437
FXUS65 KTWC 222041
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
141 PM MST Wed Jan 22 2025

.SYNOPSIS...A brief cooling of temperatures tomorrow, then
warming to above normal Friday and Saturday. A strong storm
system moving into the region late this weekend and early next
week will bring colder temperatures, breezy conditions, and
chances for valley rain and mountain snow.

&&

.DISCUSSION...The synoptic pattern today has an amplified ridge
in the Pacific Ocean towards Alaska. There is a long wave trough
hanging across the Central Plains. This intersection of ridge and
trough has been giving Southeast Arizona northerly flow and cooler
temperatures. Tonight and tomorrow morning, we can expect to see
another round of freezing to sub freezing temperatures across the
region. Daytime temperatures will be a few degrees cooler than
today.

As the ridge axis nudges easterly, Southeast Arizona will
experience a brief warming of temperatures. This will bring some
easterly surface winds tomorrow and on Friday.

This weekend, we will start to see a pattern change. Ensemble
models agree on one thing so far, a weather system will move into
the region to bring breezy conditions and chances for valley rain
showers and mountain snow. What the ensemble members don`t exactly
agree on is the placement of the system with the secondary issue
of magnitude by the early week. It is interesting to note, the
big three ensemble model members, the GEFS, ENS, and GEPS, are
almost in their own camps of the where the low pressure center
should be and when. There are a few exceptions which the cluster
analysis helps pulls those individual members out to get a
majority consensus of how the system may unfold. Generally, the
low will develop by Friday and descend south from the Pacific
Northwest to around southern California. We can start to feel the
impacts by Saturday afternoon with moisture creeping up by the
start of the new week.

Breezy conditions will start to develop on Saturday. With the
already dry conditions, isolated areas in Southeast Arizona,
mainly south of Tucson towards the International Border can see
near critical to critical fire weather conditions. The confidence
is low due to the uncertainty of system placement to provide the
stronger gusts from tighter pressure gradient or general type of
breeze.

By Sunday, chances for rain showers and mountain snow across the
region starting will increase and stay elevated through at least Wednesday.
The bulk of the rain and snow appears to be on Monday and Tuesday
with the latest ensemble runs. Rainfall amounts will be generally
less than 0.3 inches and snow amounts 1 to 4 inches in the
mountains with the White Mountains closer 5-6 inches. Something to
look forward this weekend and the start of the new week.


&&

.AVIATION...Valid through 24/00Z.
SCT-BKN clouds at or around 25k feet AGL until 23/04Z and then
clearing from north to south. Expect SKC to remain through the end
of the forecast period. SFC winds generally NW-N around 10 kts for
the rest today becoming terrain driven and less than 8 kts in the
overnight period. By 23/18Z, winds become NE-E at 9-15 kts with
gusts up to 25 kts through the end of the period. Aviation
discussion not updated for TAF amendments.


&&

.FIRE WEATHER...Dry conditions and a small warming trend into the
early weekend. Minimum relative humidities in the valleys
will be 5-10 percent through the remainder of the week. Mountain
minimum humidities in the 7-14 percent range through the week. A
weather system will be moving through this weekend into early next
week will bringing gusty winds Saturday and Sunday, followed by a
chance for valley rain and mountain snow for the first half of
the week. There can be isolated areas of critical to near
critical fire weather conditions on Saturday due to the strong
wind gusts and the very dry conditions, mainly south of Tucson
towards the International Border. Min RH will then increase by 10
to 20 percent Sunday into early next week.


&&

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

$$

Strongman


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