519
FXUS65 KPSR 210455
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
955 PM MST Wed May 20 2026

.UPDATE...Updated 06Z Aviation Discussion.

&&

.KEY MESSAGES...

- Near normal temperatures will gradually warm through the weekend
  with lower desert highs reaching the upper 90s to near 100
  degrees following comfortable morning readings.

- Dry conditions will prevail through the weekend with typical
  afternoon gusts up to 15-25 mph.

- Isolated thunderstorms with a few dry lightning strikes will be
  possible over eastern Arizona high terrain early next week,
  however little to no measurable rainfall is expected.

&&

.SHORT TERM /Today through Thursday/...
Latest mid-lvl wv imagery and 500 mb streamline analysis reveals
an elongated trough positioned over the western CONUS while an
amplified ridge remains entrenched over the E Pacific well
offshore from the Pacific NW coastline. This pattern will persist
for the next several days, keeping mostly dry and tranquil weather
in place over the Desert Southwest. 500 mb heights over the
forecast area this afternoon remain between 575-576 dam which is
near seasonal levels. Under mostly clear skies and very dry
conditions, temperatures have risen into the upper 80s to low 90s
across the lower deserts. We will likely see a third day in a row
with highs below normal in the Phoenix Metro and most other desert
communities across the region. With a very dry boundary layer in
place, yet another round of comfortable overnight temperatures in
the upper 50s to mid 60s can be expected.

On Thursday, mid-lvl heights will remain largely unchanged, however
the overall boundary layer thermal profiles will moderate in response
to increased insolation and dry subsidence aloft such that H8
temperatures warm from 20C to 22C. This atmospheric response will
result in sfc highs rebounding by a degree or two from today`s
readings, but remaining right around the daily normal. Overall a
dry and benign weather pattern, typical of late may will persist
through the end of this week.

&&

.LONG TERM /Friday through Tuesday/...
The weak troughing will gradually migrate into the southern plains
late in the week as the Conus pattern becomes more progressive
allowing low amplitude shortwave ridging to temporarily build into
the SW Conus. While notable ensemble uncertainty exists in the
northern jet stream structure, particularly over the northeast
Pacific, only minimal model spread is evident across the forecast
area and confidence is very good that H5 heights in a 582-585dm
range will envelop the Southwest. As such, temperatures will warm
several more degrees into a slightly above normal range, but
certainly nothing particularly unusual for this time of year. As the
ridge axis shifts east into New Mexico later in the weekend, deeper
southerly flow and intense heating of higher terrain may encourage
shallow Gulf surges and import of marginally better moisture
profiles heading into next week.

Model uncertainty grows markedly next week as deep troughing enters
the NW Conus while a very strong subtropical jet punches into
northern Mexico, allowing some form of cyclonic flow and shortwave
troughing to develop over the forecast area. This type of pattern is
not uncommon for mid/late May transitioning season, but fine details
in timing, intensity, and moisture availability will determine the
extent (if any) of impacts across the region. General pattern
recognition suggests the increased jet ascent and cooling aloft will
promote deep mountain convection, tapping the marginally increased
moisture early next week with the preponderance of ensemble output
indicating Monday the most favored day for isolated storms. Given
the thermodynamic profiles and historical precedent with similar
systems, very little rainfall would be expected with this
convection, but rather numerous dry lightning strikes and gusty
outflow winds. Should this evolution come to fruition, the greatest
concern would be wildfire starts over the back country followed by
increasing winds midweek with the passage of stronger troughing
through the Great Basin.

&&

.AVIATION...Updated at 0455Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation concerns are expected during the TAF period. Winds
will follow light and diurnal trends with periods of variability
during directional shifts. Skies will be mostly clear with FEW
high clouds tomorrow afternoon.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns are expected during the next 24 hours. Winds
will favor light and diurnal trends with some periods of VRB
conditions during directional shifts. Skies will be mostly clear
with FEW-SCT high clouds tomorrow morning.

&&

.FIRE WEATHER...
Temperatures will gradually warm through early next week, albeit
remaining in a slightly above normal category. Dry conditions will
prevail with minimum afternoon humidity levels falling into a 5-15%
range this week, though a modest increase in moisture will result in
these levels increasing closer to 10-20% over the weekend. This
moisture increase along with an incoming weather disturbance will
lead to a slight chance for afternoon/evening storms and lightning
strikes over eastern districts high terrain. Little to no rainfall
would be expected with this activity resulting in a heightened
threat for new wildfire starts, particularly Monday afternoon. Poor
to fair overnight recovery of 20-40% will only improve slightly over
the weekend. Typical afternoon spring upslope gustiness of 15-25 mph
will be common through the period with the most pronounced gusts
over eastern district high terrain and through the lower Colorado
River valley.

&&

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

$$

SHORT TERM...Salerno
LONG TERM...18
AVIATION...Berislavich/RW
FIRE WEATHER...18/Salerno