858
FXUS65 KPSR 222341
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
441 PM MST Tue Apr 22 2025

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
Dry and generally tranquil conditions will persist over the next few
days with temperatures running near to slightly above seasonal
values. A dry weather system will move off the Eastern Pacific later
this week, bringing breezy to locally windy conditions along with a
cooldown with temperatures falling below seasonal normals into
the weekend.

&&

.DISCUSSION...
500mb RAP analysis reveals weak quasi-zonal flow stretched out
across much of the Great Basin, resulting in a fairly quiet pattern
for the region. With the expectation that this pattern will not vary
much over the next few days, very little day-to-day changes will
take place at least through the middle of the week with dry
conditions prevailing and lower desert highs ranging in the upper
80s to lower 90s. Global models show a very weak disturbance moving
through the western CONUS through the middle of the week, but the
only noticeable impact with this would be the presence of breezy to
locally windy conditions in the typical spots of Western Imperial
County.

Ensembles have come into a bit more agreement regarding the
stronger area of low pressure later this week compared to 24
hours ago. Some subtle differences remain, mainly in the timing,
exact track, and amplification, but it appears that the models
have honed in on an evolution that takes the center of this system
across the Southern Great Basin by Sunday. Though this system
appears to be dry, translating to essentially zero rain chances,
it will not be without its noticeable impacts on regional
conditions. Associated height anomalies approaching 1.5-2 standard
deviations below normal vs. climatology will translate to a
decent cooling trend heading into this weekend. Even though NBM
MaxT spread remains around five degrees during the weekend
timeframe, this does not degrade the idea that regionwide cooling
temperatures are likely, with many areas potentially falling 5-10
degrees below normal for late April. The other associated impact
will be an increase in winds during much the weekend, particularly
during the afternoon and evening hours, thanks to an enhancement
of the thermal and pressure gradients. The magnitude of the winds
will be largely dependent on the track of the system, but early
indication are that gusts upwards of 25-35 mph may be common, with
advisory level gusts >=40 mph possible for the usually windy
spots of Southeast California and the Arizona high terrain. We are
several days from this low moving onshore so forecast detail
could certainly change, but if trends continue in the direction
they are, wind products may be needed later this week. Regardless
of if winds do reach advisory thresholds, the relatively warm and
dry airmass in place, combined with the enhanced winds, will
result in periods of elevated, to potentially critical fire
weather conditions at times.

&&

.AVIATION...Updated at 2340Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT and
Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation weather concerns under clear skies can be expected
throughout the TAF period. The overall wind pattern will continue
to exhibit the typical diurnal tendencies with overall speeds aob
10 kts. There will likely be periods of light variability to even
calm conditions, especially during the diurnal transition.
Southerly winds are expected for a few hours mid to late morning
Wednesday at the Phoenix terminals before veering toward a W/SW
component. Breeziness will pick up around the region heading into
tomorrow afternoon with gusts to around 20 kts possible at times.

&&

.FIRE WEATHER...
Dry and tranquil weather conditions will persist through much of
the remainder of the workweek, with slightly above normal
temperatures. MinRH values each day will bottom out near 10%
areawide with poor to fair overnight recoveries. Fairly light and
diurnally driven winds are expected through at least Thursday,
with some afternoon upslope breeziness. Winds are likely to
increase by the end of the week into this weekend as an upper
level low pressure system moves into the western United States.
This may lead to locally elevated fire weather conditions,
particularly for the high terrain east of Phoenix during the
weekend, though temperatures will cool to slightly below normal.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$


DISCUSSION...RW
AVIATION...Smith/Lojero
FIRE WEATHER...Whittock

NWS PSR Office Area Forecast Discussion