278
FXUS65 KTWC 190855
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
155 AM MST Sun Jan 19 2025

.SYNOPSIS...Below normal high temperatures will continue through
Tuesday, along with cool mornings. Breezy easterly winds Monday
night into Wednesday. Highs warm to around seasonable levels the
second half of the week, with above normal temperatures to start the
weekend. Dry conditions persist through at least Friday.

&&

.DISCUSSION...Very little change in the short term versus 24 hrs
ago. Cool northwest flow aloft will prevail across the area through
Monday as a highly amplified ridge develops off the west coast. The
flow will turn more northerly late Monday and Tuesday as a system
drops southward through the Intermountain West to our east. During
the second half of the week, the upper ridge shifts eastward across
the western United States.

High temperatures will be 1-4 degrees below normal through Monday,
then 6-10 degrees below normal Tuesday. Low temperatures across the
lower deserts including the Tucson Metro will be in the lower to mid
30s through Monday morning. The typical cold spots in eastern Santa
Cruz, the San Pedro River valley and the Sulphur Springs valley will
dip down into the mid teens to lower 20s. Winds shift around to an
easterly direction Monday night into Wednesday, with gusty east to
southeast winds in locations prone to easterly winds, especially
Tuesday morning.

The highest threat for overnight low temperatures dipping below
freezing across the lower deserts and the Tucson Metro will be next
Tuesday and Wednesday mornings. NBM probabilities currently show the
Tucson International Airport having a 50% chance of temperatures at
or below 32 degrees Tuesday, increasing to an 80% chance Wednesday
morning. Probabilities for hard freeze conditions (28 degrees or
lower) in the Tucson Metro are 10% Tuesday morning and 25% Wednesday
morning. Tuesday and Wednesday morning low temperatures will be
highly variable with the stronger easterly winds. Locations exposed
to the wind may remain above freezing, while those locations that
are sheltered may dip down into the 20s.

During the second half of the week, the west coast ridge shifts
eastward across the western United States leading to warmer
temperatures and highs topping out right around seasonal normals
Wednesday and Thursday. Highs warm to above normal levels Friday and
Saturday, with highs in the 60s across eastern valley locations and
in the lower to mid 70s from Tucson westward.

The Ensembles, Cluster Analysis and even the deterministic GFS/ECMWF
are all coming into consensus with troughing across the desert
southwest late next weekend into early the following week. There are
significant differences between the models regarding the strength,
track, depth, amount of moisture, etc. For now, cooler temperatures
and breezy conditions look more certain with this trough. There may
potentially be a chance for precipitation across southeast Arizona
with this system, but those details will come more into view over
the next couple of days and subsequent model runs.

&&

.AVIATION...Valid through 20/12Z.
Clear skies/SKC conditions to SCT clouds AOA 20k ft AGL thru the
forecast period. SFC wind 12 kts or less thru the forecast period,
favoring a WLY/NWLY direction during the afternoon/early evening
hours and variable in direction at other times. Aviation discussion
not updated for TAF amendments.

&&

.FIRE WEATHER...Dry conditions will prevail across southeast Arizona
through at least Friday. 20-foot winds will be 15 mph or less today.
Elevated west to northwest winds are expected east of Tucson Monday,
with wind speeds of 15-20 mph and gusts around 30 mph. Winds then
shift around to an easterly direction Monday night through Wednesday
morning, with gusty east to southeast winds in locations exposed to
that wind direction especially Tuesday morning. Min RH values in the
valleys will be 8-14 percent through Tuesday, lowering to 5-10
percent Wednesday though Friday. Min RH values in the mountains will
be 10-20 percent through Tuesday, lowering to 7-15 percent Wednesday
through Friday.

&&

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

&&

$$

Zell

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