448
FXUS65 KPSR 181811
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1111 AM MST WED MAR 18 2026
UPDATE
UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- A HISTORIC MARCH HEATWAVE THROUGH THIS WEEKEND WILL PRODUCE
RECORD SHATTERING LOWER DESERT HIGH TEMPERATURES EXCEEDING 100
DEGREES AS EARLY AS TODAY.
- AN EXTREME HEAT WARNING WILL TAKE EFFECT TODAY ACROSS
SOUTHEAST CALIFORNIA AND THURSDAY ACROSS ARIZONA DESERTS, AND
CONTINUING THROUGH THIS SUNDAY.
- THE UNPRECEDENTED AFTERNOON HEAT WILL BE DANGEROUS, ESPECIALLY
WITH ANY STRENUOUS OR LONG-DURATION OUTDOOR ACTIVITIES WITHOUT
PROPER HYDRATION AND TAKING BREAKS IN THE SHADE, OR AIR
CONDITIONING.
SHORT TERM /TODAY THROUGH THURSDAY/
THE HOTTEST TEMPERATURES THE SOUTHWESTERN U.S. HAS EVER
EXPERIENCED IN MARCH WILL ARRIVE BY THURSDAY AS A RECORD STRENGTH
HIGH PRESSURE CENTER SLOWLY SHIFTS FROM SOUTHERN CALIFORNIA INTO
ARIZONA ON THURSDAY. H5 HEIGHTS ARE FORECAST TO CONTINUE TO RISE
TODAY BEFORE PEAKING AT AROUND 596-597DM ON THURSDAY. RECORD H5
HEIGHTS FOR THE MONTH OF MARCH FOR THE DESERT SOUTHWEST ARE
BETWEEN 591-593DM, MEANING THIS RIDGE WILL SMASH THE ALL-TIME
MARCH RECORD. THIS HIGH PRESSURE SYSTEM IS SOMETHING LIKE WE WOULD
TYPICALLY GET DURING SUMMERTIME HEAT EVENTS. CLIMATOLOGICAL
RECORD HIGH H5 AND H7 TEMPERATURES HAVE ALREADY SPREAD ACROSS ALL
OF CALIFORNIA AND THE BULK OF THE DESERT SOUTHWEST WITH H8
TEMPERATURES SURPASSING RECORDS ACROSS OUR AREA BY LATER TODAY.
FULL MIXING OF THE RECORD HEAT ALOFT INTO THE BOUNDARY LAYER WILL
TAKE ANOTHER DAY OR SO, KEEPING SURFACE TEMPERATURES FROM REACHING
THEIR PEAK UNTIL FRIDAY.
THE HEAT OVER THE NEXT SEVERAL DAYS WILL BE UNPRECEDENTED FOR
THIS TIME OF YEAR, BUT CONSIDERING HOW MUCH ABOVE CLIMATOLOGICAL
RECORDS THIS RIDGE WILL BE, THERE ARE A COUPLE OF POSITIVE THINGS.
THE DAYLENGTH IS STILL AT LEAST TWO HOURS SHY OF WHAT WE GET FROM
LATE MAY-JULY AND THE DRY AIR WILL HELP WITH OVERNIGHT
TEMPERATURES. A WIDE DIURNAL TEMPERATURE RANGE WILL ALLOW FOR SOME
RELIEF FROM THE HEAT DURING THE OVERNIGHT HOURS WITH LOW
TEMPERATURES MOSTLY STAYING IN THE 60S, HOWEVER STILL NEAR 15
DEGREES ABOVE NORMAL. DAYTIME HIGHS TODAY ARE EXPECTED TO CLIMB TO
BETWEEN 100-104 DEGREES ACROSS SOUTHEAST CALIFORNIA AND SOUTHWEST
ARIZONA TO AROUND 100 DEGREES IN THE PHOENIX AREA. AS THE CENTER
OF THE RIDGE MOVES OVERHEAD ON THURSDAY, HIGHS WILL EASILY BREACH
100 DEGREES IN THE PHOENIX AREA TO AS HIGH AS 103-106 DEGREES OVER
THE WESTERN LOWER DESERTS OF SE CA AND SW AZ.
AS STATED YESTERDAY, REACHING 100 DEGREES IN MARCH IS HIGHLY
UNCOMMON, WITH THE AVERAGE FIRST 100 DEGREE DAYS BEING IN LATE-
APRIL TO START OF MAY. SO, OVER A MONTH EARLY AND THE PHOENIX
CLIMATE SITE WILL SET A NEW RECORD EARLIEST 100 DEGREE, WITH THE
CURRENT EARLIEST SITTING AT MARCH 26TH. IT GOES WITHOUT SAYING,
THIS WILL BE AN IMPACTFUL HEATWAVE. EXTREME HEAT WARNINGS BEGIN
TODAY ACROSS SOUTHEAST CALIFORNIA AND THE REST OF THE AREA
STARTING THURSDAY.
