Severe Thunderstorm Warning 110, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
124 PM MST Sat Oct 11 2025

.SYNOPSIS...Deep tropical moisture will remain over the area into
Monday, along with widespread shower and thunderstorm chances. The
prolonged period of rain will result in rises across main stem
rivers and a Flood Watch is in effect. Rain chances diminish Tuesday
and dry conditions are expected areawide the second half of next
week. After today, high temperatures will be below normal through
all of next week.

&&

.DISCUSSION...The large scale pattern has a trough along the west
coast, a ridge of high pressure extending from central Texas
northeastward into the Great Lakes region and Tropical Depression
Raymond near the tip of the Baja Peninsula.

Deep tropical moisture resides across the forecast area, with PWAT
values at 200-300 percent of normal. Normal PWAT values for this
time of year are approximately 0.60 inches, with the last three KTWC
upper air soundings coming in 1.65, 1.42 and 1.60 inches, which were
all maximum daily records for those dates. These high moisture
values will continue through Monday as Tropical Depression Raymond
continues to track to the north-northwest at 13 mph and brings in a
reinforcing shot of deep tropical moisture up the Gulf of California
and Sonora, Mexico into southern Arizona.

While this moisture alone would produce widespread bands of showers
and isolated thunderstorms (which we have seen spread from west to
east across the forecast area over the last 24 hours), the threat of
heavier precipitation over the next several days will result from
the approaching trough as it interacts with this deep moisture, with
the trough digging south and then east across the western United
States.

The current forecast/most likely storm total rainfall amounts
through Monday are in the 1-2 inch range for much of southeast
Arizona, with localized higher amounts of 3-4 inches along the
International Border and in the Sky Island Mountains. The low end
model scenario (25th percentile) has 0.30-0.80 inches across most of
the area, with 1.0-1.5 inches along the International Border from
Nogales eastward, while the high end model scenario (90th
percentile, or a 1 in 10 chance of occurring) has widespread 2-3
inches, with localized higher amounts of around 5 inches along the
International Border from Nogales eastward.

The latest EMC's GEFS plume analysis for Tucson has a mean of 1.4
inches through Monday, with most of the solutions clustered between
1-2 inches, which matches up well with the current forecast. WPC
continues to highlight portions of the forecast area in slight risk
of excessive rainfall today through Monday. With the current
forecasted rainfall amounts there will likely be areal flooding
concerns and the potential for flash flooding in the heavier
rainfall bands and thunderstorms, as well as stream/main stem river
rises. Given all of this, a Flood Watch continues in effect for most
of southeast Arizona through 5 pm MST Monday. Refer to the PHXFFATWC
product for more information on the Flood Watch and to the HYDROLOGY
section below for hydro concerns.

Drier conditions return to the forecast area starting Tuesday, with
only a slight chance of precipitation across Graham and Greenlee
counties and then dry conditions areawide on Wednesday. Near normal
high temperatures today, with high temperatures lowering to 3-7
degrees below normal Sunday through the end of next week.

&&

.AVIATION...Valid through 13/00Z.
Generally BKN-OVC clouds at 5K-8K ft AGL thru the forecast period,
along with scattered to numerous -SHRA/-TSRA. MVFR conditions
possible in the -SHRA/-TSRA due to lower visibilities and ceilings.
SFC wind SLY/SWLY at 8-14 kts with occasional gusts to 20-25 kts,
becoming SELY/SLY aft 12/03Z. Aviation discussion not updated for
TAF amendments.

&&

.FIRE WEATHER...Near normal high temperatures today will lower to
3-7 degrees below normal through all of next week. Tropical moisture
in place will result in widespread showers and isolated
thunderstorms through Monday. There will be the potential for
widespread rainfall totaling 1-2 inches across much of southeast
Arizona through Monday, with higher amounts along the International
Border. Drier conditions start to move in Tuesday. Minimum RH values
will be at least 35+ percent in the valley's, with higher values in
the mountains into Tuesday. Min RH values lower into the 18-25
percent range in the valleys the second half of next week. 20-foot
sustained wind speeds will generally be 15 mph or less through next
week, with occasional gusts to 20-25 mph.

&&

.HYDROLOGY...Runoff from the expected rainfall this weekend into
early next week will bring rises to the main stem rivers/creeks
across southeast Arizona, with some of them potentially rising 3 to
8 feet. The main areas of concern will be the San Pedro River,
Nogales Wash and the Santa Cruz River. The latest forecast from the
CBRFC shows the San Pedro River at Palominas (SPPA3) nearing action
stage on Monday due to large runoff from the basin in Sonora,
Mexico. Otherwise, normally dry washes and low water crossings will
have water flowing through them.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Monday afternoon for AZZ501>509-511>515.

&&

Zell

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