454
FXUS65 KTWC 040900
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
200 AM MST SUN MAY 4 2025
SYNOPSIS
TEMPERATURES WILL COOL TO BELOW NORMAL THE NEXT FEW
DAYS AS A STRONG PACIFIC WEATHER SYSTEM IMPACTS THE DESERT
SOUTHWEST. THIS SYSTEM WILL BRING STRONG AND GUSTY WINDS TODAY
RESULTING IN THE POTENTIAL FOR CRITICAL FIRE WEATHER CONDITIONS
EAST OF TUCSON. TEMPERATURES WILL THEN REBOUND THE SECOND HALF
OF NEXT WEEK, WITH THE POSSIBILITY FOR THE CENTURY MARK RETURNING
NEXT WEEKEND.
DISCUSSION
WE ARE TRANSITIONING INTO AN MILDLY-ACTIVE PATTERN
FOR SOUTHEAST ARIZONA THE NEXT FEW DAYS AS A STRONG PACIFIC STORM
SYSTEM DEVELOPING OVER SOUTHERN CALIFORNIA THIS MORNING MOVES INTO
OUR NECK OF THE WOODS. THE LATEST WATER VAPOR SATELLITE IMAGERY
INDICATED STRONG FLOW ALONG THE BACKSIDE OF THIS FEATURE ALLOWING
THE UPPER LOW TO STRENGTHEN AND THE MEAN TROUGH TO AMPLIFY AS IT
SLOWLY MAKES ITS WAY INTO SOUTHWEST ARIZONA LATER THIS MORNING.
GOES PWAT WATER INDICATES A DECENT PLUME OF MOISTURE (0.75-0.85
INCHES) GETTING WRAPPED UP AHEAD OF THIS FEATURE, EXTENDING FROM
THE BAJA SPUR INTO FAR SW AZ. DUE TO THE HIGHER AMPLITUDE OF THE
THE TROUGH COMPARED TO PREVIOUS NUMERICAL MODEL RUNS, MOISTURE IS
SLIGHTLY DEEPER THAN PREVIOUSLY THOUGHT, INCREASING THE LIKELIHOOD
THAT SOUTHEAST ARIZONA WILL SEE MEASURABLE PRECIPITATION. STRONG
SSW FLOW AT THE SURFACE WILL IMPORT LOW-LEVEL MOISTURE FROM THE
NORTHERN GULF OF CALIFORNIA INTO WESTERN PIMA COUNTY AROUND
DAYBREAK THIS MORNING. AS THE FLOW SHIFTS TO A MORE SWLY DIRECTION
TODAY 20 TO 30 MPH WITH GUSTS TO 40-45 MPH, WE WILL SEE THE LOW-
LEVEL MOISTURE CREEP EAST ACROSS OUR CWA THROUGH THE DAY BUT THERE
SHOULD STILL BE A STRONG GRADIENT BETWEEN SURFACE DEWPOINTS IN
THE LOWER 50S OUT WEST TO THE MID 20S ALONG THE ARIZONA/NEW MEXICO
STATELINE. THE RED FLAG WARNING THAT WE HAVE UP TODAY ACROSS FIRE
WEATHER ZONE 152 (EASTERN COCHISE, SOUTHERN GRAHAM AND SOUTHERN
GREENLEE COUNTIES) IS FRAUGHT WITH PERIL AS RH CONDITIONS WILL
MAKE CRITICAL CONDITIONS BORDERLINE. MY OWN EXPERIENCE SUGGESTS
THAT IN THIS TYPE OF SCENARIO, DRY-AIR OUT ACROSS THE EASTERN
ZONES IS HESITANT TO MOVE OUT OF THE AREA. GIVEN THIS, I HAVE
DECIDED TO HOLD ONTO THE RED FLAG WARNING BUT CRITICAL FIRE
WEATHER CONDITIONS MAY BE MORE LOCALIZED AND BRIEF THAN WIDESPREAD
TODAY.
