138
FXUS65 KTWC 031036
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
336 AM MST SAT MAY 3 2025
SYNOPSIS
TEMPERATURES WILL REMAIN WARM AGAIN TODAY THEN COOL
TO WELL BELOW NORMAL SUNDAY INTO EARLY NEXT WEEK AS A STRONG
PACIFIC WEATHER SYSTEM IMPACTS THE DESERT SOUTHWEST. ALTHOUGH THIS
SYSTEM WILL BE DRY FOR THE MAJORITY OF SOUTHEAST ARIZONA...IT
WILL BRING STRONG AND GUSTY WINDS SUNDAY 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
THE UPPER PATTERN THIS MORNING IS DEFINED BY A
STRONG RIDGE OF HIGH PRESSURE ACROSS THE INTERMOUNTAIN WEST WITH
A WEAK, WEAKENING UPPER-LOW TRAPPED ACROSS SW ARIZONA. STILL
ANOTHER WARM DAY IN STORE FOR SOUTHEAST ARIZONA TODAY AS THERE IS
NOT MUCH COOL AIR ASSOCIATED WITH THIS FIRST SYSTEM. OVER THE PAST
12 HOURS, WE HAVE SEEN A WEAK BACKDOOR FRONT ENTER INTO THE
EASTERN PORTIONS OF THE CWA FROM NEW MEXICO. STRONG GUSTY
SOUTHEAST-TO-EAST WINDS LATE LAST EVENING HAVE SINCE TAPERED OFF
EARLY THIS MORNING, BUT THEY HAVE BEEN RESPONSIBLE FOR LINGERING
BLOWING DUST IN THE AIR THIS MORNING ACROSS EASTERN COCHSIE AND
GRAHAM COUNTY FROM ITS SOURCE IN NORTHWEST CHIHUAHUA MEXICO. IN
FACT, THE LATEST OBSERVATION AT 238 AM MST IN DOUGLAS (KDUG)
INDICATED 4 MILES VSBY IN HAZE/DUST. THIS BOUNDARY WILL CONTINUE
TO WEAKEN INTO THE AFTERNOON HOURS BUT THE COMBINATION OF THIS
SURFACE FEATURE ALONG WITH THE UPPER DIFFLUENCE AROUND THE WEAK
UPPER LOW SHOULD BE ABLE TO PRODUCE A FEW LIGHT SHOWERS THIS
AFTERNOON ACROSS GRAHAM AND GREENLEE COUNTIES WITH THE POTENTIAL
FOR A DRY LIGHTNING STRIKE ACROSS THE NORTHERN PORTIONS OF THE
AFOREMENTIONED COUNTIES.
STRONG SSE FLOW SEEN ON THE LATEST WV IMAGERY THIS MORNING OFF
THE WEST COAST (ALONG THE WESTERN PERIPHERY OF THE AMPLIFIED
RIDGE) WILL ALLOW FOR AN ANOMALOUSLY STRONG UPPER LOW TO DEVELOP
OVER SOUTHERN CALIFORNIA TONIGHT INTO SUNDAY MORNING. THE MAIN
IMPACT FROM THIS SYSTEM WILL BE FROM THE STRONG AND GUSTY
SOUTHWEST WINDS SUNDAY. SIMILAR TO THE THINKING 24-HOURS AGO, THE
STRONG SURFACE GRADIENT WILL DRIVE THE WINDY CONDITIONS SUNDAY,
WITH THE 50KT FLOW GENERALLY REMAINING ABOVE 500 MB ACROSS OUR
NECK OF THE WOODS THROUGHOUT THE EVENT. THIS WILL LIMIT THE HIGH-
END GUSTS EXPECTED, WITH THE STRONGEST WINDS ALONG THE INTERNATIONAL
AND ARIZONA/NEW MEXICO BORDERS S AND SE OF TUCSON TO THE 40-45
MPH RANGE.
DECENT MOISTURE PLUME SEEN THIS MORNING ON THE GOES PWAT IMAGERY
AHEAD OF THE DEVELOPING UPPER LOW SHOULD HOLD TOGETHER ENOUGH TO
IMPORT PWAT VALUES AROUND 0.75 INCHES INTO THE WESTERN PORTIONS
OF THE CWA OVERNIGHT TONIGHT. THE TRAJECTORY OF THE UPPER LOW IS
SLIGHTLY SOUTH OF ITS PREVIOUS RUNS WHICH SHOULD HELP IMPORT SOME
MOISTURE FARTHER EAST. ALTHOUGH THE EASTERN HALF OF THE CWA WILL
HOLD ONTO DEWPOINTS IN THE LOWER 20S SUNDAY RESULT IN MINIMUM
HUMIDITIES IN THE 12-17 PERCENT RANGE, THE WESTERN PORTIONS OF THE
FORECAST AREA WILL SEE MINIMUM HUMIDITIES IN THE 20-40 PERCENT
RANGE. I DECIDED TO TRIM OFF THE WESTERN PORTIONS OF THE INHERITED
FIRE WEATHER WATCH FOR SUNDAY, KEEPING ONLY FIRE WEATHER ZONE 152.
