Fountain Hills, Arizona 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

908
FXUS65 KPSR 191228
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
528 AM MST Sat Jul 19 2025

.KEY MESSAGES...

- Near to below normal temperatures will persist through the
  middle of the upcoming work week, with lower desert highs
  generally ranging from the upper nineties up to around 107
  degrees, resulting in Minor to Moderate HeatRisk.

- Chances for showers and thunderstorms should remain mostly
  confined to the eastern Arizona high terrain and southeastern
  portion of the state through the middle of the work week.

- By the latter half of the work week, conditions will dry
  further, reducing rain chances across the forecast area to near
  zero except perhaps over far eastern Gila County.

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...
A weakening upper low is shown in latest 500 mb RAP analysis
centered along the international border, just now passing into
SoCal, with drier air along its eastern flank being funneled
northward over Western AZ and Southeast CA. Global guidance has
trended the position of this low further south in recent runs
(global models famously have a difficult time with the exact
placement of these closed lows), and so it is now expected to
meander over far Southern CA through much of the weekend.
Meanwhile, midlevel anticyclonic flow will begin to impinge on
eastern AZ during the weekend, helping to keep in place PWATS
around 100-120% of normal for the time of year over eastern AZ.
The resultant flow over South-Central AZ will vary between SSW-
SSE, causing subtle moisture fluctuations, dependent upon how
quickly the upper low weakens, its exact position, and how far
west the midlevel anticyclone impinges.

With the latest update to the positioning of the closed low over
SoCal, a few aspects of the forecast for the weekend have come
into better focus. Under mostly clear skies this afternoon and
average H5 heights for the time of year (589-591 dam), lower
desert highs should achieve readings near normal, between
102-108F. However, midlevel moisture and debris clouds from
upstream thunderstorm activity this afternoon over Sonora and
Southeast AZ will stream over South-Central AZ overnight into
Sunday, with CAMs even picking up on the possibility of an MCV
forming over Sonora this evening and its remnants passing through
Sunday mid-late morning. The resultant cloud cover Sunday should
help keep temperatures around 5 degrees below normal across
South-Central AZ, in the upper 90s to lower 100s.

Latest HREF guidance shows meager instability across the forecast
area through Sunday, confined mostly to the eastern AZ high
terrain, and so the likelihood of thunderstorm impacts remains
minimal. With abundant mid-level moisture Sunday and the possible
remnant MCV passing through, virga or even a few light showers may
develop across South-Central AZ.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/... The latest NBM guidance
continues to advertise the best precipitation chances across
South-Central AZ (as high as 15-20% over the lower deserts)
focused on Monday/Monday night. However, the synoptic setup is not
particularly favorable to justify this, and continued midlevel
moisture and debris clouds streaming up from prior day convection
over Sonora would inhibit convective potential. One explanation
for the higher PoPs could be the upper low beginning to eject
northeastward, dragging an axis of positive cyclonic vorticity
across the area, before the low gets absorbed by a midlevel trough
that dips into the Pacific Northwest early next week. The Pacific
Northwest trough is then advertised to split off of the northern
stream and retrograde offshore, settling off the CA Coast midweek.
During this time, the proximity of this trough will act to
suppress heights aloft and strengthen deep SW flow over the
region, resulting in ensemble mean PWATS dropping to around 50% of
normal by the latter half of the upcoming workweek and further
suppressing rain chances. The latest NBM continues to show
afternoon highs near or even a few degrees below normal through
midweek. This should keep the HeatRisk over our area anywhere from
high-end Minor to low-end Moderate. By late week, ensembles
advertise the center of negative height anomalies offshore
weakening, allowing the subtropical high to rebuild over the
Desert Southwest. With this evolution in mind, expect daily highs
to trend above normal by the end of the work week.

&&

.AVIATION...Updated at 1051Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
No major aviation concerns are expected during the TAF period.
Light southeasterly winds early this morning should switch back to
the west by late morning with mid and high level clouds scattering
out some. Late this evening or after midnight tonight should bring
another round of BKN higher level clouds and maybe some isolated
virga showers. Winds should eventually switch back to the east
well after midnight, partially due to distant shower-induced
outflows and also from nighttime downsloping off the mountains.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns are expected over the next 24 hours. Winds
will continue to favor a southerly component.

&&

.FIRE WEATHER...
Shower and thunderstorm chances will remain mostly confined to
the South-Central Arizona high terrain east of Phoenix this
weekend, with perhaps a slight increase in chances (15-20%) for
the lower deserts Monday. Afternoon MinRHs will be around 12-20%
for most areas and nearly every day through the middle of the
upcoming workweek. Overnight recoveries will vary generally
between 25-45% tonight except up to 50-60% in the Yuma/El Centro
areas, and values should increase to around 40-60% areawide by
Sunday night. Winds should mostly follow diurnal patterns with
only light periodic breezes in the afternoons and early evenings,
with peak gusts mostly between 15-25 mph.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

SHORT TERM...Whittock
LONG TERM...Whittock
AVIATION...Kuhlman
FIRE WEATHER...Whittock/Benedict