845
FXUS65 KPSR 182300
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
400 PM MST THU DEC 18 2025
KEY MESSAGES
- DRY AND TRANQUIL WEATHER CONDITIONS WITH WELLABOVE NORMAL
TEMPERATURES WILL PREVAIL ACROSS THE REGION THROUGH EARLY NEXT WEEK.
- A CHANGE IN THE WEATHER PATTERN IS EXPECTED LATER NEXT WEEK WITH
COOLER TEMPERATURES AND POTENTIALLY INCREASED PRECIPITATION CHANCES.
SHORT TERM /TODAY THROUGH FRIDAY/
UNSEASONABLY WARM WEATHER AND DRY, TRANQUIL CONDITIONS CONTINUE AS
STRONG UPPER LEVEL RIDGING PERSISTS ACROSS THE DESERT SOUTHWEST.
EARLY AFTERNOON RAP ANALYSIS SHOWED THE CENTER OF THE RIDGE OF HIGH
PRESSURE POSITIONED WEST OF THE BAJA PENINSULA WITH 500 MB HEIGHTS
ACROSS THE FORECAST AREA AROUND 582-585 DM. AS THE UPPER LEVEL RIDGE
GRADUALLY SHIFTS EASTWARD, HEIGHTS WILL RISE SLIGHTLY FOR FRIDAY,
PROMOTING A WARMER AFTERNOON TO END THE WORKWEEK. AFTERNOON HIGHS
FRIDAY ACROSS SOUTH-CENTRAL AND SOUTHWEST ARIZONA ARE FORECAST TO
TOP OUT 2-3 DEGREES WARMER THAN TODAY AS TEMPERATURES CLIMB INTO THE
UPPER 70S TO AROUND 80 DEGREES, WITH SIMILAR READINGS EXPECTED
ACROSS SOUTHEAST CALIFORNIA. AFTERNOON TEMPERATURES READING AROUND
10-15 DEGREES ABOVE NORMAL WILL CONTINUE INTO THE WEEKEND.
LONG TERM /SATURDAY THROUGH LATE NEXT WEEK/
UPPER-LEVEL RIDGING WILL CONTINUE TO PERSIST ACROSS THE DESERT
SOUTHWEST THROUGHOUT THE WEEKEND AND EARLY NEXT WEEK, CONTINUING THE
DRY AND TRANQUIL WEATHER PATTERN. TEMPERATURES WILL CONTINUE TO
REMAIN UNSEASONABLY WARM THROUGHOUT THIS PERIOD WITH AFTERNOON HIGHS
ACROSS THE LOWER DESERTS RANGING BETWEEN THE UPPER 70S TO LOW 80S,
WHICH WILL BE A GOOD 10-15 DEGREES ABOVE NORMAL FOR THIS TIME OF THE
YEAR. IN FACT, THERE IS A HIGH PROBABILITY (>70%) OF PHOENIX
BREAKING RECORD HIGHS, ESPECIALLY BY SUNDAY AND MONDAY, ACCORDING TO
THE LATEST NBM.
MODEL GUIDANCE CONTINUES TO SHOW A PATTERN CHANGE HEADING TOWARDS
THE MIDDLE AND LATTER PORTION OF NEXT WEEK AS THE UPPER-LEVEL RIDGE
MOVES EASTWARD INTO THE SOUTHERN PLAINS, ALLOWING A DEEP PACIFIC
TROUGH TO BUILD OFF THE WEST COAST. EXAMINING THE ENSEMBLE CLUSTER
ANALYSIS, THERE CONTINUES TO BE LARGE SPREAD IN THE OVERALL STRENGTH
AND POSITIONING OF THE TROUGH. NEVERTHELESS, THE ENSEMBLES SHOW
ABUNDANT MOISTURE SPREADING INTO THE REGION OUT AHEAD OF THE
TROUGHING FEATURE LATE TUESDAY INTO WEDNESDAY WITH IVT VALUES
FORECAST TO EXCEED 250 KG/M/S. THIS INCREASING MOISTURE WILL PROMOTE
PRECIPITATION CHANCES BEGINNING NEXT WEDNESDAY, WITH THE HIGHEST
CHANCES ACROSS THE WESTERN DESERTS. PRECIPITATION CHANCES MAY
CONTINUE THROUGH THE END OF NEXT WEEK, HOWEVER, THIS WILL ALL BE
DEPENDENT ON THE OVERALL STRENGTH AND POSITIONING OF THE TROUGH.
GIVEN THAT THIS WILL BE A WARM WEATHER SYSTEM, ALL OF THE
PRECIPITATION, EVEN ACROSS THE HIGHER TERRAIN, SHOULD FALL AS RAIN.
WITH THE INCREASING CLOUDS AND PRECIPITATION CHANCES, ALONG WITH
DECREASING HEIGHTS ALOFT, TEMPERATURES MID TO LATE NEXT WEEK ARE
EXPECTED TO COOL DOWN BUT WILL LIKELY STILL REMAIN ABOVE NORMAL.
AVIATION
UPDATED AT 2300Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT; AND
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO WEATHER ISSUES WILL EXIST THROUGH FRIDAY EVENING UNDER PERIODS OF
HIGH CIRRUS DECKS. WIND SPEEDS WILL REMAIN EXTREMELY LIGHT WITH ONLY
SUBTLE DIURNAL/NOCTURNAL DIRECTIONAL SHIFTS. EXTENDED PERIODS OF
VARIABLE DIRECTIONS AND CALM CONDITIONS WILL BE COMMON.
FIRE WEATHER
PERSISTENT HIGH PRESSURE ACROSS THE REGION WILL CONTINUE TO PROMOTE
DRY AND TRANQUIL WEATHER AS WELL AS UNSEASONABLY WARM TEMPERATURES,
10 TO 15 DEGREES ABOVE NORMAL, INTO EARLY NEXT WEEK. WINDS WILL
GENERALLY BE LIGHT AND FOLLOW FAMILIAR DIURNAL PATTERNS. AFTERNOON
MINRHS WILL RANGE BETWEEN 20-30% WITH GOOD OVERNIGHT RECOVERIES OF
40-70%.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...SMITH
LONG TERM...LOJERO
AVIATION...18
FIRE WEATHER...LOJERO/KUHLMAN
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