226
FXUS65 KPSR 202302
AFDPSR
Area Forecast Discussion
National Weather Service Phoenix AZ
400 PM MST Mon Oct 20 2025
.UPDATE...
Updated Aviation
&&
.KEY MESSAGES...
- Tranquil weather conditions will persist throughout the week with
temperatures within a few degrees of the seasonal normal.
- A weather system passing north of Arizona during the middle of the
week may bring a few light showers over the Arizona high terrain.
&&
.SHORT TERM /TODAY THROUGH TUESDAY/...
We`re off to a pleasant start for the new workweek as upper level
ridging continues to promote dry, sunny conditions. Latest RAP
analysis shows 500 mb heights remaining around 588 dm over our area,
which is around the 90th climatological percentile. Temperatures as
a result will continue to run near to slightly above normal as lower
desert highs top out in the upper 80s to low 90s through the next
couple of days, while morning lows Tuesday range from the upper 50s
to low 60s. However, the synoptic pattern will change as we head
into the middle part of this week as a cutoff low currently situated
well off the coast of the northern Baja Peninsula will begin
advancing eastward toward the southern California coast. The
approaching low will lead to increasing mid and upper level moisture
from the south starting Tuesday with cloud cover increasing over the
region.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
The cut-off low is still forecast to move through south-central
California on Wednesday as it starts to weaken. The track of the low
center may eventually move across northwest or most of northern
Arizona Wednesday night into Thursday, but with little system
moisture the vort center itself will have no impact on our area.
However, guidance is still showing some modest higher level moisture
advecting into Arizona Tuesday night into Wednesday with the highest
PWATs of around 0.8" centered over south-central Arizona. This
moisture may help to spark off some high-based light showers by
Wednesday morning, but only light accumulations are expected and
they will be confined to higher terrain areas north and northeast of
Phoenix. The lower deserts may see some virga showers and some
isolated sprinkles, but measurable rainfall is very unlikely. Once
the low center moves into northern Arizona later on Wednesday, drier
air will quickly spread west to east across southern and central
Arizona. Upper level ridging will eventually move overhead by Friday
and last through Saturday before more zonal flow is likely to affect
our region Sunday into early next week. Dry conditions are expected
to last through at least next weekend will only periods of higher
level clouds from an AR affecting the northern half of California.
Temperatures for the latter half of the week into next week are not
expected to vary all that much. Thursday is still likely to be the
coolest day with highs in the lower 80s across south-central Arizona
to the mid 80s over the western deserts. Once the ridge builds back
in on Friday, highs should move more into the 85-90 degree range and
stay there at least through Saturday before returning into a normal
range by early next week.
&&
.AVIATION...Updated at 2300Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:
No weather issues will exist through Tuesday evening with an
increasing in mid/high cloud decks late in the period. Wind trends
will be nearly identical to the past 24 hours with speeds under 8kt
and extended periods of nearly calm conditions.
&&
.FIRE WEATHER...
High pressure will remain across the region through at least Tuesday
with slightly above normal temperatures. Humidities will remain
fairly stable with MinRHs mostly between 15-20% across the lower
deserts to 20-25% for higher terrain areas. Light winds are also
anticipated through at least Tuesday with directions mostly
following common diurnal patterns. A mostly dry weather system is
then expected to pass through the region on Wednesday bringing
slight chances for higher terrain light showers. The system should
also boost humidities slightly while also leading to a period of
occasional breezy westerly conditions focused on Wednesday.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
SHORT TERM...Smith
LONG TERM...Kuhlman
AVIATION...18
FIRE WEATHER...Kuhlman
NWS Phoenix Office
Tucson, AZ 
