906
FXUS65 KPSR 181137
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
437 AM MST Sat Apr 18 2026

.UPDATE...12Z Aviation Discussion.

&&

.KEY MESSAGES...

- High pressure over the Southern Plains will cause breezy to
  windy conditions for portions of South Central Arizona Sunday
  morning, with the strongest gusts over higher terrain east of
  Phoenix.

- Temperatures will warm this weekend, reaching 5 to 10 degrees
  above daily normals Sunday into early next week, which
  translates to widespread lower desert highs in the nineties.

- Periods of breezy to locally windy conditions and cooler
  temperatures are expected by the middle of the upcoming work
  week.

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...
Two large-scale features are apparent in midlevel water vapor
satellite imagery early this morning that will be relevant to local
weather this weekend into next week: 1) a broad upper level low over
the Northeastern Pacific that is deepening as it approaches the West
Coast, and 2) downstream ridging shifting eastward over the
Western CONUS. Ensembles remain in excellent agreement that the
upper low will settle just off the West Coast late this weekend,
with downstream ridging centering itself over the Rockies.
Meanwhile, in the wake of a departing shortwave that is now over
the Central CONUS, surface high pressure is shifting east of the
Great Basin early this morning. This area of surface high
pressure will build southward along the front range of the Rockies
later today, eventually reaching Western TX/Eastern NM Sunday
morning, resulting in a tightening of regional pressure gradients
especially late tonight (peaking around 12Z Sunday). As a result,
Hi-Res and global models are highlighting an abnormally strong
easterly wind Sunday morning, with mountain and ridgetop wind
gusts pushing 40-50 mph east of Phoenix. The breezy easterlies
should mix to the surface across south-central AZ after sunrise,
but with gusts mostly peaking in the 20-30 mph range. From an
event like this, it would not be surprising to see localized
blowing dust in the typically prone areas and hazy conditions from
lofted dust spreading further west as the day goes on.

With the influence of upper level ridging becoming more pronounced
over the weekend, lower desert high temperatures will rise from the
upper 80s to around 90F this afternoon into the middle 90s by
Sunday. Lower desert highs in the middle 90s represent values
around 5F-10F above daily normals. Morning lows may also be
unusually warm across South-Central AZ Sunday morning and even
overachieve from the current forecast, thanks to the strong E/SE
gradient winds and adiabatic warming from downsloping off the
high terrain to our east.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
The overall pattern will remain mostly unchanged Monday, with upper
level ridging still the main influence on our weather locally,
allowing continued lower desert highs in the 90s and fairly
quiescent conditions. However, the southeasterly gradient wind event
Sunday will have pulled midlevel moisture into the region, and some
of the global guidance is picking up on a weak shortwave disturbance
dislodging from the upper low off the west coast and ejecting
overtop the ridge. This weak, transient forcing coupled with remnant
midlevel moisture could be enough to spark convective showers over
the far Eastern AZ high terrain (White Mtns, possibly the Rim)
Monday afternoon.

By the middle of the upcoming work week, the pattern will begin to
shift. The upper low off the West Coast will push inland over the
Western US, albeit in a weakening phase. Ensembles are in good
agreement on this evolution, but details such as the N/S
displacement of the low and the exact timing/speed of its eastward
progression remain unclear. On a large scale, a broad area of
positive midlevel height anomalies looks to establish off the
Pacific Northwest/British Columbia with negative height anomalies
to its south and east. This is in response to a split jet regime,
where much of the Western and Central CONUS falls under the broad
cyclonic flow of the poorly defined southern stream. As a result,
we can expect cooler temperatures (likely closer to seasonal
levels, in the 80s across the lower deserts) Wednesday onward
across the forecast area, and periods of breezy to locally windy
conditions as shortwaves progress through the Desert Southwest.
The first period of increased winds will likely be Tuesday,
especially for the Western CWA, as the initial, broad upper low
moves inland and packs heights fields over the Southwest US.

&&

.AVIATION...Updated at 1135Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

No major aviation concerns are anticipated through the forecast
period. Winds will switch out of the east early this morning,
becoming elevated for a few hours with gusts into the upper teens
possible at all terminals. Winds will then gradually shift out of
the SW later this afternoon with speeds predominantly aob 8 kts.
Skies will remain mostly clear through most of the day, with FEW
to SCT high clouds arriving over the region after sunset.

Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation concerns throughout the TAF period. At KIPL,
winds will favor a W/N direction with speeds aob 6 kts. At KBLH,
expect a gradual transition from NW to NE winds with speeds also
remaining generally aob 6 kts. Skies will remain mostly clear
this morning, with FEW-SCT high clouds beginning to overspread SE
California by the afternoon.

&&

.FIRE WEATHER...
Dry and occasionally breezy conditions will prevail through the
next week. Winds will be much lighter, generally below 15 mph, on
Saturday, and then a strong easterly wind will develop across
south-central AZ Sunday morning. The strongest winds will be over
the higher terrain of the eastern districts, but shortly after
sunrise, gusts to 20-30 mph are likely to become common across the
lower elevations. Given the time of day, RH values will be above
critical levels. Still, some locally elevated fire weather
conditions may exist across south-central AZ midday through early
afternoon Sunday. Afternoon MinRHs below 15% and at times in the
single digits will be common through the next 7 days, with minor
day to day variations. Overnight recoveries will offer little
relief tonight, with values between 10-30% areawide. Overnight
recoveries improve slightly by Sunday night, but still fall in a
poor to fair category into early next week.

&&

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

$$

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

NWS Phoenix (PSR) Office