILL GIVE UNSETTLED WEATHER TO MAINLY SOUTH- CENTRAL ARIZONA...WITH SCATTERED TO NUMEROUS SHOWERS AND THUNDER- STORMS EXPECTED TO BE THE RULE INTO COLUMBUS DAY. MEANWHILE...FAR SOUTHWEST ARIZONA AND SOUTHEAST CALIFORNIA WILL SEE LIMITED SHOWER ACTIVITY...MAINLY TONIGHT AND INTO EARLY SUNDAY. TEMPERATURES WILL BE LOWERING TO BELOW NORMAL LEVELS THE NEXT FEW DAYS. ON TUESDAY ANOTHER UPPER LOW WILL BRING DRIER AND LOCALLY WINDY CONDITIONS TO THE REGION. ANOTHER LOW PRESSURE AREA MOVING BY TO OUR NORTH LATE IN THE WEEK WILL HELP TO REINFORCE THE DRY...COOL WEATHER INTO NEXT WEEKEND. .DISCUSSION... STRONG UPPER LOW CENTERED JUST SOUTHWEST OF SAN DIEGO AS OF 930 PM HAS BEGUN TO MOVE TOWARD THE EAST THIS EVENING. DYNAMICS ASSOCIATED WITH THIS LOW INTERACTED WITH DESTABILIZATION ASSOCIATED WITH SFC HEATING AND INCREASING LOW-LEVEL MOISTURE (P-WATER IN EXCESS OF 1 INCH AND SFC DEW POINTS IN THE MID 60S THIS EVENING) TO GENERATE SCATTERED THUNDERSTORMS OVER THE FORECAST AREA SATURDAY AFTN AND EVENING...WITH ISOLATED AREAS RECEIVING IN EXCESS OF ONE HALF INCH. ISSUED A SMALL STREAM FLOOD ADVISORY FOR CENTRAL LA PAZ COUNTY VALID UNTIL 1030 PM AFTER LOCALLY HEAVY RAIN FELL JUST EAST OF BOUSE AND CAUSED WASHES TO FLOOD OVER AND NEAR STATE ROUTE 72 EARLIER THIS EVENING. ALL SHORT RANGE NUMERICAL GUIDANCE TRACK THE SYSTEM SLOWLY EAST THE NEXT 24 HRS. SOLUTIONS VARY SOMEWHAT AMONGST MODELS...BUT AVN HAS HANDLED THIS SYSTEM MOST CONSISTENTLY AND ACCURATELY...AND IT HAS PLACED THE 500 MB CENTER OVER EXTREME SOUTHEAST CALIFORNIA AT 00Z MONDAY IN EACH OF THE PAST 3 MODEL RUNS. AXIS OF DEEPEST MOISTURE ALIGNED N-S OVER WESTERN AZ AND GULF OF CALIFORNIA ATTM...SO IT APPEARS MOSITURE AVAILABILITY WILL NOT BE A PROBLEM AS THE SYSTEM MOVES SLOWLY TOWARD AZ ON SUNDAY. UPPER DIVERGENCE PROGGED TO INCREASE OVER W-CNTRL AND S-CNTRL AZ SUNDAY AFTN AS UPPER JET STREAK TRACKS ENE JUST SOUTH OF THE INTERNATIONAL BORDER. NEARLY UNIDIRECTIONAL SSW WIND PROFILE EXPECTED OVER W-CNTRL AND S-CNTRL AZ SUNDAY...ALONG WITH INCREASING WINDS WITH HEIGHT...SO SOME BACKBUILDING STORMS ARE POSSIBLE...AND LOCALLY HEAVY RAINFALL WILL STILL BE POSSIBLE. ONLY MITIGATING FACTOR WILL BE COOLER DAYTIME HIGHS...WITH MAX TEMPS ONLY IN THE LOW OR MID 80S...BUT SOME COOLING IN MID LEVELS ASSOCIATED PRIMARILY WITH SYNOPTIC SCALE LIFT SHOULD HELP MAINTAIN DECENT LAPSE RATE. NO UPDATES THIS EVENING. DG .PSR...NONE.