696
FXUS65 KPSR 062300
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
400 PM MST SUN SEP 6 2026
UPDATE
UPDATED AVIATION
KEY MESSAGES
- ASIDE FROM SOME LIGHT SHOWER ACTIVITY LINGERING ACROSS JOSHUA TREE
NATIONAL PARK THROUGH THIS AFTERNOON, MOSTLY DRY AND QUIET WEATHER
CONDITIONS ARE EXPECTED THROUGH THE FIRST HALF OF THIS WEEK.
- THUNDERSTORM CHANCES WILL START TO INCREASE ACROSS CENTRAL AND
EASTERN ARIZONA BY THE LATTER HALF OF THE WEEK.
- AS HIGH PRESSURE BUILDS OVER THE REGION, TEMPERATURES WILL HEAT UP
TO ABOVE NORMAL LEVELS THROUGH THE MIDDLE OF THE WEEK.
SHORT TERM /TODAY THROUGH TUESDAY/
LATEST WATER VAPOR SATELLITE IMAGERY AS WELL AS STREAMLINE ANALYSIS
REVEAL THE SUBTROPICAL HIGH PRESSURE CENTERED OVER THE SOUTHERN
PLAINS WHILE AN UPPER LEVEL TROUGH CONTINUES TO BE SITUATED ACROSS
THE PACIFIC NORTHWEST. THIS UPPER LEVEL TROUGH WILL FINALLY BEGIN TO
MIGRATE EAST NORTHEASTWARD LATER TODAY THROUGH MONDAY TOWARDS THE
INTERMOUNTAIN WEST AND INTO SOUTH-CENTRAL CANADA BY TUESDAY WHILE
WEAKENING IN THE PROCESS. AS IT DOES SO, IT WILL ALLOW THE
SUBTROPICAL RIDGE TO GRADUALLY BUILD WESTWARD INTO OUR NECK OF THE
WOODS DURING THE FIRST HALF OF THE UPCOMING WEEK.
