707
FXUS65 KTWC 120951
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
251 AM MST WED NOV 12 2025
SYNOPSIS
HIGH TEMPERATURES WILL REMAIN 5 TO 10 DEGREES ABOVE
NORMAL THROUGH FRIDAY. A LOW PRESSURE SYSTEM IS THEN EXPECTED TO
IMPACT THE REGION THIS WEEKEND, BRINGING CHANCES FOR RAIN AND HIGH
ELEVATION MOUNTAIN SNOW, MUCH COOLER TEMPERATURES, AND BREEZY
CONDITIONS. UNSETTLED CONDITIONS ARE EXPECTED TO CONTINUE EARLY NEXT
WEEK ALONG WITH BELOW NORMAL TEMPERATURES.
DISCUSSION
A DIGGING TROUGH OVER THE EASTERN PACIFIC WILL CLOSE AND SLOWLY
APPROACH THE WEST COAST OVER THE NEXT 48 HOURS, WHILE DOWNSTREAM
A RIDGE AXIS CURRENTLY OVER THE DESERT SOUTHWEST WILL SHIFT EAST
AND GIVE WAY TO SOUTHWEST FLOW ALOFT. WHILE THIS TROUGH REMAINS
UPSTREAM OF SOUTHEASTERN ARIZONA, TEMPERATURES WILL REMAIN ABOVE
NORMAL AND AN INCREASING STREAM OF HIGH LEVEL CIRRUS WILL SPREAD
OVER THE REGION.
THE AFOREMENTIONED TROUGH, LIKELY BECOMING A CLOSED LOW OFF THE
CALIFORNIA COAST BY FRIDAY, POSES A HEFTY FORECAST CHALLENGE.
MODELS TYPICALLY STRUGGLE WITH CLOSED LOWS, OFTEN MAKING THEM TOO
PROGRESSIVE AND QUICK TO MOVE DOWNSTREAM. WITH THAT IN MIND IT'S
NO SURPRISE THIS LOW IS CAUSING MODEL RUN TO RUN INCONSISTENCIES
IN ITS ARRIVAL AND STRENGTH. MODEL RUNS OVER THE LAST 24-36 HOURS
HAVE BEEN SLOWER TO BRING THE LOW INTO SOUTHEASTERN ARIZONA, WITH
PRECIPITATION CHANCES IN THIS FORECAST PACKAGE NOW HELD OFF UNTIL
AT LEAST EARLY SATURDAY FOR WESTERN TO CENTRAL PORTIONS OF
ARIZONA. EVEN THAT MAY BE TOO FAST AS SOME 00Z DETERMINISTIC
MODELS NOW DELAY QPF IN SOUTHEASTERN ARIZONA UNTIL EARLY SUNDAY.
THERE REMAIN ENSEMBLE MEMBERS AND RECENT MODEL RUNS THAT DO BRING
THE UPPER LOW IN QUICKER ON SATURDAY BUT IT WOULDN'T BE A SHOCK
TO SEE THIS SYSTEM DELAY FURTHER. ON TOP OF THE ONSET UNCERTAINTY,
MODELS ARE ALSO STRUGGLING TO HANDLE THE DEPTH OF THE LOW AS IT
CROSSES THE REGION, WHICH WOULD HAVE IMPLICATIONS ON PRECIPITATION
AMOUNTS AND POTENTIAL MOUNTAIN SNOW. THERE REMAINS QUITE THE
SPREAD IN QPF ACROSS ENSEMBLE MEMBERS, WITH A RECENT DRIER TREND
AMONG MANY OF THEM. OVERALL THE MESSAGE REMAINS THAT THERE WILL
LIKELY BE SOME SORT OF COOL-DOWN WITH CHANCES FOR PRECIPITATION BY
THIS WEEKEND...BUT THERE REMAIN DETAILS TO BE WORKED OUT BEFORE
THEN.
NEXT WEEK LOOKS FAVORABLE FOR MEAN TROUGHING TO CONTINUE ACROSS
THE REGION WITH CPC OUTLOOKS LEANING WETTER AND COOLER.
AVIATION
SCT-BKN HIGH LEVEL CIRRUS THROUGH THE FORECAST PERIOD. SFC WINDS
LIGHT, TERRAIN DRIVEN, AND UNDER 10 KTS. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
LIGHT TERRAIN DRIVEN WINDS MAINLY UNDER 12 MPH
THROUGH WEDNESDAY WITH MINIMUM RELATIVE HUMIDITIES OF 12 TO 22
PERCENT. A LOW PRESSURE SYSTEM WILL LIKELY CROSS THE REGION BY
THIS WEEKEND, THOUGH RECENT TRENDS HAVE SHOWN A DELAY IN ITS
ARRIVAL. CURRENT FORECAST KEEPS FRIDAY WARMER AND DRIER THAN
PREVIOUSLY ADVERTISED WITH COOLER AND WETTER CONDITIONS ARRIVING
SATURDAY, THOUGH MAY BE DELAYED UNTIL SUNDAY IF THE SYSTEM
CONTINUES TO SLOW. WINDS WILL LIKELY INCREASE AND TURN SOUTHWEST
WITH THE ARRIVAL OF THE LOW.
TWC WATCHES/WARNINGS/ADVISORIES
NONE.
PUBLIC...EDWARDS
AVIATION...EDWARDS
FIRE WEATHER....EDWARDS
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