Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 302110

Area Forecast Discussion
National Weather Service Tucson AZ
210 PM MST Mon Jan 30 2023

.SYNOPSIS...A storm system off the southern California coast will
drop southeast then move east across Mexico through Wednesday. This
will bring a threat of showers to different parts of southern
Arizona at different times, tonight through Wednesday. Cooler
temperatures will also spread over the area through Wednesday. Dry
conditions with a warming trend is then expected Thursday through
the weekend.


.DISCUSSION...The long anticipated storm system is currently off the
southern California coast with a few light showers developing over
far western Pima county and areas west and north at this time. The
center of the storm will drop southeast through Tuesday and stall
for a bit south of Yuma. Then when more energy drops down the
backside of the system Tuesday night, the low center will resume is
southeast movement into Mexico Wednesday then quickly move off to
the east.

As the system approaches tonight a band of scattered showers is
expected develop over western Pima county then shift slowly eastward
late tonight into Tuesday. Late Tuesday into Tuesday evening this
band will dissipate in place as the storm resumes its southeast
movement. Part of the question is how far east do the showers make
it. Most guidance would suggest almost making it as far east as the
Tucson metro, but not quite. A few solutions including earlier HRRR
runs pushed it into the metro, the Catalina/Rincons and the Santa
Rita mountains for a few light showers. Only mildly tweaked the pops
on the eastern edge with the final result being a low (20-30%) chance
of showers in the metro Tuesday into Tuesday night. Still talking
light amounts (< 0.10) if showers do occur in the eastern part of
the band. Meanwhile across central and western Pima county amounts
could reach up to a quarter inch (central) to as much as locally
half an inch over parts of far western Pima.

As the storm pushes eastward across Mexico Wednesday, a chance
(20-40%) of showers exists southeast of Tucson with the greatest
threat being southeast Cochise county. The snow level will be around
5,500 feet in the morning rising to around 6,500 feet but given any
precipitation that occurs will be light no accumulations are
expected except over the mountains where a light coating is possible.

Cool, below normal temperatures will spread across the area through
Wednesday with highs as much as 7-10 degrees below normal.

Thursday into the weekend an upper level ridge will bring about a dry
period with temperatures warming into Sunday. Highs on Sunday should
be around 5-8 degrees above normal, meaning most valley areas will
bump into the 70s except the colder far eastern valleys which will
likely peak in the upper 60s.


.AVIATION...Valid through 01/00Z.
Breezy southwest winds will continue through 31/01z when gusts will
cease and speeds will drop to 10 kts or less. Light winds are
expected overnight shifting to the southeast between 31/04z-31/06z.
VCSH will be possible at KTUS and KOLS after 31/15z along with SCT-
BKN clouds at 3k-6k ft AGL. Winds will shift back to the southwest
once again after 31/17z at speeds of 7-10 kts for KTUS/KOLS with
slightly higher winds for KDUG at 10-14 kts gusting 18-23kts.
Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...A weather system will move slowly across the region
into Wednesday. This system will bring cooler temperatures, a chance
of precipitation and higher RH values. Any precipitation that does
occur with this system is expected to be light except across central
and western Pima county where up to half an inch is possible. Dry
and warmer conditions will return late in the week through the
upcoming weekend. There is some potential for another weather system
early next week.




Fire Weather....Cerniglia

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