San Tan Valley, Arizona 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

911
FXUS65 KPSR 271737
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1037 AM MST Fri Jun 27 2025

.UPDATE...
18Z Aviation Discussion.

&&

.KEY MESSAGES...

- Temperatures will heat up through the weekend with widespread
  Moderate HeatRisk developing across all areas by Sunday and
  lower desert high temperatures topping out between 110 and 115
  degrees for Sunday through Tuesday

- An Extreme Heat Warning has been issued for the Phoenix metro
  Sunday through Tuesday with the rest of Maricopa and Pinal
  Counties issued only for Monday.

- Dry conditions will prevail through at least the weekend, but a
  gradual increase in moisture next week is likely to lead to
  increasing chances for showers and thunderstorms for portions of
  Arizona during the latter part of next week

&&

.DISCUSSION...
Very little has changed over the past couple of days with very dry
air still remaining in place across Arizona and areas to the south
and west of Arizona. The weather pattern has kept a progressive
wave pattern across the Pacific Northwest with troughing extending
into our region. The sub-tropical ridge has stayed well to our
east and southeast with another ridge center closer to Hawaii. In
between the two ridge centers across Mexico, monsoon moisture has
been fairly plentiful with even a weak cyclonic feature currently
positioned just south of Texas.

Over the next couple of days, the weak flow pattern across
southern U.S. will allow for the ridge to briefly rebuild over
the Desert Southwest and the Southern Plains. As a result, H5
heights over our region will rise further reaching 590dm on
Saturday before likely peaking between 591-593dm later Sunday into
Monday. The near to below normal temperatures that we have seen
over the past several days will quickly change as the ridge
rebuilds over our region, pushing daytime highs to a couple
degrees above normal today and likely to near 110 degrees
Saturday. As we see the ridge reach its peak Sunday into Monday,
temperatures across the lower deserts are expected to climb to
between 109-113 degrees on Sunday before likely peaking between
111-115 degrees Monday. Areas of Major HeatRisk are expected
mainly on Monday across south-central Arizona with widespread
Moderate HeatRisk seen elsewhere and lasting through at least
Tuesday. An Extreme Heat Warning has been issued for the Phoenix
metro for Sunday-Tuesday with other locations within Maricopa,
Pinal, and portions of Gila County only for Monday. Overnight
temperatures will also get quite warm this weekend into early next
week as moisture begins to increase slightly. By Sunday night,
lows in the 80s will be very common across much of the lower
deserts with Phoenix potentially seeing 90 degree lows.

Model guidance over the past several days has been suggesting a
quick run-up in monsoon moisture into the middle of next week, but
it may have been too good to be true. This was originally
predicated upon the ridge setting up somewhere to our north or
northeast allowing for southeasterly flow into our region as early
as Monday or Tuesday and followed by deeper moisture later in the
week. The first part is largely still expected with guidance still
favoring some marginal monsoon moisture making its way into
southeast and south-central Arizona later Monday into Tuesday, but
two other things have changed. First, the expected trough (upper
low) that is going to develop off the coast of California starting
Sunday, is now favored to be stronger and closer to our region
Monday-Wednesday. If we had plentiful moisture, this would be a
good thing providing good forcing for precipitation, but in this
case it will likely hurt chances in most areas as it will likely
increase dry southwesterly flow into at least western Arizona. We
should at least see some higher terrain shower and storm chances
starting Tuesday, but it is quite uncertain when the lower deserts
will see its first chances. Wednesday very well could be a repeat
of Tuesday with any chances mainly relegated to the eastern
Arizona higher terrain, but we can`t rule out some outflow winds
and blowing dust potentially impacting the south-central Arizona
lower deserts.

Guidance was also suggesting a decent potential for deeper
tropical moisture making its way into Arizona later next week, but
trends over the past 24-36 hours have somewhat backed off on this
potential. The tropical cyclone that is likely to form to aid in
this northward moisture advection is now a bit slower and the
upper low that develops just to our west may hang out longer
providing a longer period of dry air advection into western
portions of our area. Given these recent changes within the
models, forecast moisture has dropped with only a day or two of
PWATs reaching 1.3-1.5" into southeast and south-central Arizona
for Thursday and Friday. This amount of moisture very well could
be enough for an active monsoon day, even into the lower deserts,
but the uncertainty is still too high to speculate exactly when
and where. The latest NBM PoPs do show 30% chances into the
Phoenix area by next Thursday, which seems reasonable at this
point assuming no major changes. Beyond next Friday (July 4th),
both the GEFS and EPS generally favor a return of dry
southwesterly flow through all of the Desert Southwest, mostly due
to that near persistent trough restrengthening just to our west.

&&

.AVIATION...Updated at 1735Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
No aviation weather concerns are expected through the forecast
period. Winds will continue to follow diurnal trends through
tonight. Speeds should remain mostly aob 10 kts, although
occasional gusts into the mid to upper teens can be expected at
most of the Phoenix Metro terminals through early this evening.
Winds will return out of the ESE early Saturday morning. Skies
will remain mostly clear aside from a FEW cumulus aob 15 kft.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns are anticipated through the TAF
period. Winds will gradually transition from SE to W throughout
the day at KIPL while remaining mostly S at KBLH. Overall wind
speeds will remain aob 10 kts, although occasional afternoon gusts
up to 20 kts can be expected at KBLH. Lofted smoke/haze may
occasionally affect slantwise visibilities during the late
afternoon/evening hours at KIPL.

&&

.FIRE WEATHER...
High pressure will gradually strengthen across the region through
the weekend leading to a strong warming trend and continued dry
conditions. Temperatures will warm to several degrees above
normal starting Saturday before peaking early next week. Expect
little change in humidity trends as MinRH values continue to range
between 5-15% each day and overnight recoveries stay between
20-35%. Winds will follow familiar diurnal trends with typical
afternoon breeziness, gusting mainly between 15-20 mph.
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 Warning from 10 AM Sunday to 8 PM MST Tuesday for
     AZZ537-540-542>544-546-548-550-551.

     Extreme Heat Warning from 10 AM to 8 PM MST Monday for AZZ534-
     538-539-541-545-547-549-552>555-559-560.

CA...None.
&&

$$

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