773
FXUS65 KTWC 042119
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
219 PM MST SUN MAY 4 2025
SYNOPSIS
A STRONG PACIFIC WEATHER SYSTEM WILL BRING COOLER TEMPERATURES
OVER THE COMING DAYS WITH PERIODIC CHANCES FOR ISOLATED SHOWERS
AND POTENTIALLY A THUNDERSTORM. WINDY CONDITIONS TODAY WILL GIVE
WAY TO LIGHTER WINDS WITH AFTERNOON BREEZES MONDAY AND TUESDAY. TEMPERATURES
WILL THEN REBOUND THE SECOND HALF OF NEXT WEEK, WITH THE
POSSIBILITY FOR THE CENTURY MARK RETURNING NEXT WEEKEND.
DISCUSSION
A DEEP, ANOMALOUS TROUGH WILL IMPACT THE REGION TODAY THROUGH THE
COMING SEVERAL DAYS. THIS AFTERNOON THE TROUGH AXIS SITS OVER
SOUTHERN CALIFORNIA AND NORTHERN BAJA AND WILL CROSS INTO SOUTHERN
ARIZONA AND NORTHERN SONORA THROUGH TONIGHT. A POTENT VORTICITY
MAX IS EVIDENT ON WATER VAPOR IMAGERY ROUNDING THE BASE OF THE
TROUGH THIS AFTERNOON, WHICH WILL BE THE IMPETUS FOR TODAY'S
WINDS AND CHANCES FOR SHOWERS AND THUNDERSTORMS. A SWATH OF
RELATIVELY HIGHER MOISTURE LIES OVER WESTERN PIMA COUNTY THIS
AFTERNOON, MEASURED AT 0.6-0.7 INCHES OF PRECIPITABLE WATER BY
GOES-WEST AND SURFACE DEW POINTS IN THE 40S. THIS WILL PROVIDE
ADEQUATE MOISTURE FOR THUNDERSTORMS WITH MODERATE TO POTENTIALLY
HEAVY RAINFALL RATES TO MOVE THROUGH THE FAR WESTERN PORTIONS OF
THE COUNTY (INCLUDING AJO) THIS AFTERNOON AND EVENING. FURTHER
EAST, MOISTURE QUALITY DROPS OFF BUT REMAINS ENOUGH FOR
CONVECTIVE ACTIVITY NEAR, NORTH, AND EAST OF TUCSON. DRY LIGHTNING
THIS AFTERNOON BECOMES A CONCERN WITH THE REDUCED MOISTURE IN THE
ATMOSPHERE, ESPECIALLY IN GRAHAM AND GREENLEE COUNTIES. GUSTY
SOUTH TO SOUTHWEST WINDS WILL CONTINUE THROUGH THE AFTERNOON AND
TAPER OFF THIS EVENING ACROSS MOST OF SOUTHEASTERN ARIZONA. WINDS
OF 20-30 MPH AND GUSTS TO 45 MPH ARE LIKELY IN SOUTHERN AREAS
CLOSER TO THE INTERNATIONAL BORDER, WITH 15-25 MPH WINDS AND GUSTS
TO 35 MPH ELSEWHERE. SOME POCKETS OF BLOWING DUST MAY IMPACT
TRAVEL WITH THESE WINDS, THOUGH CONFIDENCE IN ANY LOCATION OR
SEVERITY IS LOW.
THE UPPER LEVEL LOW IS EXPECTED TO LINGER OVER THE REGION THROUGH
EARLY THIS WORK WEEK, WITH THE CENTER OF IT OVER SOUTHERN TO
CENTRAL ARIZONA ON MONDAY. THROUGH MONDAY MORNING AN ASSOCIATED
LOW LEVEL FRONT WILL BE PUSHING THROUGH SOUTHEASTERN ARIZONA,
WHICH CURRENTLY SITS OVER FAR WESTERN ARIZONA AND SOUTHERN
CALIFORNIA. THIS FRONT SHOULD PUSH CONVECTION THAT FORMS THIS
AFTERNOON OVER WESTERN PIMA COUNTY EASTWARD OVERNIGHT, HOWEVER THE
CONVECTIVE ACTIVITY'S LONGEVITY IS UNCERTAIN. MODEL TO MODEL AND
RUN TO RUN CONSISTENCY HAS BEEN LACKING, BUT IT'S A STRONG ENOUGH
FORCING MECHANISM TO BRING AT LEAST SLIGHT (15-25 PERCENT) CHANCES
OF SHOWERS INTO THE TUCSON AREA MONDAY MORNING, WITH HIGHER
CHANCES NORTHWARD THROUGH PINAL COUNTY. THEN MONDAY AFTERNOON,
COLD TEMPERATURES ALOFT WILL ALLOW FOR SHALLOW DIURNAL CONVECTION,
AIDED BY BROAD CYCLONIC FLOW. THIS SHOULD PRODUCE ISOLATED TO
SCATTERED SHOWERS ACROSS MUCH OF SOUTHEASTERN ARIZONA THROUGH THE
EVENING, WITH GREATER CHANCES AGAIN NORTHWARD THROUGH PINAL AND
NORTHERN GRAHAM AND GREENLEE COUNTIES. THE AFOREMENTIONED MOISTURE
PLUME (OVER WESTERN PIMA THIS AFTERNOON), WILL HAVE SHIFTED
NORTHEAST BY THIS TIME, WHICH MAY CONTRIBUTE TO PERIODS OF
MODERATE PRECIPITATION RATES IN PINAL COUNTY IF SHOWERS DEVELOP
THERE ON MONDAY AS RECENT HIGH- RESOLUTION MODEL RUNS INDICATE.
