518
FXUS65 KPSR 181715
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1015 AM MST FRI SEP 18 2026
UPDATE
UPDATED AVIATION
KEY MESSAGES
- DRY AND TRANQUIL WEATHER CONDITIONS ARE EXPECTED THROUGH THIS
WEEKEND WITH NEAR ZERO RAIN CHANCES.
- NEAR TO SLIGHTLY ABOVE NORMAL TEMPERATURES ARE EXPECTED THROUGH
AT LEAST THIS WEEKEND WITH AFTERNOON TEMPERATURES NEAR 100 DEGREES
ACROSS THE LOWER DESERTS.
- A LOW PRESSURE SYSTEM AND MOISTURE RETURN EARLY NEXT WEEK WILL
BRING A RETURN OF RAIN CHANCES TO AT LEAST THE HIGH TERRAIN OF
NORTHERN AND EASTERN ARIZONA.
SHORT TERM /TODAY THROUGH SUNDAY/
DRYING CONDITIONS WITH NEAR TO SLIGHTLY ABOVE NORMAL TEMPERATURES
ARE EXPECTED TODAY THROUGH THIS WEEKEND. IT IS STILL MUGGY AT THE
SURFACE IN SOUTH-CENTRAL AZ, INCLUDING PHOENIX, WITH DEW POINT
TEMPERATURES IN THE 60S TO NEAR 70 DEGREES EARLY THIS MORNING, BUT
DRY AIR HAS MOVED IN ALOFT, WHICH IS PARTLY WHY THERE WERE NO
ADDITION SHOWERS AND STORMS THURSDAY AFTER THE VERY WET WEDNESDAY.
PWATS AT MIDNIGHT YESTERDAY WERE AROUND 1.7-1.9", BUT HAVE SINCE
DROPPED TO 1.0-1.2" AND WILL CONTINUE FALLING TODAY THROUGH
SATURDAY. SURFACE MOISTURE WILL ALSO STEADILY SCOUR OUT TODAY
THROUGH SATURDAY, FALLING INTO THE 50S BY THIS EVENING AND INTO
THE 40S BY SATURDAY EVENING IN SOUTH-CENTRAL AZ. IT WILL BE EVEN
DRIER WEST OF PHOENIX. THE ABUNDANT DRY AIR THAT WILL BE MOVING
THROUGH CAN BE SEEN UPSTREAM ON WATER VAPOR SATELLITE IMAGERY.
SATELLITE ALSO SHOWS A SHORTWAVE MOVING THROUGH SOUTHEAST AZ, WHICH
MAY PROVIDE JUST ENOUGH FORCING TO SPARK ISOLATED SHOWERS AND STORMS
IN THE WHITE MTNS THIS MORNING AND EARLY THIS AFTERNOON, POSSIBLY
CLIPPING PORTIONS OF SOUTHEASTERN GILA COUNTY. THERE IS ALSO A BROAD
UPPER LEVEL LOW SITUATED OVER THE NORTHWEST CONUS. THIS LOW WILL
GRADUALLY TRACK EASTWARD THROUGH THIS WEEKEND AND HELP SUPPRESS H5
HEIGHTS OVER THE DESERT SOUTHWEST AND THUS MODERATING THE
TEMPERATURES. TEMPERATURES WILL BE NEARLY THE SAME EACH DAY, WITH
MORNING LOWS IN THE 70S AND AFTERNOON HIGHS AROUND 97-103 DEGREES
ACROSS THE LOWER DESERTS. NORMAL HIGHS ARE RIGHT AROUND 100 DEGREES
FOR MID-SEPTEMBER. THESE TEMPERATURES WILL BE A NICE REPRIEVE,
ESPECIALLY THE MORNINGS, BUT WILL STILL RESULT IN MINOR HEATRISK.
LONG TERM /MONDAY THROUGH THURSDAY/
HEADING INTO EARLY NEXT WEEK, THERE IS GOOD CONFIDENCE THAT A
PACIFIC LOW WILL MOVE TO THE CENTRAL/SOUTHERN COAST OF CALIFORNIA
BY THE END OF THE DAY MONDAY. EXACTLY HOW THIS LOW EVOLVES ONCE
REACHING THE COAST IS STILL A LITTLE UNCERTAIN, BUT LATEST MODEL
CONSENSUS SUGGESTS THE LOW WILL TRACK ENE INLAND STAYING MOSTLY
NORTH OF THE LOCAL AREA AND DRIVING A CHANCE FOR SHOWERS AND STORMS
ACROSS NORTHERN AZ. CONCEPTUALLY THIS IS NOT A BAD SETUP FOR A
TRANSITIONAL SEVERE WEATHER EVENT WITH POTENTIAL FRONTOGENETICAL
FORCING AND A MODERATELY STRONG UPPER LEVEL JET WITH HIGHER SHEAR,
BUT REBOUNDING QUICKLY FROM THE VERY DRY AIR THIS WEEKEND AND
GETTING SUFFICIENT MOISTURE IN HERE TO SUPPORT ANY LOWER DESERT RAIN
CHANCE WILL BE TOUGH. MODEL GUIDANCE DOES AT LEAST SUPPORT A SLOW
RETURN OF MOISTURE MONDAY THROUGH NEXT WEEK, MORE SO COMING FROM THE
SOUTHEAST LIKE TYPICAL EARLY STAGES OF THE MONSOON.
