968
FXUS65 KPSR 171900
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1200 PM MST Tue Mar 17 2026

.KEY MESSAGES...

- A historic March heatwave through this weekend will produce
  record shattering lower desert high temperatures exceeding 100
  degrees beginning Wednesday.

- An Extreme Heat Warning will take effect Wednesday 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 WEDNESDAY/...
Strong high pressure continues to build eastward across the
Western CONUS, with the current 591-592dam anticyclone centered near
the California Channel Islands. Heat is building as the
anticyclone moves closer to the local area. This anticyclone will
move and station directly over the local area by the end of the
day tomorrow, while strengthening to record H5 height levels of
594-596dam. As has been advertised for several days, this record
strength high will lead to unprecedented record-shattering
temperatures across not only the Desert Southwest, but nearly all
of the Southwest CONUS and even parts of Northwest and Plains.

Today, high temperatures will be around 5 degrees warmer than
yesterday, with lower deserts reaching the middle to upper 90s.
There will also be a chance for a few locations to reach 100
degrees today, including El Centro and Yuma. Most lower desert
communities will eclipse the 100 degree mark tomorrow as the heat
continues to build. 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 on
Wednesday across southeast California and the rest of the area
starting Thursday.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Models all agree this ridge will become the strongest ridge the
Southwestern U.S. has ever experienced during the month of March
and potentially even during the entire winter/early spring time
frame. H5 heights are now forecast to peak at around 595-596dm on
Thursday before gradually lowering Friday and through the weekend
as the ridge center barely moves. NBM forecast temperatures are
still showing highs peaking on Friday and Saturday between 103-109
degrees across the lower deserts, which is between 7-10 degrees
above daily records. Widespread high-end Moderate HeatRisk to low-
end Major HeatRisk will impact the area from Thursday through at
least Saturday before the weakening ridge finally allows
temperatures to start to decrease.

The ridge will continue to weaken this weekend, especially by
Sunday as a it is likely to get flattened from a passing shortwave
trough well to our north. H5 heights are expected to fall to
around 582- 585dm by Sunday and mostly stay in that range through
the first part of next week. Even with these lower heights, they
will still stay above the 90th percentile of climatology.
Temperatures will be slow to drop off due to no actual front
moving through the region and only relying on the gradual
weakening of the ridge. Forecast temperatures still have highs
topping 100 degrees Sunday and easily into the upper 90s next
Monday. The weather pattern into the middle part of next week is
likely to keep slight ridging in place resulting in continued dry
weather while maintaining well-above normal temperatures mostly in
the low to mid 90s.

&&

.AVIATION...Updated at 1710Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT;
No significant aviation weather issues will exist under FEW to at
times SCT high cirrus. Winds will continue to follow their typical
diurnal tendencies. Confidence is good that winds will switch out
of the west between 20-22Z, then return to an easterly direction
late in the evening (04-06z). Speeds will generally remain under
10 kts.

Southeast California/Southwest Arizona including KIPL and KBLH:
Winds will vary between W and NNE with speeds generally AOB 6 kts.
Periods of variability are likely. Expect FEW-SCT cirrus decks
through much of the day, eventually becoming SKC this
evening/overnight.

&&

.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 25-30 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 near 10% today before readings
drop to 5-10% Wednesday through this weekend. Overnight recoveries
will not be great, with values around 20-40% through Wednesday
morning before dropping to 15-35% through the remainder of the
week.

&&

.CLIMATE...

Daily record highs through the weekend:

Date      Phoenix         Yuma         El Centro
----      -------         ----         ---------
3/17     99 in 2007    101 in 2007    101 in 2007
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

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning from 11 AM Wednesday to 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 from 11 AM Wednesday to 8 PM PDT Sunday for
     CAZ561>570.

&&

$$

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

NWS Phoenix (PSR) Office