380
FXUS65 KPSR 161726
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1026 AM MST Mon Jun 16 2025

.UPDATE...Updated 18Z Aviation Discussion.

&&

.KEY MESSAGES...

- Hot and dry weather is forecast throughout the entire week with
  the hottest days expected to be today and Thursday.

- An Extreme Heat Warning is currently in effect through this
  evening for high temperatures ranging from 109 to 114 degrees
  across the lower deserts.

- Widespread Moderate HeatRisk will be seen on Tuesday and
  Wednesday before areas of Major HeatRisk are likely for
  Thursday.

&&

.DISCUSSION...
The extreme heat conditions will continue today with the sub-
tropical ridge still dominant over the Desert Southwest. H5
heights of 592-594dm are forecast to remain in place through this
afternoon with highs easily topping 110 degrees this afternoon for
most lower desert locations, to as high as 115 degrees in a few
spots. Fortunately, a weak shortwave trough is now nearing Oregon
and northern California with guidance tracking the system across
the Great Basin and northern portions of the Desert Southwest
tonight into early Tuesday. This system will somewhat push the
sub-tropical ridge to the south of our region, but we are only
looking at a short reprieve from the worst of the heat as H5
heights only briefly drop to between 590-592dm. We are expecting
to see a few degree drop in daytime highs on Tuesday, but some
locations may still see 110 degrees, or still around 5 degrees
above normal.

After the weak trough exits well to the east Tuesday night into
Wednesday, the ridge is forecast to begin rebuilding back over the
Southwestern U.S. with H5 heights back to between 592-594dm by
Thursday. NBM forecast temperature trends for the latter half of
the week are still inching upwards with most of the lower deserts
now likely to reach 110 degrees starting Wednesday and with some
potential for the hottest locations to see 115 degrees on
Thursday. The areal coverage of Major HeatRisk has also expanded,
mainly on Thursday, with more than 50% of south-central Arizona
covered. It seems likely additional Extreme Heat Watches/Warnings
will be needed later this week. However, this next potential
period of extreme heat should not last long as guidance continues
to favor a large Pacific trough pushing into the Western U.S.
Friday into Saturday.

The timing and the depth of this trough will likely determine
whether Friday`s temperatures will be near Major HeatRisk
thresholds, but by Saturday temperatures should be dropping below
110 degrees. This trough should continue to keep lower heights
over our region into early next week with temperatures eventually
dropping to around or even a few degrees below normals. Models
have been trending toward a stronger trough as well as a slower
progression, likely keeping dry air over most if not all of our
region. Modest monsoon moisture over Mexico still tries to push
northward into far southeast Arizona by early next week, but with
the trough providing southwesterly dry flow this moisture will
have a hard time gaining any foothold within our region.

&&

.AVIATION...Updated at 1726Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
No major aviation concerns through the TAF period. Winds will
follow typical diurnal patterns but with an earlier than usual
switch to west winds (18Z). Wind speeds will continue to remain
light through the next few hours and then are expected to increase
this afternoon and evening with gusts up to around 20 kts.
Gustiness will subside after sunset. Clear skies will persist
throughout the TAF period.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation concerns will exist through the TAF period.
Winds at KIPL favor the SE until a shift to the W this evening
(00Z) with wind speeds generally light but can expect to see a
period of speeds in the low to mid teens. KBLH will maintain a S
to SW component for a majority of the period with gusts near 15-20
kts expected this afternoon into the evening (19-00Z). Outside
the gusty conditions wind speeds will be aob 10kts. Clear skies
will persist through the period at both terminals

&&

.FIRE WEATHER...
Hot and dry conditions with some afternoon breeziness will
continue early this week. Temperatures will remain above normal
with highs near or above 110 degrees each day across the lower
deserts. Wind patterns will continue to follow diurnal trends
(upslope and downvalley) with afternoon gusts up to around 20-25
mph, particularly across the higher terrain east of Phoenix.
Humidities will stay low with MinRHs between 5-10% and overnight
MaxRHs only between 15-30%. Afternoon gusts combined with the dry
conditions may lead to some elevated fire weather conditions,
especially across the higher terrain east of Phoenix. High
pressure will remain the dominant weather feature through the rest
of the week with temperatures remaining above normal through at
least Friday and afternoon MinRHs likely staying between 5-10%
each day.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST this evening for AZZ530>544-
     546>556-559>562.

CA...Extreme Heat Warning until 8 PM PDT this evening for CAZ562>567-
     569-570.

&&

$$

DISCUSSION...Kuhlman
AVIATION...Ryan
FIRE WEATHER...Smith/Kuhlman