MODEL GUIDANCE IS ALSO POINTING TOWARD A STRONG RIDGE DEVELOPING
THROUGH THE MIDDLE OF THE U.S. WITH THE SUBTROPICAL HIGH
RESTRENGTHENING NEAR/OVER TEXAS BY MID TO LATE WEEK. THIS WOULD KEEP
THE DESERT SOUTHWEST UNDER PREDOMINANT SOUTHWEST FLOW WHICH IS NOT
THE MOST IDEAL SETUP FOR LOWER DESERT STORM CHANCES, ESPECIALLY NOT
FOR SOUTHEAST CA AND SOUTHWEST AZ. LATEST NBM FORECAST HAS POPS
FOCUSED PRIMARILY ACROSS NORTHERN AND EASTERN AZ EACH DAY NEXT WEEK
WITH ONLY MINOR (10-20%) POPS FOR SOUTH-CENTRAL AZ LOWER DESERTS IN
THE EVENINGS. THE ONE THING THIS PATTERN DOES OPEN THE DOOR FOR, THE
LONGER IT PERSISTS, IS POTENTIAL EASTERN PACIFIC TROPICAL MOISTURE
ADVECTING NORTH.
TEMPERATURES THROUGH NEXT WEEK WILL MOSTLY STAY THE SAME DAY-TO-DAY,
WITH HIGHS IN THE UPPER 90S TO LOWER 100S, WHICH WILL BE AROUND 2-5
DEGREES ABOVE NORMAL, AND LOWS REMAINING MOSTLY IN THE 70S. THE
TEMPERATURES WILL LEAD TO WIDESPREAD MINOR HEATRISK THROUGH AT LEAST
THE FIRST HALF OF THE WEEK WITH A TREND TOWARD AREAS OF MODERATE
HEATRISK BY THE SECOND HALF OF THE WEEK AS MORNING LOW TEMPERATURES
CREEP BACK UP.
AVIATION
UPDATED AT 1715Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
NO MAJOR WEATHER ISSUES WILL EXIST THROUGH SATURDAY AFTERNOON UNDER
A FEW MOUNTAIN CUMULUS BUILD-UPS AND PATCHY HIGH CIRRUS. CONFIDENCE
IS GOOD THAT EAST WINDS WILL ONLY GRADUALLY SWITCH TO WESTERLY
MID/LATE AFTERNOON WITH A PROLONGED PERIOD CENTERED AROUND A
SOUTHERLY CROSS RUNWAY TRAJECTORY (I.E. 140V230) WITH SPEEDS NEARING
10KT. A REVERSAL BACK TO EASTERLY IS NOT LIKELY UNTIL AFTER
MIDNIGHT.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO WEATHER ISSUES WILL EXIST THROUGH SATURDAY AFTERNOON UNDER CLEAR
SKIES. WINDS WILL FAVOR A W/NW DIRECTION AT KIPL AND S/SW
TRAJECTORY AT KBLH. SPEEDS SHOULD REMAIN UNDER 12KT WITH LIMITED
GUSTS, AND EXTENDED PERIODS NEARLY CALM CONDITIONS OR LIGHT
NORTHERLY IN THE MORNING.
FIRE WEATHER
OVERALL THERE ARE NO FIRE WEATHER CONCERNS THROUGH THE NEXT WEEK. A
DRYING TREND WILL CONTINUE TODAY THROUGH THIS WEEKEND. WITH NO RAIN
EXPECTED THROUGH AT LEAST THE START OF NEXT WEEK. MINIMUM RH VALUES
THIS AFTERNOON WILL BE AROUND 20-35% ACROSS SOUTH-CENTRAL AZ TO 10-
20% ACROSS SOUTHEAST CA AND SOUTHWEST AZ. THE MINIMUM RHS WILL THEN
DIP TO 10-20% FOR NEARLY ALL AREAS THIS WEEKEND. OVERNIGHT
RECOVERIES ACROSS SOUTH-CENTRAL AZ WILL STILL BE GOOD TONIGHT AT 45-
75%, BUT THEN FALLS LOWER THIS WEEKEND. THERE WILL BE A GRADUAL
RETURN OF MOISTURE NEXT WEEK, BEST ACROSS EASTERN AZ AND THERE WILL
BE AN INCREASE IN RAIN CHANCES AGAIN, BUT AS OF NOW RAIN CHANCES
LOOK TO PRIMARILY FAVOR NORTHERN AND EASTERN AZ HIGH TERRAIN.
BESIDES A POTENTIAL INCREASE IN BREEZINESS EARLY NEXT WEEK WITH A
WEATHER SYSTEM, WINDS WILL MOSTLY FOLLOW TYPICAL DIURNAL PATTERNS
WITH MODEST AFTERNOON UPSLOPE/UPVALLEY GUSTINESS (15-25 MPH).
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...BENEDICT
LONG TERM...BENEDICT
AVIATION...18
FIRE WEATHER...BENEDICT
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