975
FXUS65 KPSR 201103
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
403 AM MST Tue Jan 20 2026

.UPDATE...Updated Aviation Discussion.

&&

.KEY MESSAGES...

- High pressure will persist over the region through the middle of
  the week resulting in above normal temperatures and dry
  conditions.

- A weak low pressure system will meander its way toward the
  region by late in the week and into the weekend bringing cooler
  temps and chances for rainfall.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...
A high pressure ridge remains intact along the West Coast with
weak troughing now in place across the Desert Southwest. Despite
the change in the upper level flow for our region, we will
continue to see dry and tranquil weather conditions over the next
few days. The lower heights aloft will nudge temperatures a bit
cooler leading to highs mostly in the lower 70s starting
Wednesday. The upper level ridge will also gradually break down
over the next couple of days allowing a developing weather system
off the West Coast to reach the coast of California late Wednesday.
The strengthening of this weather system looks to be a result of
a modified sub-tropical jet branch merging with a modified polar
jet later today into tonight. The peak strength of this upper
level low looks to occur on Thursday just off the coast of central
and southern California. Guidance continues to show a slow
southeastward progression of the low into Thursday before reaching
northern Baja by midday Friday.

For our region, we are expecting higher level clouds to increase
on Wednesday into Thursday, but the lower levels will remain quite
dry through Thursday. This first batch of clouds should be at
their thickest Wednesday night and Thursday morning before much of
the higher level moisture ejects to the east. As the low nears the
coast of southern California later Thursday and Thursday night,
southerly low and mid level flow is likely to increase enough to
begin to pull moisture northward out of Mexico. Forecast PWAT
anomalies are shown to increase from normal early Thursday to
around 150-175% of normal by Friday morning.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Moisture across the area should peak from Friday afternoon through
Friday night with the best moisture likely being focused across
southeast Arizona. Model trends over the last couple of days have
leaned toward the more bullish case for this weather system
bringing rainfall to at least portions of our region. Despite the
center of the low missing our area to the south and it weakening
by the time it reaches northern Baja, we are likely to see most of
our forcing for precipitation from a combination of the upper jet
and low level orographic lift. This is not exactly an good recipe
for widespread rainfall, but it should be enough to bring a period
of mainly light showers from as early as Friday afternoon through
at least Saturday morning. Initial dry air in the low levels
should limit the rainfall during the first half of the event with
the best chances for measurable rainfall likely occurring during
the overnight hours Friday night. There are also some indications
of some weak instability during the daytime hours Saturday if the
cold core is close enough to southern and/or central Arizona. This
could lead to some additional isolated to scattered shower
activity on Saturday. Forecast rainfall for this event is expected
to be fairly light with the most recent guidance showing upwards
of a 0.10" across the Phoenix area to 0.25-0.50" for the eastern
Arizona high terrain. Since this will again be a fairly warm
weather system, snow levels are expected to mostly stay above 7000
feet.

Upper level ridging is then favored to quickly push into the
region from the west on Sunday with dry air surging in from the
north by Sunday afternoon. As high pressure and dry air settles
over the region early next week, we are likely to see the near
normal temperatures on Friday-Sunday quickly trend upward.
Guidance suggests we should see a return of above normal
temperatures by around next Tuesday or Wednesday.

&&

.AVIATION...Updated at 1105Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT and
Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation concerns under FEW cirrus cloud decks can be
expected through the TAF period. Light (generally AOB 6 kts) and
diurnal winds with extended periods of variable to nearly calm
conditions will be common. However, confidence is moderate that a
surge of E/NE winds later this morning (16-18Z) with gusts
temporarily into the teens may occur at a few of the Phoenix area
terminals.

&&

.FIRE WEATHER...
Dry conditions with above normal temperatures will persist
through mid week. Daily MinRH values are expected to remain
between 15-20% each day with overnight recoveries of 30-60%.
Winds will overall be light through the period with only some
periodic light breeziness across the Lower CO River Valley and
over the Arizona high terrain. The weather pattern will change
late in the week to allow for cooler temperatures, an increase in
humidities and rain chances by Friday or Saturday.

&&

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

$$

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

NWS Phoenix (PSR) Office