Tacna, Arizona Weather Forecast Discussion

074
FXUS65 KPSR 190947
AFDPSR
Area Forecast Discussion
National Weather Service Phoenix AZ
247 AM MST Fri Sep 19 2025
.KEY MESSAGES...
- Lingering shower and thunderstorm chances will continue today
  with the activity mostly focused on Arizona terrain features.
- Additional chances for mostly shower activity will become
  possible for Sunday into Monday.
- Near to slightly above normal temperatures are expected across
  the area over the next several days before a warm up is possible
  by the the middle of next week.
&&
.SHORT TERM /TODAY THROUGH SATURDAY/...
Early morning scattered showers and thunderstorms are expected to
gradually diminish by sunrise with waining upper level forcing and
continued drying from the southwest. The main upper level
shortwave trough has now pushed into central California with the
trailing trough axis now moving northward into central Arizona.
By this afternoon, PWATs are forecast to lower to near 1.0"
across southeast California, but still hover near 1.5" across
south-central and eastern Arizona. This lingering moisture should
be enough for additional showers and thunderstorms to develop
during the afternoon hours, but with the lack of upper level
support it should mostly be confined to higher terrain areas north
and east of Phoenix. Instability is likely to high enough this
afternoon for a couple of strong storms, but the threat for heavy
rainfall and flooding will be reduced from what we saw yesterday.
By tonight into Saturday, upper level ridging will take over from
the south providing for a dry day on Saturday and highs topping
out at around 100 degrees across the lower deserts. Saturday will
also see the deepening of the upper level trough off the
California coast which now guidance is trending toward affecting
our region later Sunday into Monday.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
The weather pattern for early next week remains fairly
complicated as the upper level low that develops to our west is
forecast to become cut off from the main flow. Cut-off lows are
typically very difficult for models to forecast and this is no
different. Models over the past couple of days have trended to
hold onto the cut-off low bringing it into or at least close to
our region later Sunday into Monday. The past couple of model runs
have at least shown better consensus between the GEFS and the EPS
with the low center nearing the southern California coast by
Monday before it likely slowly lifts northward on Tuesday as it
weakens.
Despite better model consensus with the positioning of the cut-off
low, there are still differences with the amount of moisture and
rain chances for our region. Both models do at least show some
agreement with light rain chances spreading across southeast
California into western Arizona during the day Sunday, but the
GEFS shows rain also affecting much of the rest of southern
Arizona while the EPS does not. Either way any rain that does
occur is likely to be fairly light with both ensemble suites
showing at most 0.1-0.2". NBM PoPs have increased across the
majority of the area for later Sunday through Monday, but PoPs are
mostly staying between 20-30%. It will probably take another day
or so to have a better handle on these upcoming rain chances, but
for now it is not looking like there will be any big impacts.
Since models are trending toward having the cut-off low move near
or into southern California early next week, the upper level
ridge should also get pushed back to the east and south. As a
result, forecast temperatures have been dialed back a good amount.
A couple of days ago, the NBM was showing 105 and 108 degrees for
Phoenix on Monday and Tuesday, but now it has lowered to 97 and
103 degrees. Eventually, the cut-off low is expected to shift more
into the Great Basin region by next Wednesday or Thursday allowing
higher heights to build back over our region. This should allow
for temperatures to warm up a bit further with NBM showing highs
likely reaching 100 degrees again across the entirety of the
lower deserts.
&&
.AVIATION...Updated at 0553Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The primary weather concern during the TAF period is the ongoing
isolated shower and storm activity, how long it goes on through
the overnight, and any additional shower and storm activity
tomorrow evening. Isolated shower and storms will continue over
the next few hours, with most activity expected to end around 08Z.
However, it could linger longer into the overnight hours. Dry
conditions are then expected through the remainder of the TAF
period. However, some additional shower and storm activity is
possible tomorrow evening but confidence is too low to include in
the TAFs at this time. Winds will go southeasterly after this
outflow moves through and then stay southeasterly through the
early afternoon prior to the usual westerly shift around 19-21Z.
Models hint at another outflow from the southeast tomorrow night,
around 03-04Z, which will make the shift to southeast earlier
than usual. Wind gusts into the 20-25kt range are expected with
the outflow boundaries, otherwise wind speeds will be aob 10 kt.
SCT- BKN clouds will clear out through the overnight hours with
SCT mid-level clouds hanging on through the rest of the TAF
period.
Southeast California/Southwest Arizona including KIPL and KBLH:
Winds at KIPL will be light and variable through the TAF period.
At KBLH, current NE`rly winds will become light and variable
around 08Z and continue into tomorrow afternoon before going
southerly during the afternoon and then westerly in the evening.
Speeds will be aob 10 kt through the period. Skies are clearing
out but FEW clouds with bases aoa 8 kft remain in the area. FEW
clouds with bases aoa 8 kft are expected again tomorrow afternoon.
&&
.FIRE WEATHER...
Drying conditions will be seen into the weekend, but lingering
moisture today over the eastern districts will provide for
continued chances for showers and thunderstorms mainly focused
over the Arizona high terrain. Despite moisture levels overall
decreasing, humidities will stay elevated through the weekend with
MinRHs mostly staying above 25-30%. Winds will remain rather
light and mostly follow diurnal directional trends. Another round
of rain chances may enter the picture by early next week with a
low pressure system nearing the region from the west. This system
should help to keep temperatures closer to normal and humidities
fairly elevated through Monday. Drier conditions should then
fully take over by the middle of next week as high pressure is
likely to become more dominant across the region.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
SHORT TERM...Kuhlman
LONG TERM...Kuhlman
AVIATION...Berislavich
FIRE WEATHER...Kuhlman

NWS PSR Office Area Forecast Discussion