Freeze Warning 1, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
350 PM MST Sun Feb 2 2020

.SYNOPSIS...Gusty winds on Monday as a weather system moves across
the area. Expect scattered valley rain and mountain snow showers
especially east of Tucson through Tuesday, but precipitation amounts
will be light. Much colder temperatures will also occur Tuesday into
Wednesday, with a hard freeze likely Tuesday night. Dry conditions
with a warming trend will then prevail Thursday into next weekend.

&&

.DISCUSSION...Upper trough over the Pacific Northwest and Great Basin
this afternoon will move eastward into the intermountain west and
southwest CONUS on Monday. Various 02/12Z models have generally
trended downward with precip chances associated with this system,
especially from Tucson westward. However, the official forecast
continues with scattered valley rain and mountain snow showers
Monday, with the best precip chances northeast of Tucson. Any precip
amounts will be quite light, with rain amounts under 0.10 inch, and
snow accumulations to perhaps 1-2 inches at the highest peaks.

The main impact from the system on Monday appears to be cooler
temperatures, but particularly breezy to windy conditions. The
strongest winds should occur southeast of Tucson. As such, the
inherited High Wind Watch was changed to a Wind Advisory that is in
effect from 10 am to 7 pm MST Monday. Please refer to AWIPS product
PHXNPWTWC /WMO header WWUS75 KTWC/ for detail. Winds will diminish
Monday evening.

The upper trough is progged to become quasi-stationary over the Four
Corners region Monday night into Tuesday. The models suggest that
moisture will be adequate to support isolated to scattered valley
rain and mountain snow shower east of Tucson Monday night into
Tuesday. Snow levels by Tuesday afternoon should fall to valley
floors east of Tucson. Thus, would not be surprised if snow
accumulations around 1 or perhaps 2 inches briefly occur especially
closer to the New Mexico state line before precip ends Tuesday
evening.

Much colder temperatures will prevail Tuesday through Wednesday as
the flow aloft becomes increasingly northerly, and as the upper
trough moves eastward into the central/southern Rockies. The various
02/12Z guidance suggests a few degrees of warming Monday night/
Tuesday morning versus previous guidance. Thus, forecast confidence
is fairly low at this time regarding the inherited Freeze/Hard Freeze
Watch for Monday night/Tuesday morning.

However, forecast confidence is quite high that a widespread Hard
Freeze will occur Tuesday night into Wednesday morning. This period
may have the highest impact, especially for the Tucson metro area,
where low temperatures around daybreak Wednesday should generally
range in the lower to mid 20s.

Thereafter, northwesterly flow aloft Thursday through Saturday will
bring dry conditions with a warming trend. The focus of attention by
next Sunday turns toward a strongly digging upper low over the Great
Basin/central California region. The flow aloft across southeast
Arizona will become increasingly southwesterly ahead of this system.
However, precip-free conditions are forecast to continue next Sunday
with above normal daytime temperatures.

&&

.AVIATION...Valid through 04/00Z.
Scattered valley -SHRA and mountain -SHSN especially east of KTUS
Monday. Otherwise, SCT-BKN clouds above 20k ft MSL this evening then
cloud decks lowering to 10k-15k ft MSL late tonight and continuing
into Monday afternoon. Surface wind sely to swly 8-18 kts with gusts
to 25 kts tonight, then surface wind swly to nwly 10-25 kts with
gusts of 25-40 kts Monday. The strongest speeds should occur Monday
afternoon, and the highest speeds should also prevail southeast of
KTUS, and particularly in vicinity of KFHU and KDUG. Surface wind
diminishing shortly after valid period. Aviation discussion not
updated for TAF amendments.

&&

.FIRE WEATHER...Gusty southwest to northwest winds Monday as a
weather system moves across the area. This system will also bring a
chance of valley rain and mountain snow showers into Tuesday. The
bulk of any precipitation will be east of Tucson, and most
precipitation amounts will be quite light. Much colder temperatures
Tuesday into Wednesday followed by dry conditions, a warming trend,
and normal diurnal wind trends Thursday into next Sunday.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 10 AM to 7 PM MST Monday for AZZ507-508-512>514.

Hard Freeze Watch from late Monday night through Tuesday morning for
AZZ502-504>506.

Freeze Watch from late Monday night through Tuesday morning for
AZZ501.

Hard Freeze Watch from Tuesday evening through Wednesday morning for
AZZ502-504>506.

Freeze Watch from Tuesday evening through Wednesday morning for
AZZ501.

&&

DISCUSSION...Francis
AVIATION...Pawlak
FIRE WEATHER...Pawlak

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