LONG TERM /FRIDAY THROUGH TUESDAY/
THE HOTTEST DAYS THIS WEEK STILL LOOK TO BE ON FRIDAY AND SATURDAY
WITH HIGHS MOSTLY BETWEEN 103-107 DEGREES, ROUGHLY 25 DEGREES
ABOVE NORMAL AND 7-10 DEGREES ABOVE DAILY RECORDS. GUIDANCE HAS
BARELY DEVIATED OVER THE PAST COUPLE OF DAYS WITH THE RIDGE
STARTING TO WEAKEN EVER SO SLOWLY STARTING FRIDAY AND MORE SO
SATURDAY INTO SUNDAY. H5 HEIGHTS ARE FORECAST TO DROP BACK TO
BETWEEN 585-588DM BY LATER SATURDAY BEFORE SETTLING INTO A
582-585DM RANGE STARTING SUNDAY, STILL WELL ABOVE THE 90TH
PERCENTILE OF CLIMATOLOGY. THE WEAKER RIDGE SHOULD ALLOW FOR
DAYTIME HIGHS TO DROP TO BETWEEN 99-102 DEGREES BY SUNDAY.
ONE NOTICEABLE CHANGE WITH THE GUIDANCE IS A HIGHER LIKELIHOOD OF
HOLDING ONTO HIGHER HEIGHTS WELL INTO OR EVEN THROUGH THE MAJORITY
OF NEXT WEEK. ENSEMBLE MEAN H5 HEIGHTS ARE NOW SHOWN TO STAY
CLOSER TO THE 97TH PERCENTILE OF CLIMATOLOGY INTO AT LEAST THE
MIDDLE OF NEXT WEEK AND NEARLY CERTAIN TO STAY ABOVE THE 90TH
PERCENTILE. THIS MEANS THE HEAT WILL NOT GO AWAY NEXT WEEK AND
TEMPERATURES ARE LIKELY TO STAY AT OR JUST ABOVE DAILY RECORDS
THROUGH AT LEAST THE FIRST HALF OF NEXT WEEK. NBM FORECAST HIGHS
HAVE RISEN BY SEVERAL DEGREES DURING THE MIDDLE PART OF NEXT WEEK
WITH LOWER DESERT READINGS STAYING MOSTLY IN THE UPPER 90S, OR
15-20 DEGREES ABOVE NORMAL.
AVIATION
UPDATED AT 1800Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT; AND
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO MAJOR AVIATION WEATHER CONCERNS WILL EXIST THROUGH THE TAF
PERIOD UNDER MOSTLY CLEAR SKIES. WINDS WILL GENERALLY FOLLOW
DIURNAL TENDENCIES, WITH SPEEDS UNDER 10 KTS AND PERIODS OF
VARIABILITY, PARTICULARLY PRECEDING DIRECTION SHIFTS. LATER IN THE
AFTERNOON, OCCASIONAL WESTERLY GUSTS INTO THE TEENS MAY DEVELOP
ACROSS THE PHOENIX AREA TERMINALS.
FIRE WEATHER
A HISTORIC HIGH PRESSURE WILL LEAD TO RECORD TEMPERATURES, VERY
DRY CONDITIONS, SEASONAL WINDS, AND MOSTLY SUNNY SKIES THROUGH THE
REST OF THE WEEK. HIGH TEMPERATURES WILL WARM TO AROUND 25
DEGREES ABOVE NORMAL FOR THURSDAY-SATURDAY BEFORE GRADUALLY
DROPPING OFF SUNDAY AND THROUGH EARLY NEXT WEEK. ABNORMALLY HOT
AND VERY DRY CONDITIONS WILL TRANSLATE TO MINRH READINGS OF 5-10%
TODAY THROUGH THIS WEEKEND. OVERNIGHT RECOVERIES WILL NOT BE
GREAT, WITH VALUES DROPPING TO 15-35% THROUGH THE REMAINDER OF
THE WEEK.
CLIMATE
DAILY RECORD HIGHS THROUGH EARLY NEXT WEEK:
DATE PHOENIX YUMA EL CENTRO
---- ------- ---- ---------
3/18 95 IN 2017 96 IN 2017 95 IN 2007
3/19 96 IN 2017 98 IN 2017 96 IN 2017
3/20 96 IN 2017 99 IN 2004 98 IN 2004
3/21 97 IN 2004 102 IN 2004 100 IN 2004
3/22 94 IN 1990 98 IN 2004 96 IN 2004
3/23 93 IN 1990 96 IN 1990 93 IN 1990
3/24 96 IN 2025 97 IN 2025 96 IN 2025
PSR WATCHES/WARNINGS/ADVISORIES
AZ...EXTREME HEAT WARNING UNTIL 8 PM MST SUNDAY FOR AZZ530.
EXTREME HEAT WARNING FROM 11 AM THURSDAY TO 8 PM MST SUNDAY FOR
AZZ531>555-559-561.
CA...EXTREME HEAT WARNING UNTIL 8 PM PDT SUNDAY FOR CAZ561>570.
SHORT TERM...KUHLMAN
LONG TERM...KUHLMAN
AVIATION...WHITTOCK/BERISLAVICH
FIRE WEATHER...BENEDICT/KUHLMAN
CLIMATE...18/KUHLMAN
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