322
FXUS65 KPSR 281713
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1013 AM MST Fri Feb 28 2025

.UPDATE...
18Z Aviation Discussion.

&&

.SYNOPSIS...
Well above normal temperatures continue today before multiple
weather systems move through the region this weekend through early
next week, which will promote cooling temperatures. In fact,
temperatures are expected to briefly fall below normal for the
beginning of next week. In addition to cooler temperatures, these
weather systems will bring breezy to windy conditions to the
region and a slight chance for rain, mainly to the Arizona higher
terrain. The windy and dry conditions will lead to high to very
high fire weather conditions on Saturday for portions of south-
central and southeastern Arizona.

&&

.DISCUSSION...
Water vapor imagery and objective analysis show that the low
pressure system that brought the breezy to windy conditions to the
region yesterday is still in place over south-central AZ. However,
it has weakened which has also allowed for the winds to weaken.
This low pressure system will continue to weaken and will slowly
move into New Mexico by this evening. With the aforementioned
trough slowly moving out of our area today skies will be mostly
clear with some high level clouds moving in later this afternoon
ahead of the next weather system. This will allow for afternoon
high temperatures to warm up into the upper 70s to low 80s across
the lower deserts and in the low-to-mid 70s across the higher
terrain.

Water vapor imagery this morning also reveals a closed low pressure
system currently spinning off the coast of California, which will be
our next weather system. This weather system will move onshore
tomorrow morning and strengthen as it does leading to a tightening
pressure gradient and increased winds across our area for Saturday.
This low pressure system will move eastward through the day on
Saturday, with the center of the low being over central AZ by
Saturday evening. The highest wind speeds will be across western
Imperial County and in the higher terrain to the north and east of
Phoenix (southern Gila County and portions of eastern Maricopa and
northern Pinal Counties). Wind speeds of 20-30 mph with gusts up to
45 mph are possible in these locations. Due to these high winds, low
relative humidity (9-12%), and widespread very dry fuels a Fire
Weather Watch has been issued from 11am-6pm MST Saturday for
southern Gila County and the higher elevations of northern Pinal and
eastern Maricopa Counties. Wind Advisories will also likely be
needed for this location and western Imperial County. Breezy to
locally windy conditions are also expected across the lower deserts
with wind speeds of 10-20 mph with gusts up to 30 mph.

In addition to the breezy to windy conditions there will also be a
slight chance for light rain showers or virga showers Saturday
night, mainly across the higher terrain areas to the north and east
of Phoenix. Moisture will be a limiting factor with PWATS of 0.4-
0.5", but soundings reveal that most of this moisture will be
confined to the 700-500 mb layer. Due to the lack of moisture, PoPs
are around 20-30% for the higher terrain areas to the north and east
of Phoenix, with less than 15% across the lower deserts of south-
central AZ. If any rain does fall accumulations will be light (less
than 0.05"). Temperatures on Saturday will be in the mid 70s across
southeastern CA and southwestern AZ since they will be behind the
low pressure system by the time of peak heating. South-central AZ
and the higher terrain areas in eastern AZ will not be behind the
low by the time of peak heating, so highs are forecasted to be in
the upper 70s (higher terrain areas) and low-to-mid 80s (lower
deserts of south-central AZ).

Sunday will be a transition day in between weather systems. The
closed low pressure brining windy conditions to the region on
Saturday will be moving into New Mexico by Sunday morning with
another, stronger, low pressure system moving into northern
California Sunday afternoon. This will once again lead to breezy to
locally windy conditions Sunday afternoon, mainly across
southeastern CA and northern and western Arizona. This low pressure
system will continue to push southeastward with the main trough
pushing into the Desert Southwest Monday afternoon. As the main
trough moves through the region on Monday, breezy to locally windy
conditions are expected area wide, with the highest winds expected
in southeastern CA and the higher terrain in eastern AZ. The NBM
continues to show low-end PoPs for Monday, mainly over the higher
terrain areas. But due to limited moisture, current thinking is
that there will only be virga showers and maybe some very light
isolated showers over the higher terrain to the north and east of
Phoenix. With this stronger trough moving into the region,
confidence is high that cooler temperatures will be moving into
the region, with highs only forecasted in the mid-to upper 60s to
near 70 degrees for Monday afternoon across the lower deserts.

The trough will exit the region on Tuesday with ridging building
back in for the middle of next week. The ridging will lead to
increasing temperatures. Slight warming is expected on Tuesday with
temperatures only forecasted to rise to the upper 60s to low 70s
across the lower deserts. But by Wednesday and Thursday temperatures
are forecasted to return to near normal (the mid-to-upper 70s for
the lower deserts). With ridging building in that will cut off
any rain chances for our region. However, ensembles are hinting
that another weather system could move into the region by late
next week. There is still a lot of uncertainty with the exact
track and strength of this system, but models are currently
showing more moisture moving in with the system, however a lot can
still change.

&&

.AVIATION...Updated at 1712Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation weather concerns are anticipated until near the end of
the TAF period where gusty conditions are introduced. Easterly
winds with speeds below 10 kts will persist through early this
afternoon. Winds will then become southerly at all terminals
during the mid to late afternoon hours then transitioning back out
of the east. Tomorrow afternoon expect S/SW gusts up to 20-25kts
at all terminals. Skies will remain mostly clear with periods of
FEW- SCT cirrus passing over the region.

Southeast California/Southwest Arizona including KIPL and KBLH:
KIPL can expect gusts aob 30kts by tomorrow morning. At KBLH no
aviation weather concerns are expected through the TAF period. At
KIPL, easterly winds will persist before switching out of the west
by mid-morning tomorrow, with VRB conditions while transitioning.
At KBLH, northeast winds will become southeasterly by early this
afternoon/evening with speeds generally remaining under 10 kts.
SCT to occasionally BKN high cirrus will progress through the
region before clearing out late this afternoon.

&&

.FIRE WEATHER...
Temperatures will be well above normal again today, with highs in
the lower 80s expected across the lower deserts. Multiple weather
systems will be moving through the region this weekend into the
beginning of next week which will allow for cooling temperatures.
Temperatures are forecasted to fall below normal by the beginning
of next week with highs in the upper 60s to low 70s. These weather
systems will bring a slight chance for light rain or virga
showers, mainly to the higher terrain areas to the north and east
of Phoenix. The main impact with these weather systems will be
windy conditions. Tomorrow will see elevated to critical fire
weather conditions across the eastern district where a Fire
Weather Watch has been issued from 11am - 6pm. Wind speeds of
20-30 mph with gusts up to 45 mph is expected along with low RH
(minRH of 9-12%), and widespread very dry fuels. Wind gusts of
35-45 mph are also expected across western Imperial County with
gusts of up to 30 mph expected elsewhere across the lower deserts.
Additional weather systems will lead to breezy to locally windy
conditions on Sunday (mainly the western districts) and Monday.
MinRHs will rise to 20-30% on Sunday and Monday with good
overnight recoveries, which could help limit the fire weather
concerns.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Fire Weather Watch from Saturday morning through Saturday
     afternoon for AZZ133.

CA...None.
&&

$$

DISCUSSION...Berislavich
AVIATION...Ryan
FIRE WEATHER...Berislavich