027
FXUS65 KPSR 052334
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
434 PM MST MON JAN 5 2026
UPDATE
00Z AVIATION DISCUSSION.
KEY MESSAGES
- SLIGHTLY ABOVE NORMAL TEMPERATURES WILL PERSIST THROUGH TUESDAY
BEFORE COOLING DOWN TO NEAR TO SLIGHTLY BELOW NORMAL LEVELS BY
THE LATTER HALF OF THE WEEK.
- A COUPLE OF WEATHER SYSTEMS WILL BRING A PERIOD OF UNSETTLED
CONDITIONS DURING THE MIDDLE PORTION OF THE WEEK, INCREASING
RAIN CHANCES OVER SOUTH-CENTRAL ARIZONA.
SHORT TERM /TODAY THROUGH TUESDAY/
THE LATEST OBJECTIVE ANALYSIS REVEALS THE DESERT SOUTHWEST
ENTRENCHED UNDER SOUTHWESTERLY FLOW ALOFT IN BETWEEN A LONGWAVE
TROUGH NEAR THE WEST COAST AND A RIDGE OF HIGH PRESSURE OVER THE
GULF COAST REGION. THE TROUGH OVER THE WEST COAST WILL CONTINUE TO
EXTEND SOUTHWARD AND BECOME A CUTOFF LOW OFF THE SOUTHERN CA
COAST BY TUESDAY BEFORE EJECTING EASTWARD JUST SOUTH OF THE REGION
BY MIDWEEK. OTHERWISE, WITH THE REGION UNDER SOUTHWESTERLY FLOW
ALOFT AND 500 MB HEIGHT FIELDS RANGING BETWEEN 568-574DM THROUGH
TUESDAY, SLIGHTLY ABOVE NORMAL TEMPERATURES WILL CONTINUE AS
AFTERNOON HIGHS HOVER RIGHT AROUND 70 DEGREES ACROSS THE LOWER
DESERTS. PERIODS OF MID TO HIGH-LEVEL CLOUDS ORIGINATING FROM THE
UPSTREAM TROUGH WILL CONTINUE TO MAINTAIN OVERNIGHT LOW
TEMPERATURES QUITE MILD FOR EARLY JANUARY AS READINGS BOTTOM OUT
IN THE LOW TO MID 50S ACROSS THE LOWER ELEVATIONS AND IN THE 40S
ACROSS THE HIGHER TERRAIN AREAS.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
THE AFOREMENTIONED CUTOFF LOW WILL QUICKLY MIGRATE INLAND FROM
THE NORTHERN BAJA COAST THROUGH NORTHERN SONORA ON WEDNESDAY,
BEFORE EJECTING EASTWARD AS AN OPEN WAVE INTO THE SOUTHERN PLAINS
BY THURSDAY. WITH THE EXCEPTION OF A FEW STRAGGLING OUTLIERS,
ENSEMBLE MEMBERSHIP REMAINS IN GOOD AGREEMENT SHOWING THE MAIN PV
ANOMALY AND COLD CORE REMAINING OVER NORTHERN SONORA WITH
FAVORABLE MOIST ASCENT INITIALLY RELEGATED TO SOUTHERN ARIZONA.
SUFFICIENT EVIDENCE EXISTS SUGGESTING THETA-E ADVECTION SPREADING
NORTH INTO SOUTH-CENTRAL ARIZONA TO MAINTAIN POPS WEDNESDAY. WHILE
LIKELY A LOW QPF EVENT, FORECAST BUFR SOUNDINGS INDICATE A
PROLONGED PERIOD OF DEEP SATURATION, FAVORING AREAS OF LIGHT RAIN
WEDNESDAY AFTERNOON AND EVENING.