EVEN THROUGH THE WINDS WILL BE SOUTHWEST 20-30 MPH WITH GUSTS TO
45 MPH, IT IS THE RH VALUES THAT MAY LIMIT THE CRITICAL FIRE
WEATHER CONDITIONS. PER COORDINATION WITH EPZ, WE DECIDED TO PUNT
THE DECISION TO UPGRADE THE FIRE WEATHER WATCH TO THE DAYSHIFT
WITH ANOTHER RUN TO BUILD CONFIDENCE IN AREAL AND TEMPORAL EXTENT
OF THE RED FLAG CONDITIONS.
OTHERWISE, THE UPPER-LOW ISN'T TOO EXCITED TO DEPART THE REGION AS
IT MEANDERS TO THE FOUR CORNERS THROUGH WEDNESDAY AS THE UPPER
RIDGE UPSTREAM POSITIVELY TILTS INTO THE PACIFIC NORTHWEST. WE
WILL REMAIN ON THE SOUTHERN PERIPHERY OF THIS SYSTEM LIMITING THE
POTENTIAL FOR PRECIPITATION ACROSS SOUTHEAST ARIZONA TO THE
NORTHERN PORTIONS OF THE FORECAST AREA. IN ANY EVENT, PCPN WILL BE
LIGHT WITH MAYBE A QUARTER INCH OF PCPN NEAR THE WHITE MOUNTAINS.
EXPECT AFTERNOON TEMPERATURES TO REMAIN BELOW NORMAL THE FIRST
HALF OF NEXT WEEK, WITH A WARMUP THE SECOND HALF OF THE WEEK
EXPECTED AS THE UPPER TROUGH IS REPLACED WITH AN AMPLIFYING RIDGE
ACROSS THE DESERT SOUTHWEST. IN FACT, THE 03/10Z NBM
PROBABILITIES, THERE IS A 49% CHANCE THAT KTUS WILL MEET OR EXCEED
100 DEGREES NEXT SATURDAY. HMMPH. I GUESS IT IS MAY AFTER ALL..
AVIATION
VALID THROUGH 04/12Z.
SKC-SCT CLOUDS AT 10K-13K FT AGL ACROSS MOST OF SOUTHEAST ARIZONA
THRU THE FORECAST PERIOD, WITH AREAS NE OF KSAD SCT-BKN CLOUDS AT 6K-
10K FT AGL AND A SLIGHT CHANCE OF -SHRA/-TSRA. SFC WIND GENERALLY
LESS THAN 12 KTS THRU 03/18Z AND AGAIN AFT 04/03Z. SFC WIND BETWEEN
03/18Z AND 04/03Z, SLY/SWLY AT 10-15 KTS AND GUSTS TO 25 KTS EAST OF
A KOLS TO KSAD LINE, WITH WIND SPEEDS LESS THAN 12 KTS WEST OF THIS
LINE. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
ABOVE NORMAL TEMPERATURES AND MAINLY DRY
CONDITIONS TODAY. THERE WILL BE A SLIGHT CHANCE FOR LIGHT SHOWERS
AND/OR AN ISOLATED DRY LIGHTNING STRIKE OR TWO IN THE WHITE
MOUNTAINS THIS AFTERNOON. EXPECT SOUTH TO SOUTHWEST 20-FOOT WINDS OF
15-20 MPH WITH GUSTS TO 25-30 MPH EAST OF A NOGALES TO SAFFORD LINE,
WITH WIND SPEEDS LESS THAN 15 MPH WEST OF THIS LINE.
A STRONG PACIFIC STORM SYSTEM WILL THEN MOVE INTO THE REGION SUNDAY,
RESULTING IN WINDY CONDITIONS AND THE POTENTIAL FOR CRITICAL FIRE
WEATHER CONDITIONS IN FIRE WEATHER ZONE 152 ON SUNDAY. A FIRE
WEATHER WATCH REMAINS IN EFFECT FROM 10 AM TO 8 PM MST FOR FIRE
WEATHER ZONE 152. WHILE WIND SPEEDS WILL EXCEED CRITICAL THRESHOLDS
ACROSS MUCH OF SOUTHEAST ARIZONA ON SUNDAY, MIN RH VALUES ARE
EXPECTED TO BE ABOVE CRITICAL THRESHOLDS (15%) ACROSS ALL BUT FIRE
WEATHER ZONE 152.
BELOW NORMAL TEMPERATURES AND LESS WIND MONDAY AND TUESDAY, WITH A
SHARP WARMING TREND MID TO LATE NEXT WEEK. THERE WILL BE A SLIGHT
CHANCE TO A CHANCE OF PRECIPITATION IN THE WHITE MOUNTAINS MONDAY
THROUGH WEDNESDAY OF NEXT WEEK.
TWC WATCHES/WARNINGS/ADVISORIES
FIRE WEATHER WATCH FROM SUNDAY MORNING THROUGH SUNDAY EVENING
FOR AZZ152.
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