463
FXUS65 KPSR 121728
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1028 AM MST Thu Jun 12 2025

.UPDATE...Updated 18z Aviation Discussion.

&&

.KEY MESSAGES...

- Dry conditions with temperatures remaining 3 to 5 degrees above
  average across the region through Friday.

- A strong ridge of high pressure will build over the Desert
  Southwest this weekend, promoting the hottest temperatures so
  far this year.

- An Extreme Heat Watch is in effect from Saturday morning through
  Monday evening for high temperatures ranging from 106 to 114
  degrees across the lower deserts.

&&

.DISCUSSION...
Very little has changed since yesterday with the sub-tropical
ridge still centered west of Baja, while providing higher than
normal H5 heights of 588-590dm over our region. The dry air mass
will also remain in place allowing for continued clear to mostly
clear skies with only some passing high cirrus clouds.
Temperatures will continue to run at least a few degrees above
normal with highs mostly topping out between 104-109 degrees today
and Friday.

Models continue to show the sub-tropical ridge shifting eastward
into northern Mexico later today into Friday before moving
northeastward on Saturday, centering itself near El Paso, TX. A
subtle shift in the upper level pattern over the northern tier
states by the weekend will also allow the ridge to extend well to
the north through the central U.S., while the ridge gains some
strength. The closer proximity of the ridge to the Desert
Southwest and the slight strengthening will boost H5 heights over
our region beginning Saturday before peaking on Sunday. The
latest model run has shifted H5 heights over our region ever so
slightly lower for this weekend, but we are still likely to see H5
heights somewhere between 591-594dm on Sunday before starting to
lower by Monday. The latest NBM run has also lowered forecast
temperatures by a degree or two overall for Sunday and Monday with
Sunday`s readings likely being the highest at 110-114 degrees
across the lower deserts. As a result, the areal coverage of the
Major HeatRisk has dropped and mostly only shows up on Sunday. The
Extreme Heat Watch remains in effect due to some uncertainty
still remaining in the forecast temperatures.

Guidance is also showing a higher probability of a modest cool
down by next Tuesday as an even higher majority of members show a
dry trough moving into our region from the west. Despite the
increasing forecast confidence in this trough, there is still some
uncertainty with its strength and how much it may drop our
temperatures. For now, the NBM shows highs dropping more into a
103-107 degree range on Tuesday before already starting to trend
back higher Wednesday into Thursday. This cool down will likely
just be a brief dip in temperatures as guidance favors the ridge
to quickly build back into our region late next week with 110
degree temperatures likely returning for at least some locations.
The weather pattern over at least the next 7 days will continue
to promote dry conditions, but there looks to be some potential
for increasing moisture returning as early as next weekend.

&&

.AVIATION...Updated at 1730Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT;
Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation weather concerns will exist through Friday
afternoon under FEW-SCT high clouds. Winds will continue to
follow their typical diurnal tendencies. Periods of light and
variable to nearly calm winds are expected, especially during
diurnal transitions. In the Phoenix Metro Area, occasional wind
gusts to 15-20 kts are likely (>70% chance) this afternoon, with a
period of even stronger westerly gusts to 20-25 kts possible for
a period late this afternoon into the evening (00-04Z).

&&

.FIRE WEATHER...
Little to no change in the weather pattern through Friday will
keep temperatures 3-5 degrees above normal and humidities
seasonably low. Winds will follow typical diurnal tendencies with
periods of modest afternoon upslope breeziness (gusts to around
20 mph at times). Minimum afternoon humidity will continue to
bottom out between 8-12% with poor to fair overnight recovery
mainly between 20-35% region-wide. Temperatures are forecast to
get even hotter this upcoming weekend with afternoon highs
reaching 110 or hotter as early as Saturday across the lower
deserts as Min RHs lower in the 5-10% range. By early next week,
the arrival of a dry weather system may result in an uptick in
winds across much of the area. These gusty winds combined with
dry fuels and very low humidity could result in elevated fire
weather concerns.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Watch from Saturday morning through Monday evening
     for AZZ530>544-546>556-559>562.

CA...Extreme Heat Watch from Saturday morning through Monday evening
     for CAZ562>567-569-570.

&&

$$

DISCUSSION...Kuhlman
AVIATION...Whittock/Berislavich
FIRE WEATHER...Salerno/Kuhlman