159
FXUS65 KTWC 100920
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
220 AM MST Fri Oct 10 2025

.SYNOPSIS...Tropical moisture has settled into southeast Arizona
and this will result in isolated to scattered showers and
thunderstorms today, especially west of Tucson. Shower and
thunderstorm chances become more widespread this weekend, with a
threat for areas of heavy rain. The heavy rain threat will continue
into Monday, especially south and east of Tucson with rain chances
gradually diminishing by the middle of next week area-wide.
Temperatures transition from above normal today to below normal by
Sunday through much of next week.

&&

.DISCUSSION...Latest IR satellite imagery shows mostly clear skies
east of Tucson with mostly cloudy skies from Tucson westward. Some
shower activity with embedded thunderstorms continues to move north
out of our forecast area into into Maricopa County. This activity is
likely being aided by an ill-defined mid level disturbance moving up
to the north ahead of Tropical Storm Priscilla. Speaking of
Priscilla, it is currently located to west of the central Baja
Peninsula and is forecast by NHC to become a remnant low within the
next 24 hours as the low level center becomes disconnected with mid
level remnants that will continue to move towards the north today
into Saturday. For today, the bulk of the stronger dynamics will be
across the western and northern sections of Arizona, with areas east
of Tucson mostly dry during the daytime hours today being closer to
the influence of the mid/upper level high over west Texas. The
HREF/CAMs do increase shower activity with some embedded
thunderstorms to the west of Tucson this afternoon, with a gradual
expansion to the east during the evening and overnight hours
tonight. Overall, we`re not expecting this part of the event to be
too impactful for our forecast area with rain totals generally less
than 0.25", though a few spots under any stronger storms/heavier
rain could see up to around 0.50"-0.75".

Saturday will be an interesting day as the forecast area will be
continue to be under the influence of the broad trough across the
western US and between the exiting mid level remnants of Priscilla
and ahead of Tropical Storm Raymond (now located off the
southwestern coast of Mexico and forecast to track towards southern
Baja Saturday). With very high moisture levels in place (PWAT ~250%
of normal) and some help with lift as our region will be under the
influence of the right entrance region of an upper level jet, expect
more widespread showers and scattered thunderstorms, especially
Saturday afternoon into Saturday night, mainly from Sells eastward.
Biggest uncertainty is whether there will be enough breaks in the
clouds to increase solar insolation and help fuel a few stronger
thunderstorms capable of producing higher rainfall rates. The HREF
SBCAPE mean of 500-1000 J/KG means certainly supports that
potential. We should note that individual storm motions will still
be rather fast that will tend to limit significant rain at any
single location.

The next phase of this active period will be Sunday into Monday as
the overall threat for areas of heavy rain with embedded
thunderstorms continues across southeast Arizona, and particularly
across Santa Cruz and Cochise County as this area will be the most
likely to come under the influence of the remnants from Raymond.
However, we should note that confidence during period decreases as
there is uncertainty in just how far north and west the mid level
remnants of Raymond will be located at before shearing out.

As far as total precipitation potential in the Saturday through
Monday period, the most likely scenario is for about 1 to 2 inches
of rain (less for western Pima County) for most of the region with
locally higher amounts in the 3 inch range across the mountains and
areas near the International border in Santa Cruz and Cochise
County. These locales near the International border have greater
potential for higher amounts due to the influence from the remnants
of Raymond Sunday into Monday. The worst-case (90th percentile)
outlier scenarios are certainly much less than the eye-popping
numbers from a couple of days ago and now range from 2 to 5 inches
on average across the forecast area. WPC has outlined most of
southeast Arizona in a slight risk for excessive rainfall for
Saturday through Monday and that continues to look good. Will defer
to the next shift for potential flood watch headlines as we`d like
to continue refining the timing and locations with the highest
flooding potential and continue to watch the trends for the more
uncertain period Sunday and Monday. We should note that the
hydrology concerns will mostly be on the larger wash and river
systems rather than urban flash flooding. See hydrology section
below for additional information.

Tuesday will still have isolated shower and thunderstorms from
Tucson eastward as the area will still be under the influence of the
trough as above normal moisture levels linger. Drier air then moves
in for mid to late week.

Temperatures will be above normal today, dropping to near normal
Saturday and then below normal levels Sunday through most of next
week.


&&

.AVIATION...Valid through 11/00Z.
FEW-SCT clouds at 7K-10K ft AGL and SCT-BKN clouds at 11K-14K ft AGL
thru the forecast period, along with ISOLD -SHRA/-TSRA. SFC wind
ELY/SELY at 8-14 kts with occasional gusts to 20-25 kts. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...High temperatures will be 4-7 degrees above normal
today, falling to near normal Saturday, then 3-9 degrees below
normal Saturday through most of next week. Tropical moisture moving
northward through Mexico will result in increasing chances for
widespread showers and isolated thunderstorms through at least early
next week. There will be the potential for widespread rainfall
accumulating over several days, Saturday into Tuesday. Minimum RH
values will be at least 25+ percent in the valley`s, with values in
the Saturday through Tuesday time frame at 40+ percent. 20-foot wind
speeds will generally be 15 mph or less into the middle of next week
and gusts to 20-25 mph.

&&

.HYDROLOGY...Run-off from the rainfall this weekend into early
next week will bring rises to the main stem rivers/creeks across
southeast Arizona with main concerns being the San Pedro river,
Nogales wash/Santa Cruz river. Otherwise the normally dry washes and
low water crossings will have water flowing through them.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...None.

&&

$$


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