330
FXUS65 KPSR 171140
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
440 AM MST Tue Jun 17 2025

.UPDATE...Updated 12Z Aviation Discussion.

&&

.KEY MESSAGES...

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

- Extreme Heat Warnings have been issued or extended through much
  of the workweek across south-central Arizona for high
  temperatures ranging from 108 to 116 degrees across the south-
  central Arizona lower deserts.

- Widespread Moderate HeatRisk will be seen throughout the week
  before widespread Major HeatRisk prevails Thursday across south-
  central Arizona.

&&

.DISCUSSION...
The sub-tropical ridge will continue to be the dominant weather
feature through the rest of the workweek, despite a weak shortwave
trough currently tracking across the Great Basin and northern
portions of our region. This trough was originally forecast to
knock down the ridge enough to drop temperatures to below 110
degrees across the entirety of the lower deserts, but instead we
are seeing a weaker system and a track farther to the north
leading to just a few degree drop today. With H5 heights staying
between 590-592dm today, highs should only drop to between 109-112
degrees across the majority of the lower deserts. Once the
shortwave trough exits to the east tonight into early Wednesday,
the ridge will quickly rebuild back over our region pushing H5
heights back to near 594dm by Thursday. Temperatures will in turn
climb back toward the 115 degree mark across south-central Arizona
by Thursday leading to a fairly large area of Major HeatRisk
again. Despite the HeatRisk dropping into the Moderate category
today and for the most part on Wednesday, there is enough to
justify keeping the Extreme Heat Warning in place for the Phoenix
Metro today and across the rest of south-central Arizona Wednesday
through Friday.

As the ridge reaches its peak intensity on Thursday, highs are
likely to top out between 112-116 degrees across south-central
Arizona to 111-114 degrees across the western deserts. By Friday,
a large Pacific trough will begin to push into the Northwestern
U.S. This trough will gradually shift the sub-tropical ridge
eastward allowing for lowering heights over our region as early as
Friday afternoon, but more so over the coming weekend. As a
result, temperatures will also begin to lower across our area
beginning Friday, but highs at or just above 110 degrees are still
expected to be seen.

Ensemble guidance shows the trough getting fully displaced to our
east Saturday night into Sunday, quickly lowering daytime highs
back to near or even a couple degrees below normal by Sunday.
This should quickly lower our HeatRisk across the region to
either Minor or at most low-end Moderate. This large trough is
expected to stall out over the Western U.S. for several days,
likely through at least the first part of next week. NBM
temperature guidance has shifted temperatures even lower for the
first part of next week with highs mainly between 100-104 degrees
for Sunday-Tuesday. Models are also showing some moisture seeping
into southern and central Arizona starting this weekend, but it
is not expected to be enough to bring any rain chances for any
locations except for far southeast Arizona. The bulk of the
available moisture is expected to go into New Mexico where much of
the state should see decent rain chances next week.

&&

.AVIATION...Updated at 1135Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
No major aviation concerns through the TAF period under clear
skies. Winds will follow typical diurnal patterns with periods of
variability between transition periods. Afternoon and early
evening gustiness 15-20 kts out of the westerly direction will
continue to be common through the period, before subsiding through
the evening hours.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation concerns will exist through the TAF period under
clear skies. Winds at both terminals will continue to be light and
variable. At KIPL, winds will become SE`rly early this afternoon,
before going SW`rly this evening. At KBLH, winds will go W`rly
around mid-morning before going S`rly late this afternoon.

&&

.FIRE WEATHER...
Hot and dry conditions with modest afternoon breeziness will
continue over the next several days. 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. By the
weekend, a dry weather system will eventually move into the region
from the west, dropping temperatures to around normal while also
increasing MinRHs into the teens. This should also increase winds,
most likely on Friday and Saturday, with afternoon gusts of 25-30
mph possible.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST Friday for AZZ537-540>544-
     546-548>551.

     Extreme Heat Warning from 10 AM Wednesday to 8 PM MST Friday for
     AZZ534-538-539-547-552>556-559>562.

CA...None.
&&

$$

DISCUSSION...Kuhlman
AVIATION...Berislavich/Young
FIRE WEATHER...Kuhlman