THROUGH THIS PERIOD LIGHT SNOW WILL ALSO BE POSSIBLE ATOP MT
LEMMON, MT GRAHAM, AND THE WHITE MOUNTAINS, WITH SEVERAL INCHES OF
ACCUMULATION FORECAST OVER THE HIGHEST ELEVATIONS OF THE WHITE
MOUNTAINS.
BY TUESDAY, THE UPPER LOW WILL HAVE MOVED EAST INTO COLORADO AND
NEW MEXICO. ON THE BACK SIDE OF THIS EXITING SYSTEM ADDITIONAL
SHORTWAVES CROSS THE REGION, BRINGING ADDITIONAL CHANCES FOR
SHOWERS, ESPECIALLY OVER GRAHAM AND GREENLEE COUNTIES. A FINAL
WAVE ASSOCIATED WITH THE EXITING LOW WILL LIKELY CROSS TO THE
NORTHEAST WEDNESDAY, PRODUCING ANOTHER CHANCE OF SHOWERS TO GRAHAM
AND GREENLEE COUNTIES. THESE FOLLOWING CHANCES AFTER MONDAY WILL
FEATURE A DECREASE IN AVAILABLE MOISTURE AS WELL AS LESS FOCUSED
SYNOPTIC FORCING, KEEPING FORECAST PRECIPITATION AMOUNTS LIGHT.
DURING THIS PERIOD MONDAY THROUGH WEDNESDAY BELOW NORMAL
TEMPERATURES ARE LIKELY BEFORE QUICKLY WARMING BACK UP MID-WEEK
ONWARDS. A RIDGE IS FORECAST TO BUILD ACROSS THE WESTERN CONUS BY
THE END OF THE WEEK, BRINGING FORECAST TEMPERATURES ACROSS
SOUTHEASTERN ARIZONA INTO THE 90 TO 100 DEGREE RANGE FRIDAY
THROUGH THE WEEKEND.
AVIATION
VALID THROUGH 06/00Z.
FEW-SCT CUMULUS AT 7K-10K FEET SOUTH AND WEST OF KTUS, SCT-BKN
NORTH AND EAST OF KTUS THROUGH THIS EVENING. ISOLATED TO SCATTERED
LIGHT SHOWERS AND ISOLATED THUNDERSTORMS GENERALLY NORTH AND EAST
OF KTUS THROUGH THIS EVENING AS WELL. GUSTY WINDS OF 20-30 KTS
AND GUSTS TO 42 KTS DECREASES AFTER 05/02Z, WITH SURFACE WINDS
8-14 KTS OVERNIGHT. FEW-SCT 4K-7K CEILINGS MOVE IN AFTER 05/09Z.
ISOLATED TO SCATTERED SHOWERS AGAIN ON MONDAY, WITH LOW ENOUGH
COVERAGE TO KEEP OUT OF ANY ONE TAF FOR NOW. LIGHTER WINDS MONDAY
BUT STILL BREEZY IN THE AFTERNOON AT 10-17 KTS AND GUSTS TO 26
KTS. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
A RED FLAG WARNING REMAINS IN EFFECT FOR ELEVATIONS BELOW 5000
FEET IN GRAHAM AND COCHISE COUNTIES. GUSTY WINDS WILL CONTINUE
THROUGH THE EARLY EVENING WHILE OBSERVED RELATIVE HUMIDITIES ARE
DOWN TO AROUND 12-16 PERCENT. LIGHT SHOWERS ARE MOVING THROUGH
GRAHAM INTO GREENLEE COUNTIES WHICH MAY BRING THE ISOLATED THREAT
OF DRY LIGHTNING THIS AFTERNOON AND EARLY EVENING.
WINDS WILL DIMINISH THIS EVENING BUT REMAIN BREEZY OUT OF THE
SOUTHWEST. 15-20 MPH WINDS WITH GUSTS TO 35 MPH WILL CONTINUE
THROUGH MUCH OF THE EVENING, THEN WILL BECOME LIGHT AND UNDER 12
MPH BY AROUND MIDNIGHT. LIGHTER WINDS ARE EXPECTED MONDAY BUT WILL
BE BREEZY AT 10-20 MPH AND GUSTS 20-30 MPH OUT OF THE SOUTHWEST.
WINDS ON THE HIGHER SIDE OF THAT SPECTRUM ARE EXPECTED IN SOUTHERN
AND EASTERN AREAS, ESPECIALLY TOWARDS THE SOUTHEAST OF COCHISE
COUNTY. COOLER TEMPERATURES AND MOISTURE MOVING INTO THE AREA WILL
BRING MINIMUM RELATIVE HUMIDITIES UP, THOUGH LINGERING DRY AIR
WILL REMAIN IN CENTRAL TO EASTERN COCHISE AND GRAHAM COUNTIES WITH
MINIMUM VALUES DOWN TO AROUND 18 PERCENT. ISOLATED TO SCATTERED
SHOWERS WILL BE POSSIBLE AS THE ONGOING SYSTEM MOVES THROUGH.
MINIMUM RELATIVE HUMIDITY REMAINS ABOVE 20 PERCENT WITH
UNSEASONABLY COOL TEMPERATURES ON TUESDAY, THEN A WARMING AND
DRYING TREND IS EXPECTED FOR THE SECOND HALF OF THE WEEK.
TWC WATCHES/WARNINGS/ADVISORIES
RED FLAG WARNING UNTIL 8 PM MST THIS EVENING FOR AZZ152.
PUBLIC...EDWARDS
AVIATION...EDWARDS
FIRE WEATHER....EDWARDS
VISIT US ON FACEBOOK...TWITTER...YOUTUBE...AND AT WEATHER.GOV/TUCSON
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