Forecast Discussion

Forecast Discussion for TWC NWS Office
675
FXUS65 KTWC 202122
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
222 PM MST Mon Jan 20 2025

.SYNOPSIS...

A dry system will bring breezy to windy conditions tonight through
tomorrow along with a colder temperatures through Wednesday
morning. Highs warm to near seasonable then above normal through
the remainder of the week and into the weekend. A stronger system
may arrive late this weekend or early next week, bringing colder
temperatures, breezy conditions, and chances for precipitation.

&&

.DISCUSSION...

Active flow aloft in the periphery of a central-eastern CONUS
trough will bring a shortwave through the desert southwest this
evening through Tuesday. A pressure gradient will tighten
overnight, turning winds from the northwest this evening to the
east to southeast by early Tuesday morning. Unseasonably cold air
will drop in with this shortwave, bringing chilly conditions
Tuesday and Wednesday mornings with below normal highs on Tuesday.

An overlap of the tightened pressure gradient and increased mid-
level winds will occur Tuesday morning, which is when the
opportunity for strong gusty winds in areas open to easterly
flow is maximized. In most areas (especially sheltered locations),
breezy winds of 15-20 mph with gusts to 30 mph are likely through
much of Tuesday. On the higher end, namely exposed elevated
ridges and some locations open to east winds, gusts to around 45
mph, with a few high elevation ridges potentially exceeding 50 mph
are likely. High- resolution ensemble modeling is highlighting
the difference in wind strength well between higher terrain and
more sheltered locations. As mid- level winds diminish with the
exiting shortwave Tuesday afternoon, the highest wind gust
potential will likely begin to taper off starting late Tuesday
morning.

Cold air with morning wind chills will arrive with this shortwave
tonight. As windy conditions will have a dampening effect on the
diurnal cycle, it remains a bit uncertain how cold temperatures
will get tonight. Low to mid 30s are forecast in Tucson and
westward with lows in the 20s in valleys south and east. Wind
chill values in eastern locations may drop into the teens if there
is enough of an overlap between breezy winds and dropping
temperatures, but again the floor of this potential is uncertain.
Greater chances for colder morning lows will arrive Wednesday
with southeastern Arizona on the back side of the trough and
winds having diminished. Sub-freezing temperatures are very likely
across most of southeastern Arizona outside of far western Pima
County (though a few exposed higher elevation locations, such as
the Catalina foothills area, may still see a lingering easterly
breeze that keeps temperatures a bit warmer). Sheltered locations
in Tucson and west should see lows drop into the 20s, with lows in
valleys eastward down to the lower teens.

Mid-level height rises behind the exiting shortwave will see
temperatures quickly jump through the second half of the week. By
Friday, above normal highs in the 60s in eastern valleys and 70s
Tucson westward are likely. Looking towards the end of this coming
weekend, most guidance is in good agreement with a shortwave
dropping south through the west coast and deepening over the
desert southwest. The amplitude and placement however have
moderate inconsistencies, leading to uncertainty in precipitation
potential/timing. Some solutions produce a more progressive trough
which brings precipitation chances as early as late Saturday,
while others close the low northwest of the area and delay any
potential into early next week. This provides similar uncertainty
in temperature trends and wind potential, however colder
temperatures arriving again late this weekend or early next week
is a reasonable outcome.

&&

.AVIATION...

Generally starting SKC with increasing cirrus AOA 20k feet through
the forecast period. Northwest winds this afternoon become
northerly then east to southeasterly through tonight. Wind speeds
generally 11-18 kts with gusts 20-25 kts through 21/12Z, then
increasing to 14-22 kts with gusts up to 35 kts through the
morning. Winds gradually diminish through Tuesday evening. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...

A dry system moves through the region tonight and tomorrow,
bringing cooler temperatures and windy conditions. Brief periods
of near critical fire weather conditions possible tomorrow. Winds
shift from the northwest this evening to the east- southeast
through Wednesday morning. Gusty east to southeast winds are
likely in areas exposed to that wind direction, especially late
tonight through Tuesday morning. Exposed ridge tops and areas open
to easterly flow may see gusts as high as 40-50 mph. Winds then
gradually diminish through Tuesday evening. Minimum relative
humidities in the valleys will be 8-14 percent through tomorrow,
then 5-10 percent through the remainder of the week. Mountain
minimum humidities in the 7-14 percent range through the week.

&&

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

$$

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NWS TWC Office Area Forecast Discussion