698
FXUS65 KPSR 130505
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1005 PM MST Thu Mar 12 2026

.UPDATE...06Z Aviation Discussion.

&&

.KEY MESSAGES...

- Strong high pressure has quickly built over the region today
  leading to drying conditions and rapid warming with near record
  temperatures starting Friday.

- An even stronger high pressure system will build over the region
  next week, likely pushing daily highs into the triple digits
  across the lower deserts while breaking daily and monthly high
  temperature records.

- Widespread Minor Heat Risk is expected through the weekend
  before increasing to Moderate HeatRisk next week.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...
High pressure is quickly building over our region today, with H5
heights ranging from 586-588dm across the CWA. The northerly flow,
associated with the high pressure, has allowed for drier air to
move into our region. PWATs have gone from 0.5" yesterday down to
0.2" today. Additionally the rapidly strengthening high pressure
system has allowed for rapid warming. Temperatures early this
afternoon range from mid 80s to low 90s across the lower deserts,
which is around 10-13 degrees warmer than they were 24 hours ago.
Temperatures are expected to climb even higher today, topping out
in the low to mid 90s across the lower deserts and in the upper
70s to mid 80s across the higher terrain. The high will max out
tonight prior to weakening slightly and shifting southward
tomorrow. Despite this afternoon high temperatures tomorrow are
still forecasted to top out in the mid 90s across the lower
deserts and in the 80s across the higher terrain. Even with highs
in the mid 90s tomorrow daily records may be tied or even broken.

&&

.LONG TERM /SATURDAY THROUGH NEXT WEEK/...
An unprecedented heat wave for mid March is expected next week
across the Western U.S. with widespread temperature anomalies of
20-30F. Model guidance continues to show remarkable agreement
through all of next week with model trends over the past couple of
days suggesting an even stronger record breaking ridge settling
over the Western U.S. by Monday and lasting into late week. This
event is likely to break daily records by as much as 10 degrees
for many areas and all time March temperature records, especially
across the Southwestern U.S. where the largest positive height
anomalies are anticipated.

After this first high pressure system shifts southward by this
weekend, a weak shortwave trough will move across the Desert
Southwest on Saturday, but it will only stabilize temperatures.
Highs this weekend will still reach into the 90s with some spots
across southeast California and southwest Arizona reaching 95
degrees. By late Saturday, the next high pressure ridge will be
developing well off the coast of California, quickly reaching
record strength for this time of year on Sunday. Large negative
height anomalies developing across the Eastern U.S. will also
help drive an increasing amplitudinal pattern quickly expanding
the ridge over the Western U.S. by Monday.

Climatological record H2 heights are projected over the entire
West Coast and into the Western U.S. by early next week before
slowly shifting eastward throughout the rest of next week. A
large area of record H5 heights focused across the Southwestern
U.S. is also expected to develop by mid week and last through at
least next Thursday or Friday. Ensemble mean H5 heights of
588-592dm are shown across the Desert Southwest by Tuesday before
peaking as high as 595dm on or around next Thursday. For
reference, sounding climatology data for Las Vegas, Flagstaff, and
Tucson all show record H5 heights for March are around 590dm and
April 591dm, 593dm, and 592dm respectively. So, to put this in
better prospective the ridge for next week is forecast to be as
strong if not a little bit stronger than any ridge this region has
ever seen in March or April. Guidance does start to show some
weakening of the ridge by next weekend, but that is where model
uncertainty increases with some members hanging onto the ridge a
bit longer.

Record temperatures are forecast for the majority of next week,
particularly from Tuesday-Saturday. As the ridge begins to
move into the region on Monday, highs should warm into the mid 90s
for Phoenix to as warm as the upper 90s across the western
deserts. The first 100 degree temperatures are likely to be seen
by Tuesday with NBM forecast highs of 99-103 degrees across much
of southeast California and southwest Arizona. Phoenix may also
hit 100 degrees on Tuesday which would easily break the earliest
100 degree day on record (currently March 26, 1988). Tuesday
should also be our first day of fairly widespread Moderate
HeatRisk.

The center of the ridge is expected to move into our region by
Wednesday and slowly drift eastward through our region on at least
Thursday and likely even next Friday. Guidance shows the ridge
reaching its peak strength of 592-594dm around next Thursday,
becoming the strongest ridge ever for our region in March and
possibly stronger than any experienced during the month of April.
Forecast H8, H7, and H5 temperatures are all essentially at record
levels for Tuesday through at least next Friday. It is not a
question of whether we will get record temperatures next week, the
question should be by how much will they be broken. Highs are
nearly certain to top 100 degrees each day during the latter half
of next week with the hottest readings likely even topping 105
degrees at some point next Thursday-Saturday. NBM 75th percentile
temperatures continue to show potential for some spots to even
hit 110 degrees late next week. The earliest ever 105 degree day
in Phoenix is April 20th and the earliest 106 degree day is May 2.

Widespread Moderate HeatRisk will affect the area during the
latter half of next week with at least some potential for
localized areas of Major HeatRisk developing across the lower
deserts. However, the large diurnal swings may keep this from
occurring. Forecast lows are still shown to dip into the 60s for
the majority of the area during the entire event which only puts
the lows in the Minor category, affecting the calculation of the
overall HeatRisk. Either way, this event should easily bring high-
end Moderate HeatRisk for several days.

&&

.AVIATION...Updated at 0505Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT;
Southeast California/Southwest Arizona including KIPL and KBLH: :

No aviation concerns are expected during the TAF period. Winds
will once again follow diurnal trends with window of VRB to calm
conditions during the overnight and in between directional shifts.
Clear skies will give way to increasing high clouds Friday
afternoon and evening.

&&

.FIRE WEATHER...
High pressure will dominate across the region through next week
as temperatures warm to 10-15 degrees above normal starting today
before heating up even further(20-30 above normal) next week.
Much drier air has also settled into the region today with MinRHs
dropping to around or just below 10% and persisting through next
week. Overnight recoveries will be poor to fair, dropping to
between 25-40%. Winds will remain fairly light, but with periodic
afternoon gusts at around 20 mph, especially over the weekend into
early next week. As temperatures rise next week and humidities
stay unseasonably low, elevated fire danger is likely to become a
problem.

&&

CLIMATE...

Daily record highs later this week/early next week:

Date      Phoenix         Yuma         El Centro
----      -------         ----         ---------
3/12     94 in 1900    100 in 1916     95 in 2017
3/13     92 in 2017     95 in 2017     95 in 2017
3/14     95 in 2013     96 in 2017     97 in 2017
3/15     92 in 2013     98 in 1934    100 in 1934
3/16     99 in 2007     99 in 2007    100 in 2007
3/17     99 in 2007    101 in 2007    101 in 2007
3/18     95 in 2017     96 in 2017     95 in 2007

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

SHORT TERM...Berislavich
LONG TERM...Kuhlman/Berislavich
AVIATION...RW
FIRE WEATHER...Kuhlman
CLIMATE...18

NWS Phoenix (PSR) Office