407
FXUS65 KTWC 152005
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
105 PM MST MON SEP 15 2025
SYNOPSIS
MOISTURE SLOWLY MOVES IN THIS WEEK LEADING TO
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS SOUTH AND EAST OF
TUCSON THROUGH THE MIDDLE OF THE WEEK. STORM COVERAGE INCREASES
LATER IN THE WEEK. TEMPERATURES WILL BE SLIGHTLY ABOVE NORMAL
THROUGH THE MIDDLE OF THE WEEK, THEN AROUND NORMAL LATE THIS WEEK.
DISCUSSION
CLOUDS ARE BUILDING UP AREAS TUCSON SOUTH AND
EASTWARD WITH ISOLATED TO SCATTERED STORMS AND SHOWERS FORMING ON
THE TERRAIN THEN GENERALLY MOVING NORTHEASTWARD. THE 18Z SOUNDING
LAUNCHED IN TUCSON OBSERVED 1.01 INCHES OF PWATS WITH NEARLY 1600
J/KG OF DCAPE. STORMS AND SHOWERS WILL CONTINUE TO DEVELOP INTO
THE AFTERNOON HOURS WITH THE MAIN CONCERN BEING MODERATE TO HEAVY
RAINFALL THAT MAY LEAD TO FLASH FLOODING AND STRONG, GUSTY OUTFLOW
WINDS THAT MAY KICK UP DUST.
HIGH PRESSURE IS CENTERED TO THE SOUTH OVER NORTHERN MEXICO WITH
A SMALL UPPER LEVEL LOW OFF THE COAST OF BAJA. THE PLACEMENT OF
THESE TWO FEATURES WILL ALLOW MOISTURE TO SLOWLY MOVE INTO
SOUTHEAST ARIZONA THROUGH THE WORK WEEK. STARTING TOMORROW, PWAT
INCREASES TO AROUND 1.25" OVER MOST OF THE CWA WHICH WILL LEAD TO
AN INCREASE IN STORM CHANCES AND COVERAGE. THIS IS BACKED UP BY
HREF MEMBERS WHICH SHOW SCATTERED THUNDERSTORM COVERAGE OVER MUCH
OF THE AREA EXCEPT FOR PINAL COUNTY. WITH THE ADDED MOISTURE
HEAVY RAINFALL WILL BE THE MAIN CONCERN WITH GUSTY TO STRONG
OUTFLOWS SECONDARY. MODELS SHOW A SLIGHT REDUCTION IN ACTIVITY
WEDNESDAY, BUT STILL EXPECT THERE TO BE ISOLATED THUNDERSTORMS
ESPECIALLY ALONG THE INTERNATIONAL BORDER. THE HIGH PRESSURE TO
THE SOUTH WILL INCREASE HEIGHTS OVER SOUTHERN ARIZONA LEADING TO
TEMPERATURES A FEW DEGREES ABOVE NORMAL TODAY AND TUESDAY.
THURSDAY INTO FRIDAY THE UPPER LOW OFF BAJA MOVES NORTHWARD
ALLOWING A LONG FETCH OF SOUTHERLY MID-LEVEL WINDS THAT ADVECT
TROPICAL MOISTURE INTO SOUTHERN CALIFORNIA AND SOUTHERN ARIZONA.
THIS BRINGS PWATS TO 25-75 PERCENT ABOVE NORMAL WITH THE MOST
ANOMALOUS MOISTURE WEST OF TUCSON. THIS WILL LEAD TO AN UPTICK IN
STORM ACTIVITY THURSDAY MAINLY FROM TUCSON SOUTH AND WESTWARD
THEN EXPAND TO ENCOMPASS ALL OF SOUTHEAST ARIZONA FRIDAY. STILL
SOME UNCERTAINTY WITH HOW FAR EAST THE LOW WILL END UP AS IT MOVES
NORTH. THE FURTHER EAST IT ENDS UP THEN THE FURTHER EAST THE
ANOMALOUS MOISTURE WILL BE, WHICH WOULD INCREASE POPS AND THE
HEAVY RAINFALL THREAT. THE ADDED MOISTURE WILL ALSO BRING
TEMPERATURES DOWN TO AROUND NORMAL WEDNESDAY INTO THE WEEKEND.
AVIATION
VALID THROUGH 17/00Z.
MOSTLY SKC CONDITIONS AREAS WEST OF KTUS. SOUTH AND EAST OF KTUS
INCLUDING KOLS, KDUG, AND KFHU CLOUDS ARE SCT TO OVC AOA 7 TO 10K
FT AGL WITH ISOLD TO SCT STORMS AND SHOWERS IN THE AREA. WITH STORMS
AND SHOWERS EXPECT LOCALLY HEAVY RAINFALL AND ERRATIC WINDS UP TO
40 KTS. CHANCES FOR STORMS AND SHOWERS WILL DIMINISH BY 16/03Z.
OTHER THAN THUNDERSTORM DRIVEN, SFC WINDS WILL BE FROM THE
NORTHWEST BECOMING LIGHT AND VARIABLE OVERNIGHT. CLOUD COVER WILL
LESSEN OVERNIGHT BECOMING SKC TO FEW AOA 10 TO 12K FT AGL BY
16/05Z. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
MINIMUM RH VALUES IN THE 15-30 PERCENT RANGE
THIS AFTERNOON, THEN 20-35 PERCENT THEREAFTER. ISOLATED
THUNDERSTORMS POSSIBLE TODAY TUCSON SOUTH AND EASTWARD WITH
GREATER COVERAGE AND CHANCES STARTING TUESDAY AFTERNOON. STORM
CHANCES DECREASE SOME WEDNESDAY THEN INCREASE THURSDAY AND FRIDAY
AS MORE MOISTURE MOVES IN. 20-FOOT WINDS WILL BE 8-12 MPH WITH
SOME AFTERNOON/EARLY EVENING GUSTS TO AROUND 20 MPH OVER THE NEXT
WEEK.
TWC WATCHES/WARNINGS/ADVISORIES
NONE.
MALARKEY
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