A PLUME OF TROPICAL MOISTURE ORIGINATING FROM HURRICANE MARIE, WHICH
CONTINUES TO SPIN WELL WEST OF THE BAJA PENINSULA COAST, AND AN
UPPER-LEVEL JET STREAK OVER THE GREAT BASIN REGION ARE SUPPORTING AN
EXTENSIVE BAND OF LIGHT TO LOCALLY MODERATE RAINFALL WHICH EXTENDS
FROM THE SOUTHERN CA COAST EAST-NORTHEASTWARD TOWARDS THE MOHAVE
DESERT REGION. THE BULK OF THE ACTIVITY IS EXPECTED TO REMAIN OVER
THESE AREAS THROUGH THIS EVENING WITH JOSHUA TREE NATIONAL PARK
EXPECTED TO BE THE ONLY AREA WITHIN OUR CWA TO OBSERVE SOME LIGHT
RAINFALL ACTIVITY. WITH THIS LARGE CLUSTER OF RAINFALL, OUTFLOW
WINDS FROM THE NORTHWEST ARE EXPECTED TO IMPACT MUCH OF THE LOWER
DESERTS DURING THE AFTERNOON AND EVENING HOURS, WITH PEAK GUSTS OF
20-30 MPH LIKELY AS DEPICTED BY THE HI-RES GUIDANCE. AFTERNOON HIGH
TEMPERATURES WILL TOP OUT BETWEEN 102-106 DEGREES ACROSS THE SOUTH-
CENTRAL AZ LOWER DESERTS WITH SLIGHTLY COOLER READINGS BETWEEN 98-
105 DEGREES ACROSS THE WESTERN DESERTS DUE TO MORE CLOUD COVER.
CONDITIONS WILL REMAIN QUIET DURING THE FIRST HALF OF THE WEEK AS
THE OVERALL LACK OF INSTABILITY AND FORCING WILL HINDER STORM
ACTIVITY. THE BIGGER STORY WITH THE BUILDING RIDGE OF HIGH PRESSURE
WILL BE THE RISING TEMPERATURES. LATEST GUIDANCE SHOW 500 MB HEIGHTS
RISING FROM 590-593DM ON MONDAY TO 594-597DM BY EARLY WEDNESDAY,
WHICH IS NEAR RECORD STRENGTH FOR THIS TIME OF THE YEAR. AS A
RESULT, TEMPERATURES WILL GRADUALLY HEAT UP WITH THE LATEST NBM NOW
SHOWING LOWER DESERT HIGHS REACHING THE UPPER 100S TO SOME AREAS
APPROACHING 110 DEGREES BY TUESDAY AND LIKELY BE NEAR SIMILAR VALUES
THROUGH THE MIDDLE PORTION OF THE WEEK. THESE HIGH TEMPERATURES
COMBINED WITH EARLY MORNING LOWS IN THE MID TO UPPER 80S ARE LIKELY
TO CAUSE HEATRISK LEVELS TO REACH THE MAJOR CATEGORY, AND THUS IF
THESE TEMPERATURE TRENDS CONTINUE, EXTREME HEAT PRODUCTS WILL LIKELY
BE NEEDED FOR MUCH OF THE LOWER DESERTS IN THE SUBSEQUENT FORECAST
PACKAGES.
&
LONG TERM /WEDNESDAY THROUGH SATURDAY/
HEADING INTO THE LATTER HALF OF THE WORKWEEK, ENSEMBLE MODEL
GUIDANCE HAS COME INTO SLIGHTLY BETTER AGREEMENT ON THE OVERALL
SYNOPTIC PATTERN. THE MODELS HAVE COME INTO BETTER AGREEMENT ON THE
PLACEMENT OF THE FEATURES, BUT STILL DIFFER ON THE OVERALL STRENGTH
OF THE FEATURES. BOTH THE GEFS AND THE EPS SHOW A SHORTWAVE TROUGH
ACROSS THE NORTHERN CONUS AND SOUTHERN CANADA, A BROAD SUBTROPICAL
RIDGE STRETCHING ACROSS MUCH OF THE LOWER 2/3 OF CONUS, ALONG WITH A
CLOSED LOW OFF THE COAST OF NORTHERN CALIFORNIA. THE EPS CONTINUES
TO BE THE SLIGHTLY STRONGER SOLUTION, WITH A STRONGER CLOSED LOW IN
THE PACIFIC AND A SLIGHTLY STRONGER SUBTROPICAL HIGH. THIS OVERALL
BETTER AGREEMENT IS REFLECTED WITH THE SLIGHTLY SMALLER TEMPERATURE
SPREAD IN THE NBM INTERQUARTILE RANGE, WHICH HAS NARROWED TO LESS
THAN 5 DEGREES. THE GEFS SHOW THE HIGH AT PEAK STRENGTH (H5 HEIGHTS
OF 594-597 DM) ON WEDNESDAY BEFORE WEAKENING (H5 HEIGHTS OF 591-594
DM) BY THE LATTER HALF OF THE WEEK. THE HIGH LOOKS TO CONTINUE TO
WEAKEN (H5 HEIGHTS OF 588-592 DM) HEADING INTO THE WEEKEND.
THEREFORE, TEMPERATURES ARE FORECASTED TO REMAIN ABOUT 5 DEGREES
ABOVE NORMAL DURING THE MIDDLE OF THE WEEK BEFORE BEGINNING A SLIGHT
COOLING TREND FOR THE END OF THE WORKWEEK AND INTO THE WEEKEND
CLOSER TO NEAR NORMAL LEVELS.
