146
FXUS65 KTWC 151037
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
337 AM MST Sat Nov 15 2025

.SYNOPSIS...High temperatures will remain 5 to 10 degrees above
normal today. A low pressure system is then expected to impact
the region Sunday, bringing a chance for light showers, cooler
temperatures, and breezy conditions. Unsettled conditions are
expected to continue next week along with below normal temperatures.

&&

.DISCUSSION...One last day of warm temperatures before a pattern
change ushers in unsettled weather across Southeast Arizona. The
upper pattern this morning is defined by a strong cutoff-low
positioned off the coast of southern California, and another
trough extending from the Gulf of Alaska south into the Eastern
Pacific near 36N/160W. The latest GOES precipitable water imagery
indicated an impressive, yet spatially thin, subtropical plume of
PWAT 1.50+ inches along the SE periphery of the cutoff-low this
morning, extending along the northern Baja and into the California
Bight.

This cutoff-low is expected to eject NNE into the Great Basin today
as the upper trough upstream rapidly moves SE. Although the bulk
of the lift associated with this feature will remain across southern
California and the NW half of Arizona today, a decent vortmax rotating
along the backside of the feature will round the base, tracking across
SW Arizona into central Arizona Sunday afternoon. Even though
there will be a modest amount of lower level moisture convergence
along the frontal boundary as it swings through the western half
of the CWA tomorrow, the moisture itself will continue to rapidly
mix/lower over the next 24-36 hours as it moves west across SW AZ.
The combination of all of this will result in generally light
showers moving across our neck of the woods with this system. The
15/01Z probability of rainfall in excess of 0.25 inches (the
amount necessary to impact outdoor activities with minor ponding
of water/puddles) will be between 10-20 percent across central and
western Pima/Southeast Pinal during the day Sunday...with a
higher probability between 20-30 percent along the Pinal/Graham
county border Sunday afternoon. In any event, precipitation is
not expected to be significant...with only minor impacts
anticipated. The evolution of this system will begin with a slight
chance of showers moving into the far western portions of Pima
county late this afternoon and into this evening, with scattered
showers becoming more prevalent Sunday as the frontal boundary
drags through the area from the west toward the northeast.
Although we will see a significant cool-down in temperatures
compared to yesterday (around 10 degrees), snow levels are still
expected to remain above the higher elevations through Sunday
night. The main impacts with this system may actually be breezy
conditions expected Sunday. Expect breezy southwest to west winds
15 to 25 mph with gusts to 30-40 mph Sunday, especially east and
southeast of Tucson in Cochise county.

Otherwise, this first system is expected to be clear of Southeast
Arizona Monday. However, the follow-up trough that ejected the
cutoff will take up residence in its wake...settling in off the
coast of southern California Monday night. The progressive
westerly flow of the mean upper pattern will then track this
system across Southeast Arizona Tuesday and Wednesday. This
feature will enhance the cooling that will occur this weekend,
resulting in 850-700 mb thicknesses dropping down to around 1560m
by 00Z THU. This thickness correlates to a high temperature of 60
degrees for KTUS Wednesday afternoon which would be around 15
degrees below normal. My hunch is that this cooling may finally
bring more widespread freezing temperatures to the eastern valleys
late next week. Otherwise, I would expect this system to be a
little more productive with regards to precipitation...with a
quarter to a third inch expected in the valleys and higher
amounts between a half and one inch in the mounatins. Given the
cooler airmass, we may see between 2 to 4 inches of snow Tuesday
and Wednesday above 7000 feet. Still a lot can happen with the
timing and intensity of this disturbance, but it does look like it
will have a minor to moderate impact on Southeast Arizona.

&&

.AVIATION...Valid through 16/12Z. Clear skies/SKC conditions thru
15/19Z, then SCT-BKN clouds at 7k-10k ft AGL thru the remainder
of the forecast period. Slight chance of showers west of KTUS this
evening, with ISOLD-SCT -SHRA developing overnight. SFC wind
variable in direction and less than 12 kts this morning, becoming
SLY/SWLY 10-15 kts aft 15/19Z. Aviation discussion not updated for
TAF amendments.

&&

.FIRE WEATHER...Dry conditions and high temperatures 5-8 degrees
above normal will continue through today. A storm system will
begin to move across the area from the west late this afternoon
and this evening. Showers will increasing in coverage during the
day Sunday, with embedded thunderstorms and cooler temperatures.
Breezy southwest winds of 15-25 mph with gusts to 30-40 mph are
expected on Sunday. Minimum RH values in the valleys of 20-25
percent and 25-30 percent in the mounatins today, with elevated Min
RH values through all of next week at 33-43 percent in the
valleys and 50-60+ percent in the mountains. Another storm system
is expected to move into the area Tuesday and Wednesday bringing
another round of precipitation across Southeast Arizona, along
with breezy south to southwest winds Tuesday.

&&

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

&&

$$

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