[Printable]
660 FXUS65 KPSR 040315 AFDPSR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ 815 PM MST SUN MAR 3 2013 .SYNOPSIS... A WEAK WEATHER DISTURBANCE WILL MOVE THROUGH NORTHERN ARIZONA TODAY BRINGING EXTENSIVE CLOUD COVER AND SLIGHTLY COOLER TEMPERATURES TO THE REGION. PRECIPITATION CHANCES WILL BE CONFINED MAINLY TO THE HIGHER TERRAIN OF NORTHERN ARIZONA...WITH ONLY A CHANCE FOR A BRIEF SPRINKLE FURTHER SOUTH. TEMPERATURES WILL REBOUND DURING THE MIDWEEK TIME FRAME...HOWEVER A MORE SIGNIFICANT COOLING TREND WILL DEVELOP DURING THE LATTER HALF OF THE WEEK AS LOW PRESSURE SETTLES OVER THE WESTERN STATES. THIS WEATHER SYSTEM WILL ALSO LEAD TO INCREASED PRECIPITATION CHANCES NEXT WEEKEND. && .DISCUSSION... CONSIDERABLE MID AND HIGH CLOUDS...ASSOCIATED WITH A WEAK WEATHER DISTURBANCE MOVING THROUGH SOUTHERN UTAH AND NORTHERN AZ...CONTINUED TO STREAM WEST TO EAST ACROSS AZ AT 03Z. A FEW SPRINKLES...BUT MOSTLY VIRGA SHOWERS...WERE NOTED ON RADAR SUNDAY AFTERNOON...WITH A FEW LINGERING SPRINKLES THIS EVENING IN THE PHOENIX AREA. AS THE DISTURBANCE MOVED QUICKLY EAST...CLEARING SKIES WERE NOTED IN SOUTHEAST CA AND SOUTHWEST AZ AT 03Z...WITH CLEARING EXPECTED IN CENTRAL AZ INCLUDING PHOENIX AREA BY 07Z. INCREASING WESTERLY FLOW ALOFT WILL CONTINUE TO SEND A SERIES OF PACIFIC DISTURBANCES INTO THE WESTERN STATES MAINLY NORTH OF AZ. ANOTHER ROUND OF MID AND HIGH CLOUDS ARE EXPECTED TUESDAY AFTERNOON AND NIGHT. OTHERWISE DRY WEATHER WITH ABOVE NORMAL TEMPERATURES WILL CONTINUE OVER THE REGION THROUGH TUESDAY. CURRENT FORECASTS LOOK OK. NO UPDATES PLANNED. PREVIOUS DISCUSSION BELOW WITH A FEW EDITS STILL APPLY. PORTIONS OF PREVIOUS DISCUSSION... CONSIDERABLE AMOUNT OF HIGH LEVEL CLOUDS STREAMED ACROSS THE SOUTHWEST DESERT REGION SUNDAY AFTERNOON...AS A SHORT WAVE MOVED INLAND. GREATEST WEATHER IMPACT THIS EVENING...OTHER THAN A FEW SPRINKLES... APPEARS TO BE LOCALLY BREEZY CONDITIONS OVER PARTS OF SOUTHEAST CALIFORNIA WITH THE PASSAGE OF A DISORGANIZED COLD FRONT. DIMINISHING WIND IN SOUTHEAST CA...WHICH EARLIER PEAKED TO 32 MPH AT IMPERIAL CA AND 24 MPH AT BLYTHE CA AT 01Z...IS EXPECTED TO DIMINISH THE REMAINDER OF THE EVENING. THE SHORTWAVE TROUGH AXIS WILL PASS THROUGH THE REGION MONDAY...AND ALTHOUGH HEIGHTS ALOFT WILL CHANGE LITTLE...MODEL TRENDS ARE LEANING TOWARDS STRONGER CAA WITHIN THE MIXED BOUNDARY LAYER. THIS TENDENCY IS REFLECTED IN MODEL GUIDANCE TEMPERATURES SEVERAL DEGREES LOWER THAN PREVIOUS ITERATIONS...AND HAVE FOLLOWED SUIT CUTTING JUST UNDER THE MEDIAN OF ALL AVAILABLE GUIDANCE. RATHER TRANQUIL WEATHER WILL FOLLOW INTO THE MIDWEEK PERIOD WITH SHORTWAVE RIDGING