945
FXUS65 KPSR 050815
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
115 AM MST MON JAN 5 2026
KEY MESSAGES
- TEMPERATURES WILL REMAIN SLIGHTLY ABOVE NORMAL FOR THE MAJORITY
OF THE WEEK WITH THE COOLEST READINGS MIDWEEK.
- A PERIOD OF UNSETTLED WEATHER WILL AFFECT PARTS OF SOUTH-CENTRAL
ARIZONA DURING THE MIDDLE OF THE WEEK WITH INCREASED CHANCES OF
LIGHT RAIN.
SHORT TERM /TODAY THROUGH TUESDAY/
LONGWAVE TROUGHING CONTINUES TO SLOWLY MIGRATE INTO THE WESTERN
CONUS DISPLACING AND DAMPENING HIGH PRESSURE RIDGING EASTWARD.
ENHANCED JET ENERGY AND DEEP SW FLOW OVER THE FORECAST AREA HAS
SUPPORTED EXPANSIVE CLOUD COVER WHILE INDIVIDUAL SHORTWAVES LIFT
NORTH OF THE REGION. AN ILL-DEFINED FRONT HAS PROGRESSED INLAND
TAPPING A NARROW CORRIDOR OF H8-H7 MOISTURE, ALBEIT MOSTLY TRAPPED
UNDER A MIDTROPOSPHERIC INVERSION. THIS SHALLOW LOW LEVEL MOISTURE
COMBINED WITH OROGRAPHIC FORCING MAY BE SUFFICIENT TO GENERATE A FEW
SHOWERS ACROSS THE UPSLOPE AREAS OF CENTRAL ARIZONA THROUGH THIS
MORNING, THOUGH WITH LITTLE TO NO ACCUMULATION. OTHERWISE, H5
HEIGHTS WILL RETREAT MODESTLY CLOSER TO A 568-574DM RANGE OVER THE
NEXT 48 HOURS ALLOWING TEMPERATURES TO COOL A COUPLE DEGREES FROM
PERSISTENCE, THOUGH STILL AT A SLIGHTLY ABOVE NORMAL LEVEL.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
SHORTWAVE ENERGY DROPPING SOUTH ALONG THE WEST COAST WILL DETACH
FROM THE NORTHERN STREAM FLOW AND CARVE OUT A TROUGH BASE OFF THE
SOUTHERN CALIFORNIA COAST THROUGH NORTHERN MEXICO WEDNESDAY AND
THURSDAY. WITH THE EXCEPTION OF A FEW STRAGGLING OUTLIERS, ENSEMBLE
MEMBERSHIP REMAINS IN GOOD AGREEMENT SHOWING THE MAIN PV ANOMALY AND
COLD CORE DIPPING INTO 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, SO A TREND TOWARDS LOCALLY HIGHER POPS AND MORE
EXTENSIVE COVERAGE OF LIGHT RAIN IN THE SOUTHERN CWA WOULD NOT BE
UNEXPECTED.
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 RETREAT A LITTLE CLOSER TO THE SEASONAL NORMAL
BEFORE RESUMING A WARMING TREND OVER THE WEEKEND AS HIGH PRESSURE
RIDGING AND BLOCKED FLOW DEVELOP.
AVIATION
UPDATED AT 0520Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
LOWER VFR CIGS AND THE POTENTIAL FOR BRIEF -SHRA CONDITIONS FOCUSED
EAST/NORTHEAST OF THE TERMINALS MONDAY MORNING WILL BE THE MAIN
WEATHER ISSUES DURING THE TAF PERIOD. WINDS WILL OVERALL REMAIN
LIGHT (AOB 6 KTS) AND FOLLOW DIURNAL TENDENCIES, HOWEVER, CONFIDENCE
IS LOWER THAN USUAL ON WIND DIRECTIONS OVERNIGHT AS A DECAYING FRONT
MOVES INTO THE REGION. WINDS MAY BECOME VRB OR BRIEFLY SWITCH WEST
OVERNIGHT, BUT AGAIN, SHOULD REMAIN LIGHT. CIGS AROUND 5-6 KFT AGL
WILL BE MOST LIKELY BETWEEN 09-16Z AND WILL BE FOCUSED OVER THE
EASTERN HALF OF THE AIRSPACE MONDAY MORNING. OTHERWISE, ANTICIPATE
PERIODS WITH FEW-SCT DECKS BETWEEN 4-7 KFT AGL AND OCCASIONAL
THICKER CIRRUS DECKS STREAMING OVER THE REGION.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO MAJOR WEATHER ISSUES WILL EXIST THROUGH THE NEXT 24 HOURS UNDER
PERIODS OF FEW-SCT DECKS BETWEEN 5-8 KFT AGL AND OCCASIONAL THICKER
CIRRUS DECKS. CONFIDENCE IN THE WIND FORECAST IS LOWER THAN USUAL,
HOWEVER, SW/W DIRECTIONS SHOULD BE FAVORED AND SPEEDS SHOULD
GENERALLY REMAIN AOB 10 KTS. A PERIOD OF VRB WINDS IS LIKELY
BEGINNING MONDAY MORNING AT BOTH TERMINALS. BY THE AFTERNOON,
CONFIDENCE IS GOOD THAT SOUTHWEST WINDS WILL INCREASE AT KBLH WITH
OCCASIONAL GUSTS INTO THE TEENS. LATER IN THE AFTERNOON, CONFIDENCE
IS MODERATE THAT WEST WINDS WILL TEMPORARILY INCREASE AT KIPL WITH
OCCASIONAL GUSTS INTO THE TEENS.
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, HOWEVER CHANCES FOR
WETTING RAINFALL APPEAR VERY LIMITED.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...18
LONG TERM...18
AVIATION...WHITTOCK
FIRE WEATHER...18
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