Freeze Warning 1, NWS Phoenix, AZ

Area Forecast Discussion
National Weather Service Phoenix AZ
219 AM MST Sun Nov 11 2018

.SYNOPSIS...
A cold front will move through the Desert Southwest today, bringing
cooler, drier and windy conditions to the region. The cooling
trend will continue through Tuesday, with the potential for
freezing temperatures across southern Gila County Tuesday morning.
A return to above normal temperatures is expected later in the
week. The drier than normal conditions will also persist with no
chance of precipitation.

&&

.DISCUSSION...
Clear skies abound across most of the Southwest ahead of a digging
trough moving through the Great Basin. An associated low-level
cold front was moving into southern Nevada and east-central
California as of 2 AM MST. This feature will quickly progress
southward, first affecting the lower Colorado River Valley and
southeast California later this morning, and the remainder of
south-central Arizona by late this evening. Given the strength of
this front, an abrupt post-frontal wind shift out of the north
will occur, amidst 30-40 kt of 0-3 km AGL flow emanating out of
the southern Great Basin. The typical wind-prone areas across
southeast California and the lower Colorado River Valley will
experience the strongest gusts today, with gusts up to 50 mph
possible, and may cause areas of blowing dust. Fire weather
concerns will also be heightened across these areas. Winds won't
be quite as strong farther east into south-central Arizona, but
gusts to 20 mph may still be possible within the Phoenix area this
afternoon. Also of concern, some lofted smoke originating from
wildfires in California is expected to drift south-southeastward
today across southeast California and southwest Arizona, per the
experimental HRRR-Smoke output.

With the compact and progressive shortwave trough exiting the
region by Monday, wind speeds will weaken somewhat, though still
remaining breezy. Dry continental trajectories will persist
throughout the period of wave passage, precluding any precipitation
from developing across southeast California and most of Arizona.
The primary concern will shift to the cool temperatures that will
encompass the region Monday and Tuesday. In fact, the latest
forecast guidance suggests Phoenix will struggle mightily to
escape the 60s on both days during the afternoon. The first freeze
of the season is appearing increasingly likely across higher
terrain portions of southern Gila County, including the Globe
area. Thus, a Freeze Watch will be hoisted for Tuesday morning.

A loosening of the midlevel height gradient and weakening of flow
aloft will follow in the wake of the departing shortwave trough,
as midlevel ridging attempts to expand eastward. This will bring a
warming trend with temperatures to closer to seasonal normals,
with dry conditions continuing through next weekend. There are
some indications that southern stream westerlies will begin to
increase late next week from Baja California eastward, perhaps
eventually yielding the arrival of another weather disturbance
beyond the forecast period. Until then, quiescent weather
conditions look to prevail.

&&

.AVIATION...

South-Central Arizona including KPHX, KIWA, and KSDL: A cold front
moving through today will quickly switch winds to the west this
morning with gusts to around 20 kts in the afternoon.  Winds will
switch to the north to northeast this evening and may remain there
through the night.  Some uncertainty as to whether or not the
easterly component will develop overnight as models remain mixed.

Southeast California/Southwest Arizona including KIPL and KBLH:

A cold front moving through today will bring breezy to windy
conditions to the terminals.  North to northwest winds will be
strongest at KBLH today, gusting to around 30 kts in the afternoon,
with lighter winds at KIPL.  Blowing dust will certainly be a
concern at KBLH this afternoon where reduced visibilities will be
possible, and perhaps even lower than what is currently indicted in
the TAF. Beyond this, no ceiling concerns are expected as this
system will be very dry. Gusty winds look to diminish after sunset.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday:
High pressure will prevail across the Desert Southwest, resulting
in drier than normal conditions. Slightly below normal
temperatures are also anticipated with a gradual warming trend
through the week. Breezy easterly winds are likely across southern
Arizona on Tuesday before the pressure gradient weakens into the
middle of the week, resulting in a gradual decrease in average
winds.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Wind Advisory from 10 AM this morning to 5 PM MST this afternoon
     for AZZ530.

     Red Flag Warning from 10 AM this morning to 7 PM MST this
     evening for AZZ131.

     Freeze Watch from Monday evening through Tuesday morning for
     AZZ562-563.

CA...Wind Advisory from 9 AM this morning to 4 PM PST this afternoon
     for CAZ560-564-565-568>570.

     Red Flag Warning from 9 AM this morning to 6 PM PST this evening
     for CAZ231.

&&

DISCUSSION...Rogers
AVIATION...Wilson
FIRE WEATHER...Kuhlman/Wilson