641
FXUS65 KPSR 302049
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
149 PM MST Mon Jun 30 2025

.KEY MESSAGES...

- Extreme heat conditions expected through Tuesday across the
  lower deserts as high temperatures top out between 110-117
  degrees, with Extreme Heat Warnings in effect as areas of Major
  HeatRisk develop.

- An influx of monsoonal moisture will lead to increasing chances
  of showers and thunderstorms, mainly during the Tuesday-Thursday
  time frame across portions of AZ, with the best chances for
  activity confined across the higher terrain areas.

- A decrease in moisture will lead to a significant decrease in
  shower and thunderstorm activity during the July 4th Holiday
  Weekend along with near normal temperatures.

&&

.DISCUSSION...
Very dry air in association with a low circulation off the
California coast is beginning to retreat westward as increasing
moisture levels creep in from the southeast early this afternoon.
This increasing moisture is allowing convection to spark along
higher terrain areas, with the closest activity along the White
Mountains. While most, if not all, activity will remain east of
the region for today, the ramping up of monsoonal convection will
continue going through the middle of the week. Here locally,
Extreme Heat Warnings continue for mostly lower desert locations
through tomorrow, with central Phoenix on record high temperature
watch for today (highs in the mid-110s). Continued hot
temperatures for tomorrow is expected as the Extreme Heat Warning
will remain in effect through tomorrow evening.

The monsoonal high is currently centered generally around the
Four Corners area, as evidenced by the storm motion of nearby
convection early this afternoon. This high location will enhance
the southeasterly flow across eastern Arizona through tonight,
resulting in better positive PWAT anomalies to spread across the
region going into tomorrow and persist through Wednesday. This
ushering of moisture will also result in enhanced easterly flow,
especially along higher terrain areas, where winds could gust
upwards of 30 mph over the next couple of days (and nights).
Monsoonal moisture will peak on Wednesday, as ensembles depict a
downward trend in PWAT anomalies going into Thursday, as the
trough currently over the Eastern Pacific will progress eastward,
drying out the Desert Southwest going into the 4th of July
Holiday and into this weekend. Cooler temperatures to near or
below normal will result starting Wednesday and persist through
the rest of the week.

Diving into more specifics of day to day convective outlook
through mid-week incorporating HREF probabilities:

Today (Monday): Showers/storms limited to far eastern Gila
County, presumably due to new initiations from the convection
currently going on over the White Mountains. Little threat for
outflow winds in lower desert areas (10-30%) as convection
remains isolated in nature.

Tomorrow (Tuesday): Increasing shower/storm chances over the
higher terrain east of Phoenix (20-40%), with higher probabilities
of outflows reaching lower desert locations, with the Phoenix
metro having a 30-70% chance of outflow winds exceeding 35 mph
gusts, highest probabilities closer (eastern metro) to the higher
terrain. Current hi-res suggests outflow maintenance will be
best maintained from the easterly/northeasterly direction, thus
should outflows come out of those directions would minimize the
blowing dust impacts to be more localized. Shower/storm chances
around 10-20% for the lower deserts of south-central Arizona
Tuesday evening and into the overnight hours.

Wednesday: Higher terrain shower/storm chances peaking around
40-60%, but limited activity expected at this time into the lower
deserts, only around 15-30%, through Wednesday night. Another
round of outflow winds reaching the lower deserts would still be
in play once again during the evening hours.

&&

.PREVIOUS DISCUSSION...

As the upper-level trough traverses the Desert Southwest on
Thursday, westerly flow aloft will begin to scour out the moisture
from west to east, leading to a downtrend in thunderstorm activity
beginning Thursday afternoon into Friday with the drier airmass
remaining in place through next weekend. As a result, it is looking
likely that the entire July 4th Holiday Weekend will remain storm-
free across the region. With the decreasing heights aloft from the
approaching trough, temperatures are expected to take a noticeable
downward trend mid to late week. Temperatures on Wednesday are
expected to be near normal, before dropping a couple of days below
normal Thursday and Friday. As heights aloft increase once again
next weekend, temperatures will be on a slight upward trend,
however, remaining below 110 degrees.

&&

.AVIATION...Updated at 1740Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
Little to no aviation impacts are expected through Tuesday
afternoon. Typical diurnal wind patterns with some westerly
breeziness are expected through this evening. Starting around
midnight tonight, expect easterly winds at around 10 kts with some
gustiness at times through Tuesday morning. Winds are then
expected to shift of the south Tuesday afternoon with increased
periods of gusts up to 20 kts. Skies will remain clear to mostly
clear with some FEW to SCT decks around 15-18K feet.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation impacts are are expected through the period. West
winds will continue to prevail at KIPL, while KBLH will generally
see south southwest winds this afternoon shifting westerly later
this evening and then will be out of the north after midnight
tonight. Skies will remain clear to mostly clear with some FEW
decks around 15-18K feet.

&&

.FIRE WEATHER...
Very hot conditions will persist through Tuesday as temperatures
across the lower deserts exceed 110 degrees. MinRHs will remain
between 5-15% this afternoon with the overall wind pattern
following the familiar diurnal tendencies with some afternoon
upslope gustiness. Low-level moisture will increase Tuesday-
Wednesday, with MinRH values climbing to 20-25% across the eastern
districts. The moisture increase will also lead to increasing
chances for shower and thunderstorm activity across the higher
terrain areas of south-central AZ starting on Tuesday with gusty
outflow winds affecting the lower deserts. There will be some
initial concerns for dry lightning activity before a further
increase in moisture levels leads to a better potential for
wetting rains by midweek. Storm chances diminish by the end of the
week through next weekend as drier air filters into the region
along with a decrease in MinRH values.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST Tuesday for AZZ530>540-
     542>544-546-548-550-551-553-554-559.

     Extreme Heat Warning until 8 PM MST this evening for AZZ541-545-
     547-549-552-555-556-560>562.

CA...Extreme Heat Warning until 8 PM PDT Tuesday for CAZ562-565>567-
     569-570.

&&

$$

DISCUSSION...Young
PREVIOUS DISCUSSION...Lojero
AVIATION...Kuhlman/95
FIRE WEATHER...Young/Lojero