A CLASSIC WINTER, LA NINA-LIKE PATTERN EVOLUTION STILL APPEARS ON
TRACK THURSDAY WITH NORTHERN STREAM, NEGATIVELY TILTED PV DIGGING
INTO DEEPENING INLAND CYCLOGENESIS OVER THE PLAINS/MIDWEST. GROWING
MODEL CONSENSUS IS MATERIALIZING SHOWING A WELL DEFINED VORTICITY
CENTER CARVING OUT THE WESTERN PERIPHERY OF THE LONGWAVE TROUGH OVER
ARIZONA BEFORE EJECTING INTO THE HIGH PLAINS. TIMING APPEARS NEARLY
OPTIMAL FOR VORTICITY FORCED ASCENT ALONG THE LEADING EDGE OF THE
COLD CORE TO INITIATE SHOWERS ALONG THE RIM IN A STEEPENING LAPSE
RATE ENVIRONMENT. THIS SCENARIO WOULD ALLOW MAINTENANCE OF SHOWERS
INTO LOWER ELEVATIONS AROUND AND EAST OF THE PHOENIX METRO WHERE
MARGINALLY UNSTABLE CONDITIONS COULD COMBINE WITH THE VORTICITY
FORCING. OTHERWISE, AS SOMEWHAT LOWER MIDLEVEL HEIGHTS LEAK INTO THE
REGION DURING THE LATTER HALF OF THE WEEK, CONFIDENCE IS GOOD THAT
TEMPERATURES WILL COOL DOWN TO NEAR TO SLIGHTLY BELOW NORMAL
BEFORE RESUMING A WARMING TREND OVER THE WEEKEND AS HIGH PRESSURE
RIDGING AND BLOCKED FLOW DEVELOP.
AVIATION
UPDATED AT 2335Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
NO AVIATION CONCERNS ARE EXPECTED THROUGH THE TAF PERIOD. WINDS
WILL CONTINUE TO FAVOR A WESTERLY DIRECTION THIS EVENING BEFORE
SWITCHING BACK OUT OF THE EAST AT KPHX AND KIWA AROUND MIDNIGHT.
ANY LINGERING LOW CLOUDS WILL DISSIPATE AFTER SUNSET, HOWEVER
SCT-BKN MID TO HIGH CLOUDS WILL PERSIST OVER THE REGION TONIGHT.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO AVIATION CONCERNS WILL EXIST THROUGH THE FORECAST PERIOD. WINDS
WILL FAVOR A W COMPONENT AT KIPL AND W-NW AT KBLH. PERIODS OF CALM
AND VRB WINDS WILL ALSO BE LIKELY AT BOTH TERMINALS. THICK MID TO
HIGH CLOUDS WILL CONTINUE TO SPREAD OVER THE REGION WITH SOME FEW
TO SOMETIMES SCT BASES AROUND 7-8 KFT BEING OBSERVED AS WELL.
FIRE WEATHER
MOISTURE LEVELS WILL REMAIN ELEVATED THROUGH MUCH OF THE WEEK WITH
MINIMUM AFTERNOON HUMIDITY VALUES ONLY FALLING INTO A 40-60% RANGE,
ALTHOUGH BECOMING SOMEWHAT DRIER BY THE WEEKEND. THIS WILL FOLLOW
EXCELLENT OVERNIGHT RECOVERY GREATER THAN 75%. WINDS WILL BE FAIRLY
LIGHT MOST OF THE WEEK WITH DIRECTIONS FOLLOWING TYPICAL
DIURNAL/NOCTURNAL TRENDS, HOWEVER STRENGTHENING NORTH WINDS SHOULD
BEGIN GUSTING DOWN THE LOWER COLORADO RIVER VALLEY LATE IN THE WEEK.
A DRY WEATHER PATTERN DURING THE FIRST PART OF THE WEEK WILL BECOME
MORE UNSETTLED DURING THE MIDDLE OF THE WEEK, WITH THE BEST
CHANCES FOR WETTING RAINS ACROSS THE HIGHER TERRAIN AREAS NORTH
AND EAST OF PHOENIX.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...LOJERO
LONG TERM...18/LOJERO
AVIATION...SALERNO
FIRE WEATHER...18/LOJERO
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