941
FXUS65 KTWC 211000
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
300 AM MST WED JAN 21 2026
SYNOPSIS
HIGH PRESSURE ALONG THE WEST COAST WILL RESULT IN ABOVE
NORMAL HIGH TEMPERATURES AND DRY CONDITIONS THROUGH THURSDAY. A
LOW PRESSURE SYSTEM MOVING INTO SOUTHEAST ARIZONA FROM THE EASTERN
PACIFIC WILL BRING A GOOD CHANCE FOR VALLEY RAIN AND MOUNTAIN
SNOW FRIDAY INTO THE WEEKEND.
DISCUSSION
SATELLITE IMAGERY THIS MORNING SHOWED SCATTERED HIGH
LEVEL CLOUDS MOVING ACROSS THE AREA WITH UPPER RIDGE AXIS CURRENTLY
SITUATED OVER SRN CA/BAJA CA. THIS RIDGE AXIS WILL MOVE EAST INTO
THE STATE TODAY WHILE FLATTENING, WHICH WILL ALLOW THE AREA OF
MAINLY MID TO HIGH LEVEL CLOUDS WEST OF SRN CA/BAJA CA TO
OVERSPREAD THE AREA THIS AFTERNOON. HIGHS TODAY SIMILAR TO YDAY.
EARLY MORNING WATER VAPOR IMAGERY THIS MORNING SHOWED A WEATHER
SYSTEM SLOWLY STRENGTHENING A LITTLE OVER 400 MILES WEST OF SAN
FRANCISCO. THIS FEATURE, WHICH WILL BE OUR WEATHER MAKER LATE
THURSDAY INTO THE WEEKEND, WILL BECOME A CUT-OFF LOW LATER THIS
MORNING INTO EARLY THIS AFTERNOON OFF THE CNTRL CA COAST THEN
MOVE SSE TO OFF THE SRN CA COAST BY THURSDAY AFTERNOON.
PRETTY DRY OVER THE AREA THIS MORNING WITH PW VALUES BETWEEN 0.10"
AND 0.20" BUT THAT WILL BE CHANGING OVER THE NEXT 36 TO 48 HOURS
WILL PW VALUES INCREASING BETWEEN 0.40" TO 0.70". WE'LL WASTE A
LOT BY MOISTENING UP FROM TOP DOWN BUT MAYBE QUICK ENOUGH FOR A
FEW VERY LIGHT SHOWERS DEVELOPING LATE THURSDAY AFTERNOON SE OF
TUCSON AND INTO THE EVENING HOURS FROM TUCSON SOUTH. THEREAFTER
THERE STILL IS SOME UNCERTAINTY ON TIMING OF MORE WIDESPREAD
SHOWERS THURSDAY NIGHT INTO FRIDAY MORNING. AT THIS TIME, I DIDN'T
DEVIATE FROM NBM INITIALIZED FORECAST WHICH HAD POPS IN THE
50-80% RANGE THU NGT/FRI AM. THIS MAY CHANGE OVER THE NEXT 24 HRS.
MAIN EVENT TIMING CONTINUES TO BE FRIDAY AFTERNOON INTO SUNDAY
MORNING AS THE UPPER LOW OPENS UP INTO A TROF AND SWINGS ACROSS
THE AREA ON SATURDAY WITH FOLLOW-UP SYSTEM DROPPING IN FROM THE
NORTH WITH COLDER AIR ASSOCIATED WITH IT ON SUNDAY. STILL PLENTY
OF DETAILS TO IRON OUT ESPECIALLY WITH RESPECTS TO LIQUID AND
FROZEN PRECIP AMOUNTS.
ON THE LIQUID SIDE, THERE REMAINS A LARGE SPREAD IN THE ENSEMBLE
3-DAY QPF VALUES ACROSS THE AREA WITH ENS/AIFS MUCH WETTER THAN
GEFS/AIGEFS. CURRENT 3-DAY RAINFALL AMOUNTS FROM WPC ARE UP FROM
24 HOURS AGO WITH VALLEY TOTALS RANGING FROM 0.20" WEST TO NEAR
1" SOUTH AND EAST OF TUCSON AND BETWEEN 1" & 2" IN THE MOUNTAINS.
ON THE SNOW SIDE, INITIAL SNOW LEVELS WILL BE RATHER HIGH THU
NIGHT INTO FRIDAY MORNING WITH SLOPPY ACCUMULATIONS WITH BETTER
STICKING AND ACCUMULATING SNOW FRIDAY AFTERNOON INTO SUNDAY
MORNING. CURRENT SNOW AMOUNTS ABOVE 7000 FEET, SPREAD OUT OVER A
2-DAY PERIOD, RANGE FROM 6"-12" WITH LOCALLY HIGHER AMOUNTS.
THESE TOTALS LIKELY TO CHANGE OVER THE NEXT 24 HOURS. TOO EARLY
FOR A WINTER STORM WATCH BUT ONE LIKELY WILL BE NEEDED.
WITH THE 2ND COLDER SYSTEM MOVING THROUGH SUNDAY, THERE IS THE
POTENTIAL, ALTHOUGH SLIM, FOR SOME LIGHT SNOW SHOWERS FOR THE
HIGHER VALLEYS EAST OF TUCSON SUNDAY MORNING.
HIGH TEMPERATURES 5 TO 10 DEGREES BELOW NORMAL THIS WEEKEND
BEFORE WARMING UP EARLY NEXT WEEK AS THE AREA DRIES OUT.
AVIATION
VALID THROUGH 22/12Z.
SCT LYRD CLOUDS AOA 18K FT AGL WILL BE INCRG ACROSS THE AREA THRU
22/18Z THEN BKN IN CVRG THRU END OF VALID PD. SFC WIND LESS THAN
10 KTS, FAVORING A WLY/NWLY DIRECTION DURING THE AFTERNOON AND
EARLY EVENING HOURS AND VARIABLE IN DIRECTION AT OTHER TIMES.
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
HIGH PRESSURE ALOFT WILL RESULT IN ABOVE NORMAL
HIGH TEMPERATURES AND DRY CONDITIONS THROUGH THURSDAY. 20-FOOT
WINDS WILL BE LESS THAN 15 MPH AND TERRAIN DRIVEN. MINIMUM RHS
WILL BE IN THE 12-20 PERCENT AT ALL ELEVATIONS THROUGH THURSDAY,
WITH AN INCREASE OF 15-20 PERCENT ACROSS THE EASTERN HALF OF
SOUTHEAST ARIZONA BEGINNING FRIDAY. A LOW PRESSURE SYSTEM MOVING
INTO SOUTHEAST ARIZONA FROM THE EASTERN PACIFIC WILL RESULT IN A
GOOD CHANCE OF VALLEY RAIN AND MOUNTAIN SNOW ACROSS SOUTHEAST
ARIZONA STARTING LATE THURSDAY AND CONTINUING INTO THE WEEKEND,
ALONG WITH COOLER TEMPERATURES AND INCREASING MINIMUM RHS.
TWC WATCHES/WARNINGS/ADVISORIES
NONE.
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