214
FXUS65 KPSR 260526
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1025 PM MST Wed Jun 25 2025

.UPDATE...
Updated Aviation

&&

.KEY MESSAGES...

- Below normal temperatures will gradually warm to above normal by
this weekend, with widespread Moderate HeatRisk across all areas by
Sunday

- Dry conditions will overall prevail through the weekend with daily
light afternoon and evening breezes

- Extreme Heat Watch in effect for the Phoenix metro Sunday through
Tuesday as Major HeatRisk develops

&&

.DISCUSSION...
A decaying trough centered over the Great Basin region is ushering
in dry southwesterly flow over the region today. The main moisture
axis setting up in between this trough and the strong ridging over
the eastern half of the country is centered further east than
yesterday over eastern New Mexico, where the more robust shower and
thunderstorm activity will occur today. Hi-res models are indicating
some shower and thunderstorm activity along the far eastern portions
of Arizona, but no legitimate threat of any convection is
anticipated across eastern Gila County this afternoon and evening.
Otherwise, due to this weakening trough across western CONUS over
the next several days, expect temperatures to climb back to above
normal levels by the end of this week, with widespread Moderate
HeatRisk across the lower deserts.

Daily convection will continue across southeastern Arizona over the
next several days, but no real threat of aside from a stray shower
here or there will continue across the far eastern portions of the
forecast area. The weather pattern will transition from weak
troughing across western CONUS to the building subtropical ridge as
it retrogrades back to the west going into this weekend. This will
degrade the above normal PWAT`s in southeastern Arizona to shut off
convection over the weekend. As a result of building mid-level
heights across the region this weekend, we can expect temperatures
to continue to rise, with lower desert highs reaching or exceeding
110 degrees by Sunday. Major HeatRisk starts to develop on Sunday as
well, with the largest coverage on Monday, primarily across the
south-central Arizona lower deserts. NBM deterministic guidance
continues to increase the daily highs Sunday-Tuesday and, along with
the high confidence in this scenario occurring, has resulted in
Extreme Heat Watch issuance for the Phoenix metro for this forecast
package.

&&

.PREVIOUS DISCUSSION...
Ensemble guidance then suggests the ridge will begin to shift more
to the north, centering itself over the Four Corners area by next
Tuesday. Once this shift occurs, it should allow for the flow in the
lower levels to turn out of the southeast into much of Arizona. If
guidance is correct with pushing the high center over the Four
Corners area, it would allow for a gradual uptick in moisture across
Arizona next week and likely our first decent chances of monsoon
convection by around the middle part of next week. Some of this will
also depend on a weak trough that is shown setting up just to our
northwest. For now, there remains a good deal of uncertainty with
the placements of the high center and the trough, along with how
much and when the moisture advects into our region. We could start
to see some isolated to scattered eastern Arizona higher terrain
convection as early as Monday or Tuesday with some potential for
convection into the lower deserts as early as next Wednesday or
Thursday.

&&

.AVIATION...Updated at 0525Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
No major weather issues will exist through Thursday evening with
only afternoon clouds building over mountains well east of the
terminals. Confidence is excellent that the behavior of wind speeds
and directional shifts will be nearly identical to the past 24
hours. This includes limited directional variability and gustiness
through the entire period.


Southeast California/Southwest Arizona including KIPL and KBLH:
No significant weather concerns will exist through Thursday evening
under clear skies. Wind trends will be nearly identical to the past
24 hours including limited gustiness and extended periods of
variable directions during the morning hours. While not directly
impacting sfc visibilities, lofted smoke/haze may occasionally
affect slantwise visibilities during the morning and late
afternoon/evening hours at KIPL.

&&

.FIRE WEATHER...
No significant fire weather concerns are expected over the next few
days. Temperatures will continue to gradually warm day-to-day, but
readings should remain near to below normal through Thursday. MinRH
values will only range between 5-15% and overnight recoveries will
not offer much relief as values hover between 20-40%. Winds will
follow familiar diurnal trends with typical afternoon breeziness,
gusting mainly between 15-20 mph. By the weekend, temperatures will
warm to above normal with highs potentially peaking above 110
degrees across the lower deserts by Sunday. Eventually, the weather
pattern should become more favorable for increasing moisture and at
least some scattered high terrain showers and thunderstorms by
around next Tuesday. This may initially result a day or two of dry
lightning concerns before moisture and rainfall chances increases
later next week.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Watch from Sunday morning through Tuesday evening
     for AZZ537-540-542>544-546-548-550-551.

CA...None.

&&

$$

DISCUSSION...Young
PREVIOUS DISCUSSION...Kuhlman
AVIATION...18
FIRE WEATHER...Young/Kuhlman