000 FXUS65 KPSR 061001 AFDPSR AZZ020>028-CAZ030>033-061745- AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ 300 AM MST TUE JUL 6 2004 SOUTHWEST AND SOUTH-CENTRAL ARIZONA...AND SOUTHEAST CALIFORNIA FORECAST DISCUSSION .SYNOPSIS... BUILDING HIGH PRESSURE ACROSS THE REGION WILL RESULT IN WARMER TEMPERATURES THE NEXT COUPLE OF DAYS. ANOTHER LOW PRESSURE SYSTEM WILL DEVELOP OFF THE CALIFORNIA COAST BY MIDWEEK. THIS SYSTEM WILL PULL SOME MOISTURE...FROM MEXICO...NORTHWARD INTO THE DESERT SOUTHWEST...LEADING TO A SLIGHT CHANCE OF THUNDERSTORMS OVER THE SOUTH-CENTRAL ARIZONA HIGHER TERRAIN THURSDAY...FRIDAY...AND THE WEEKEND. && .DISCUSSION... RECENT CONVECTIVE RAINS OVER THE SIERRA MADRE MOUNTAINS OF MEXICO... JUST EAST FROM GUAYMAS TO MAZATLAN...HAVE PUSHED OUTFLOWS INTO THE GULF OF CA...AND HAVE QUICKLY MOISTENED UP THE LOWER ATMOSPHERE. CHECK IT OUT. THE 00Z TUE GUAYMAS SOUNDING IS NOW AT MONSOON LEVELS. UNFORTUNATELY THE INTERIOR SECTION OF NORTH CENTRAL MEXICO...AROUND CHIHUAHUA IS STILL DRY. IN OTHER WORDS..MOST OF THE SIGNIFICANT HUMIDITY WAS LOCATED IN A LARGE PLUME EXTENDING FROM GUAYMAS SOUTH/SOUTHEAST...AND SOUTHWESTWARD INTO THE PACIFIC. COULD SOME OF THIS GULF OF MEXICO MOISTURE DRIFT NORTH INTO AZ...GIVING SOME HUMIDITY RELIEF TO THE FIRE EFFORTS. YOU BET. AND HERES WHY. WHATS GOING TO HELP THIS EFFORT IS THE CURRENT TROF DEVELOPING 550 MILES WEST OF SAN DIEGO. WATER VAPOR IMAGERY SHOWS THIS TROF BECOMING SLIGHTLY NEGATIVE TILT (JET MAX ON THE BACKSIDE)...HELPING TO SLOWLY BUILD A BROAD ANTI-CYCLONIC FLOW OVER THE SOUTHWEST U.S. AND...THIS ANTI-CYCLONIC FLOW WILL PHASE WITH THE HUGE MID/UPPER LEVEL ANTI-CYCLONE CENTERED NEAR THE SOUTHERN TIP OF BAJA. IN FACT ...00Z PLOT CHARTS WERE GIVING A HINT OF THIS AS 40 TO 60 METER 300 MB HEIGHT RISES WERE NOTED FROM NORTHWEST MEXICO SOLIDLY INTO THE GREAT BASIN AND SOUTHERN CALIFORNIA. AND...PERHAPS MOST IMPORTANT ...700 MB WINDS AT VANDENBERG AFB...SAN DIEGO... PHOENIX...AND TUCSON HAVE ALL BACKED FROM THE SOUTH AND SOUTHWEST. THE GFS MODEL WAS INITIALIZED SUPERBLY (THANKS TO THE N.A.M.E. PROJECTS WIDESPREAD MEXICAN RAOB COVERAGE DAY AND NIGHT). THE GFS FORECASTS INCREASING LOWER TROPOSPHERIC SOUTH FLOW INTO AZ FROM MEXICO...AND WE ASKED OURSELVES...BASED ON THE TUCSON SOUNDING (WITH NO MID LEVEL AIRMASS CHANGE)...WHAT MINIMUM MOISTURE VALUE IS NEEDED FOR AFTERNOON AND EVENING MOUNTAIN CONVECTION (7000 FEET). WE SETTLED ON A 700 MB DEWPOINT TEMPERATURE EQUAL OR GREATER TO ZERO DEGREES C. 700 MB DEWPOINT TEMPERATURES OVER CENTRAL AND SOUTHEAST AZ MONDAY AFTERNOON WERE IN THE MINUS 8 TO MINUS 16 DEGREE C RANGE (OUCH). HOWEVER BY WEDNESDAY AFTERNOON...THEY CREEP UP TO MINUS 2 TO ZERO C IN SOUTHEAST AZ...THEN TO ZERO TO PLUS 2 C OVER THE SOUTHEAST QUARTER OF THE STATE THU AFTERNOON. ADDITIONALLY...AND PERHAPS SIGNIFICANT...300/250 MB FLOWS BECOME INCREASINGLY DIFLUENT LATE WEDNESDAY AND THURSDAY AS THE OFFSHORE SAN DIEGO TROF MOVES INLAND. DIFLUENCE ALOFT SHIFTS INTO FAR SOUTHEAST AZ FRI AFTERNOON...WITH NEAR LAMINAR OR SLIGHTLY CONVERGENT FLOW (NOT TOO FAVORABLE FOR LARGE T-STORMS) SPREADING ACROSS THE REMAINDER OF THE STATE. THEREFORE THE FIRST LATE AFTERNOON CONVECTIVE STORMS SHOULD OCCUR OVER THE HIGHER TERRAIN OF SOUTHEAST AZ WEDNESDAY...FOLLOWED BY AN INCREASING CHANCE FOR CONVECTION OVER OUR MOUNTAINOUS ZONE 24 (OR EASTERN RIM TO THE WHITE MOUNTAINS) THURSDAY. THERE SHOULD BE ENOUGH HUMIDITY THURSDAY (ALTHOUGH THE AIRMASS WILL NOT BE AT MONSOON LEVELS YET) FOR A LITTLE DOUSING RAINFALL. WE WILL CONTINUE TO MENTION THE CHANCE FOR MOUNTAIN CONVECTION THROUGH THE WEEKEND. THE JUST IN CASE CLAUSE. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && 02