PRECIPITATION REALLY BEGINS TO IMPACT OUR AREA THIS AFTERNOON INTO
THIS EVENING AS THE SURFACE FRONTAL BOUNDARY MOVING INTO THE
WESTERN PORTIONS INTERACTS WITH THE LOWER LEVEL MOISTURE AND THE
DIFFLUENT FIELD ALOFT WORKS WITH THE MID-LEVEL MOISTURE FROM
TUCSON NORTHEAST. THE 04/00Z HREF 3-HR QPF PROBABILITY MATCHED
MEAN INDICATES A 10 PERCENT CHANCE OF GREATER THAN AN INCH OF
RAINFALL ACROSS WESTERN PIMA COUNTY BETWEEN 04/21Z AND 05/06Z
WHERE THE DEEPER LOW-LEVEL MOISTURE RESIDES. RAINFALL AMOUNTS
THROUGH 12Z MONDAY SHOULD BE 0.25-0.50 INCHES ACROSS WESTERN PIMA
COUNTY, TO 0.10 TO 0.50 NEAR THE HIGHER TERRAIN FROM TUCSON
NORTHEAST INTO GRAHAM AND GREENLEE COUNTIES. THE HIGHEST ELEVATIONS
WILL SEE 1-4 INCHES OF SNOWFALL WITH THIS SYSTEM. EXPECT POPS TO
DECREASE LATE TONIGHT INTO MONDAY MORNING, INCREASING AGAIN
MONDAY AFTERNOON AND EVENING AS A SECONDARY VORT-LOBE ROTATES
AROUND THE MEAN UPPER-LOW.
THE UPPER-LOW ISN'T TOO EXCITED TO DEPART THE REGION AS THE UPPER
RIDGE UPSTREAM POSITIVELY TILTS INTO THE PACIFIC NORTHWEST
MAINTAINING A BAGGY TROUGH ACROSS ARIZONA. THIS SHOULD RESULT IN
A CHANCE OF PCPN ACROSS THE NORTHEAST PORTIONS OF OUR FORECAST
AREA THROUGH WEDNESDAY. OTHERWISE, EXPECT AFTERNOON TEMPERATURES
TO REMAIN BELOW NORMAL THE FIRST HALF OF THE WEEK, WITH A WARMUP
THE SECOND HALF OF THE WEEK AS THE UPPER TROUGH IS REPLACED WITH
AN AMPLIFYING RIDGE ACROSS THE DESERT SOUTHWEST. THE 03/05Z NBM
INDICATES A 65% CHANCE THAT KTUS WILL MEET OR EXCEED 100 DEGREES
NEXT SATURDAY.
AVIATION
VALID THROUGH 05/12Z.
FEW-SCT CLOUDS AT 6K-8K FT AGL BECOMING SCT-BKN CLOUDS AFT 04/18Z
THRU THE END OF THE FORECAST PERIOD, WITH A SLIGHT CHANCE TO CHANCE
OF -SHRA/-TSRA. SFC WIND INCREASING AFT 04/15Z, WITH SLY/SWLY SFC
WIND AT 13-18 KTS THRU 04/18Z AND THEN 20-26 KTS AND GUSTS TO 35-40
KTS BETWEEN 04/18Z AND 05/02Z. DECREASING SFC WIND AFT 05/02Z, WITH
SFC WIND AT 8-14 KTS BY 05/06Z. AVIATION DISCUSSION NOT UPDATED FOR
TAF AMENDMENTS.
FIRE WEATHER
A STRONG PACIFIC STORM SYSTEM WILL RESULT IN WINDY
CONDITIONS TODAY, ALONG WITH CRITICAL FIRE WEATHER CONDITIONS IN
FIRE WEATHER ZONE 152. A RED FLAG WARNING REMAINS IN EFFECT FROM 10
AM TO 8 PM MST TODAY FOR FIRE WEATHER ZONE 152. WHILE WIND SPEEDS
WILL EXCEED CRITICAL THRESHOLDS ACROSS MUCH OF SOUTHEAST ARIZONA
TODAY, MIN RH VALUES ARE EXPECTED TO BE ABOVE CRITICAL THRESHOLDS
(15%) ACROSS ALL BUT FIRE WEATHER ZONE 152.
COOLER TEMPERATURES AND BELOW NORMAL HIGHS THROUGH TUESDAY, ALONG
WITH A SLIGHT CHANCE TO CHANCE OF SHOWERS AND THE POTENTIAL FOR A
FEW THUNDERSTORMS. EXPECT SOUTH TO SOUTHWEST 20-FOOT WINDS OF 20-30
MPH AND GUSTS TO AROUND 45 MPH TODAY. LESS WIND ON MONDAY, BUT
BREEZY CONDITIONS STILL PERSIST ACROSS COCHISE, GRAHAM AND GREENLEE
COUNTIES. HIGHER RH VALUES TONIGHT INTO TUESDAY. A SHARP WARMING
TREND RETURNS MID TO LATE THIS WEEK.
TWC WATCHES/WARNINGS/ADVISORIES
RED FLAG WARNING FROM 10 AM THIS MORNING TO 8 PM MST THIS EVENING
FOR AZZ152.
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