006
FXUS65 KTWC 172027
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
127 PM MST FRI OCT 17 2025
SYNOPSIS
BELOW NORMAL TEMPERATURES PREVAIL THE NEXT COUPLE OF
DAYS THEN TEMPERATURES WARM TO NEAR NORMAL SUNDAY INTO EARLY NEXT
WEEK. DRY CONDITIONS WILL ALSO PREVAIL THROUGH THE MIDDLE OF NEXT
WEEK.
DISCUSSION
SOUTHEAST ARIZONA HAS JUST ENOUGH RECYCLING LOW
LEVEL MOISTURE FOR SCATTERED CUMULUS CLOUDS TO FROM FROM SELLS
EASTWARD. SOME TOWERS ARE TRYING TO BUILD WHERE THERE IS MORE
FAVORABLE DYNAMICS AS A CURRENT SHORTWAVE PASSES THROUGH, BUT AS
SHOWN ON THE 18Z SOUNDING, THEY ARE STRUGGLING TO PASS THE WARM
AND DRY LAYER ABOVE IT. THIS SHORTWAVE TROUGH IS KEEPING THE AREA
5-8 DEGREES BELOW NORMAL HIGH TEMPERATURES TODAY AND TOMORROW.
ONCE THIS SHORTWAVE PASSES, THIS WILL CUT-OFF THE CURRENT LOW
PRESSURE SYSTEM THAT IS WEST OF NORTHERN BAJA. A RIDGE BEGINS TO
FORM OVER NORTHERN MEXICO. THIS HIGH PRESSURE WILL INCREASE HIGH
TEMPERATURES TO 3-5 DEGREES ABOVE NORMAL (CURRENT NORMAL IS 85-86
DEGREES FOR TUCSON), WITH THE HOTTEST DAY ON TUESDAY WHERE THE
CURRENT FORECAST HAS 90 DEGREES.
THE BIGGEST FORECASTING UNKNOWN IS IF AND HOW MUCH MOISTURE CAN BE
BROUGHT NORTHWARD INTO ARIZONA FROM THE EASTERN PACIFIC TUESDAY
INTO WEDNESDAY. DEPENDING ON WHERE THE CUT-OFF LOW SITS AND WHERE
THE PRESSURE GRADIENT CAN SET UP IS THANKS TO THE BUILDING RIDGE
TO THE EAST. THIS PATTERN WILL DETERMINE WHERE THE MOISTURE COULD
END UP. IF THE LOW STAYS MORE WEST, THEN MORE MOISTURE WILL STAY
CLOSER TO THAT LOW, KEEPING THE BEST MOISTURE TO FAR WESTERN PIMA
COUNTY. THIS IS THE CURRENT THOUGHT OF THE 12Z EMCWF MODEL. IF THE
LOW STAYS MORE EAST, THEN MORE MOISTURE WILL BRING A FAIR AMOUNT
OF MOISTURE TO MUCH OF SOUTHEASTERN ARIZONA. THIS IS THE CURRENT
THOUGHT OF THE GFS MODEL. BOTH SHOW AREAS OF 150-200% OF NORMAL
PWAT FOR THIS TIME OF YEAR, WHICH FOR OUR AREA WOULD TRANSLATE TO
ROUGHLY 0.7-1.2 INCHES OF PWAT. THE CURRENT FORECAST HAS SLIGHT
RAIN CHANCES (15-20%) ON TUESDAY/WEDNESDAY, BUT THIS MOISTURE IS
MORE LIKELY TO TRANSLATE INTO CLOUD COVER WITH LITTLE TO NO RAIN.
THERE IS STILL UNCERTAINTY WITH HOW THIS WILL UNFOLD, SO STAY
TUNED. THIS SYSTEM WILL COOL US DOWN TO NEAR NORMAL
TEMPERATURES MID TO LATE NEXT WEEK.
AVIATION
VALID THROUGH 19/00Z.
FEW-SCT CUMULUS CLOUDS AT 4K-8K FT THIS AFTERNOON AND EVENING,
SKC OTHERWISE. SFC WINDS NW/W AT 6-12 KTS, WITH THE STRONGEST
WINDS KTUS EASTWARD LATE THIS MORNING INTO THE EVENING. OTHERWISE
SFC WINDS WILL BE TERRAIN DRIVEN AND REMAIN UNDER 10 KTS. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
MINIMUM RH VALUES WILL BE IN THE 15-30 PERCENT
RANGE IN THE VALLEYS INTO NEXT WEEK. 20-FOOT WINDS MAINLY 15 MPH
OR LESS, WITH OCCASIONAL GUSTS TO 20-25 MPH. HIGH TEMPERATURES
WILL BE BELOW NORMAL THROUGH SATURDAY, WARMING TO NORMAL OR JUST
ABOVE NORMAL LEVELS SUNDAY INTO NEXT WEEK. THE NEXT CHANCE OF
PRECIPITATION WILL BE AROUND NEXT TUESDAY/WEDNESDAY WITH A SLIGHT
(~20%) CHANCE OF SHOWERS IN NORTHERN GRAHAM/GREENLEE AND SANTA
CRUZ COUNTIES.
TWC WATCHES/WARNINGS/ADVISORIES
NONE.
TETRAULT
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