AS FOR SHOWER AND STORM CHANCES, THE ENSEMBLE MEMBERS CONTINUE TO
SHOW THOSE CHANCES STARTING TO INCREASE, FOR AT LEAST PORTIONS OF
THE CWA, BEGINNING ON WEDNESDAY. PWATS LOOK TO INCREASE TO AROUND
1.5-1.9" FOR THE LATTER HALF OF THE WEEK, SO MOISTURE SHOULD NOT BE
A LIMITING FACTOR. WITH THE HIGH FORECASTED TO MOVE OVERHEAD, RAIN
CHANCES WILL LIKELY BE LIMITED TO THE HIGHER TERRAIN AREAS ACROSS
EASTERN ARIZONA ON WEDNESDAY AND THURSDAY. RAIN CHANCES MAY EXTEND
INTO THE LOWER DESERTS OF SOUTH-CENTRAL ARIZONA HEADING INTO THE
WEEKEND. HOWEVER, THE CURRENT WPC POPS OF 30-40%, FOR FRIDAY INTO
SATURDAY, SEEM RATHER AGGRESSIVE, ESPECIALLY THIS FAR OUT. WPC'S
SATURDAY POPS OF 10-30% SEEM MORE REASONABLE.
AVIATION
UPDATED AT 2300Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
A PERIOD OF GUSTY NW WINDS THIS EVENING WILL BE THE GREATEST WEATHER
IMPACT UNDER OCCASIONALLY THICK MID/HIGH CIGS. CONFIDENCE IS
MODERATE THAT A PROLONGED PERIOD OF NW GUSTS 20-30KT WILL BE COMMON
THROUGH THE EVENING BEFORE SLOWLY WEAKENING BY MIDNIGHT. THIS MAY
CREATE SOME LOFTED DUST ACROSS THE REGION AFFECTING SLANTWISE
VISIBILITY. SIMILAR TO THIS MORNING, WINDS WILL BE DELAYED MAKING
THE TYPICAL EASTERLY SWITCH, AND IN SOME CASES LIKE KPHX, MAY NEVER
TRULY COMPLETE THE TRANSITION. WINDS SHOULD BE NOTICEABLY WEAKER
MONDAY AFTERNOON.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
GUSTY WINDS WITH LOFTED DUST AND AREAS OF SFC VSBY RESTRICTION INTO
MVFR CATEGORY EARLY THIS EVENING WILL BE THE MAIN WEATHER ISSUE.
CONFIDENCE IS GOOD THAT THICK MID/HIGH CIGS WITH VIRGA/SPRINKLES
WILL PERSIST THROUGH OVERNIGHT WITH NORTHERLY GUSTS 25-35KT EARLY
THIS EVENING RAPIDLY WEAKENING BY MID EVENING. HOWEVER, LOFTED DUST
AND AREAS WITH SFC VSBY FALLING INTO MVFR CATEGORY WILL BE COMMON
FOR A FEW HOURS. OTHERWISE, A N/NW WIND COMPONENT WILL BE FAVORED
THROUGH MONDAY THOUGH PERIODS OF NEARLY CALM CONDITIONS WILL BECOME
MORE LIKELY.
FIRE WEATHER
TEMPERATURES WILL BE SLIGHTLY BELOW NORMAL ACROSS SE CA TODAY.
OTHERWISE, TEMPERATURES WILL WARM TO ABOVE NORMAL LEVELS THROUGH THE
MIDDLE OF THE WEEK. RAIN CHANCES TODAY WILL BE CONFINED TO JOSHUA
TREE NATIONAL PARK, WITH CHANCES FOR WETTING RAINFALL VERY LOW.
MINRH'S WILL GENERALLY BE AROUND 20-30% AREA WIDE THROUGH MUCH OF
THIS UPCOMING WEEK WITH GOOD OVERNIGHT RECOVERIES. SOME ELEVATED
AFTERNOON/EARLY EVENING BREEZINESS OUT OF THE NORTHWEST CAN BE
EXPECTED THIS AFTERNOON AND EVENING WITH PEAK GUSTS OF 20-30 MPH. A
MORE TYPICAL DIURNAL WIND PATTERN WITH SOME OCCASIONAL AFTERNOON
UPSLOPE BREEZINESS CAN BE EXPECTED THROUGH MUCH OF THIS COMING WEEK.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...LOJERO
LONG TERM...BERISLAVICH/LOJERO
AVIATION...18
FIRE WEATHER...LOJERO/BERISLAVICH
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