CHARACTERIZED BY H5 HEIGHTS IN A 570-573DM RANGE SITUATED OVER THE AREA. USED A GENERAL MODEL BLEND WITH RESPECT TO TEMPERATURES...AND DEPENDING ON CLOUD COVER (OR LACK THEREOF) MAY NEED TO PUSH AFTERNOON HIGHS SLIGHTLY WARMER BASED ON HISTORICAL TRENDS. OPERATIONAL MODELS REMAIN VERY STEADY IN CONTINUITY...TIMING...AND TRENDS TOWARDS A SIMILAR SOLUTION FORECASTING A MODERATE NEGATIVE HEIGHT ANOMALY DIGGING INTO THE SWRN CONUS THOUGH THE END OF THE WEEK. DESPITE THIS APPARENT SIGNAL OF HIGHER CONFIDENCE...SPREAD AMONG ENSEMBLE MEMBERS (AND PARTICULARLY CMC MEMBERS) HAS ACTUALLY GROWN IN THE PAST SEVERAL RUNS...KEEPING A LARGER AMOUNT OF UNCERTAINTY IN THIS FORECAST PACKAGE. AND EVEN THE RELATIVELY MINOR TIMING AND POSITIONAL DIFFERENCES BETWEEN OPERATIONAL MEMBERS...AS THE CIRCULATION CENTER ATTEMPTS TO DISASSOCIATE WITH THE NORTHERN STREAM STEERING FLOW...LIMITS MORE FORECAST SPECIFICS AT THIS TIME. REGARDLESS...GIVEN THE PRESENCE OF A DEEPER SYSTEM ACROSS THE REGION SOMETIME DURING THIS TIME FRAME...HAVE KEPT POPS SPREAD OVER THE ERN CWA ABOVE CLIMATOLOGY...WHILE HEDGING TEMPERATURES MUCH BELOW AVERAGE AND TOWARDS BIAS CORRECTED RAW MODEL OUTPUT (AND EVEN THESE FORECASTS UP TO 10F BELOW NORMAL MAY NEED TO BE ADJUSTED DOWNWARD DEPENDING IN THE EXACT TIMING AND TRACK OF THE COLD CORE ALOFT). && .AVIATION... SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA AND KSDL... THROUGH 08Z MON...LIGHT WIND. BKN CLDS AOA 15 THSD AGL. 08Z MON THROUGH 20Z MON...SCT CLDS AOA 16 THSD AGL. LIGHT WIND. SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH... THROUGH 10Z MON...SCT CLOUDS AOA 15 THSD AGL. SOUTHWEST WIND 10 TO 15 KNOTS. FROM 10Z MON TO 20Z MON...SCT CLDS AOA 16 THSD AGL... SOUTHWEST WIND 5 TO 10 KNOTS. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... TUESDAY THROUGH SATURDAY... RIDGING WILL QUICKLY RETURN TO THE AREA BY TUESDAY...WARMING DAYTIME TEMPERATURES BACK ABOVE NORMAL HIGH AND GENERATING LIGHT WINDS FOR TUESDAY AND WEDNESDAY. MINIMUM HUMIDITY PERCENTAGES SHOULD IN THE MID TEENS FOR TUESDAY AND WEDNESDAY WITH GOOD TO EXCELLENT OVERNIGHT RECOVERIES. BY WEDNESDAY...THE RIDGE BREAKS DOWN WHILE WINDS ALOFT TURN SOUTHWESTERLY AS A LARGE AREA OF PACIFIC LOW PRESSURE BEGINS EXPAND DOWN THE WEST COAST. THIS SYSTEM WILL TRACK FURTHER TO SOUTH INTO OUR AREA AND IS BETTER ORGANIZED AS COMPARED TO THE WEAKER SYSTEM EARLIER IN THE WEEK. SHOWER ACTIVITY...MUCH COOLER TEMPERATURES AND INCREASING WINDS ARE POSSIBLE BY THE LATE WEEK AND HEADING INTO NEXT WEEKEND. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX DISCUSSION...VASQUEZ/MEYERS/MO AVIATION...VASQUEZ FIRE WEATHER...NOLTE
