Scottsdale, Arizona Weather Forecast Discussion

605
FXUS65 KPSR 221120
AFDPSR
Area Forecast Discussion
National Weather Service Phoenix AZ
420 AM MST Mon Sep 22 2025
.KEY MESSAGES...
- Showers with embedded thunderstorms will continue through this
  morning, mainly across the western deserts, before conditions
  dry out area-wide by this afternoon.
- Mainly dry conditions will prevail through the middle of the
  week before a low pressure system brings increased shower and
  thunderstorm chances once again by the end of the week.
- Near to slightly below normal temperatures today will warm to above
  normal levels by the middle of the week, then likely cool below
  normal by the end of the week and next weekend.
&&
.SHORT TERM /Today through Wednesday/...
Early morning water vapor satellite imagery depicts an upper-level
low situated more than 400 miles west of San Diego. Downstream of
this upper-level low, a northeast to southwest oriented jet streak
located over the southern Great Basin is aiding in sustaining an
expansive band of showers with embedded thunderstorms between
Imperial, Yuma, La Paz, and northwest Maricopa Counties. With the
assistance from the jet-forced ascent, hi-res models are in good
agreement in showing the shower activity continuing into the morning
hours. Rainfall intensity for the most part should remain on the
light to moderate side with very localized heavier pockets where
there are embedded thunderstorms. The activity should end by
later this morning into this afternoon as the jet-forced ascent
lifts to the east northeast. Afternoon high temperatures today
will be near to slightly below normal with readings in the mid
90s across the western deserts where there will be more persistent
cloud cover with slightly warmer readings in the upper 90s to
around 100 degrees across the south-central AZ lower deserts.
Heading through the middle of the week, the upper-level low will
remain cutoff from the main jet stream energy and meander off the CA
coast. The positioning of the cut-off low off the CA coast in
conjunction with another upper-level low that will dive through the
central CONUS will cause the subtropical ridge to amplify over the
Desert Southwest, forming an omega blocking pattern. With the region
under the influence of the subtropical ridge, increasing subsidence
aloft and decreasing moisture levels will lead to near zero rain
chances across the lower deserts with only slight chances across the
higher terrain areas of eastern AZ where there will be enough low-
level moisture available to spark a few afternoon isolated storms.
Under the influence of the ridge, 500 mb height fields will
steadily rise, peaking at around 590-592dm during the Wednesday-
Thursday timeframe. As a result, temperatures will be on the rise
starting Tuesday with highs above 100 degrees, peaking on
Wednesday close to 105 degrees for many areas with the latest NBM
deterministic showing central Phoenix approaching 107 degrees.
With temperatures in the low to mid 100s, widespread areas of
moderate HeatRisk will materialize with localized areas of Major
HeatRisk appearing on Wednesday, particularly across the Phoenix
metro area.
&&
.LONG TERM /Thursday through Sunday/...
Heading towards the end of the week, the cut-off low is forecast to
migrate inland through central/southern CA and then into AZ.
However, disagreements continue amongst the model guidance in
terms of the overall track and speed of the low as it migrates
inland, which makes for a low confidence forecast by the end of
the week into next weekend as the overall track and speed will
determine the degree of moisture return and placement of upper-
level dynamics. At this time, rain chances start to increase as
early as Thursday afternoon/evening, mainly across the eastern
third of AZ, before chances extend into the lower deserts heading
into Friday due to a further increase in moisture and upper-
level dynamics. Depending on the speed of the low, rain chances
may linger into next weekend. Given the upper-level dynamics that
will be involved with the low, if enough moisture and instability
are present, then there is the potential for strong thunderstorms
and areas of heavy rainfall to materialize, particularly on
Friday. Please stay tuned to the latest forecast throughout the
week for updates.
Temperatures will still remain above normal on Thursday, in the
low to mid 100s, with the subtropical high lingering over the
region. Thereafter, by Friday and into the upcoming weekend with
the approaching low, temperatures are expected to trend downward
to below normal levels with the latest NBM showing highs topping
out in the low to mid 90s and overnight lows in the low to mid
70s across the lowest deserts.
&&
.AVIATION...Updated at 1120Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Expect a few showers within the Phoenix metro through 15Z with
quite a bit of wind variability. Winds should settle out of the
east during the latter half of the morning, but confidence is a
bit low if the showers continue to persist. Winds will eventually
fully switch back out of the west by around noon with mid level
cloud decks aoa 10kt clearing up. Generally clear skies are
expected for this evening with winds switching back to the east by
06Z.
Southeast California/Southwest Arizona including KIPL and KBLH:
Periods of mostly light showers will continue through the rest of
this morning before diminishing during the afternoon hours. Winds
will be quite variable this morning, but with a tendency to be out
of the southeast at KBLH. Winds should eventually settle back out
of the west at both terminals during the afternoon hours as
showers diminish and skies gradually clear out.
&&
.FIRE WEATHER...
Shower activity will linger through this morning, particularly
across the western districts, before conditions dry out areawide
heading into this afternoon. Dry conditions with near zero rain
chances will then prevail through midweek. A slow moving weather
system is likely to impact the region by the end of the week
leading to increasing moisture once again and potentially
additional rain chances. MinRH values will remain elevated in the
25-35% range today before dropping into the 15-25% range through
midweek with good to excellent overnight recoveries. Winds will
generally remain light with limited afternoon upslope gusts
through the next several days.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
SHORT TERM...Lojero
LONG TERM...Lojero
AVIATION...Kuhlman
FIRE WEATHER...Lojero

NWS PSR Office Area Forecast Discussion