886
FXUS65 KTWC 050912
AFDTWC
Area Forecast Discussion
National Weather Service Tucson AZ
213 AM MST Fri Sep 5 2025
.SYNOPSIS...With considerable moisture in place, expect scattered to
numerous showers and thunderstorms through Saturday. The main threat
from these storms will be areas of locally heavy rain producing
isolated flash flooding. Below normal high temperatures through
Saturday. Drier conditions return starting Sunday with a return to
near to slightly above normal temperatures next week.
&&
.DISCUSSION...Partly to mostly cloudy skies early this morning from
Tucson south and eastward with mostly clear to partly cloudy skies
to the west of Tucson. Dry conditions currently prevail across the
forecast area with some shower activity to our south in Sonora. Over
the last few days, we`ve been watching what was Tropical Storm
Lorena closely. As of 2 AM PDT, the NHC issued the last advisory and
this is now a remnant low. While Lorena was always going to help
direct increased moisture into AZ, the uncertainty of the track has
played a large impact on the range of possible scenarios. The
earlier potential for defined mid level remnants of Lorena making it
into (or near) AZ resulting in higher end rain totals is now off the
table. The mid and upper level structure from the remnant low has
sheared away from the exposed low level circulation off of the Baja
California Peninsula with the heavier rain threat staying to our
south in Sonora. The latest HREF still indicates considerable cloud
cover from Tucson south and eastward today with some mainly light
stratiform rain along the Int`l border. For areas that see some
sunshine, there is still ample moisture in place for scattered
showers and slow moving thunderstorms. However, with marginal
instability and no notable triggering mechanisms, any flash flood
threat will be isolated today. Thus, in collaboration with WPC
which has lowered Excessive Rainfall Outlook to MRGL today, we`ve
gone ahead and canceled the flash flood watch to better match this
scenario. Temperatures will continue to run about 8 to 15 degrees
below normal with the coolest temperatures south and east of Tucson
where the greatest cloud cover is expected.
For tonight, we can`t rule out nocturnal activity with scattered
showers and thunderstorms. Given the moisture in place, a small
scale lifting mechanism during the evening or overnight hours will
be enough to result in elevated precipitation chances compared to a
more typical monsoon nighttime scenario.
For Saturday, with plenty of moisture in place (PWAT`s 120 to 140
percent above normal at 1.1 inches eastern areas to 1.6 inches
western deserts), there is certainly potential to interesting from a
convective perspective. The CAMs do indeed show more activity
compared to today as the combination of greater solar
insolation/increased instability and perhaps some weak lifting
mechanisms help to initiate greater convective coverage compared to
today. With that said, the WPC has lowered our area into MRGL risk
for Day 2/Saturday as well. Even though the Flash Flood Watch has
been cancelled for both Friday and Saturday, the threat for
localized flash flooding still persists Saturday so this is
something we`ll continue to keep an eye on. Temperatures on Saturday
will be about 8 to 12 degrees below normal.
As westerly flow starts to kick in on Sunday the atmosphere will
undergo a drying process. Still a slight chance of showers and
thunderstorms mainly in the White Mountains but most locales stay
dry. West to southwest flow continues next week as temperatures warm
to near or slightly above normal levels. We`re starting to see some
hints in the ensembles of a bit of a northward moisture push
especially near the AZ/NM border midweek. The current official
forecast is still dry Tuesday and Wednesday with slight chances east
of Tucson Thursday.
&&
.AVIATION...Valid through 06/12Z.
SCT-BKN 6k-10k feet with pockets down to 4k feet Isold -SHRA mainly
near KDUG for much of the forecast period. Otherwise, especially
from KTUS and points west and north, expect SCT -SHRA/-TSRA with
gusts up to 40 kts this afternoon into evening. Confidence is too
low for anything more than a VCSH mention in TAFs. Surface winds
less than 10 kts and variable outside any thunderstorm activity.
Aviation discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Minimum relative humidities well above 30
percent through the weekend. Scattered showers and thunderstorm
chances each day through Saturday, with drier conditions Sunday
onwards. Surface winds mainly light through the forecast period,
except gusty and erratic in or near any thunderstorms. High
temperatures will be below normal through the weekend then warming
back to near to slightly above normal next week.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
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