772
FXUS65 KPSR 011717
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1017 AM MST Tue Oct 1 2024

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
Persistent high pressure will continue to promote mostly dry and
abnormally hot conditions over the next several days, with afternoon
high temperatures nearing or exceeding record levels. Regional
moisture content may promote some virga and very isolated showers
this afternoon, especially around enhanced terrain features, but any
potential activity should result in little to no accumulations.

&&

.DISCUSSION...
The main talking point with the forecast will be the continuation of
unseasonably hot conditions as high pressure continues to encompass
the Desert Southwest. The hottest day of the next several looks to
be today as temperatures will range between 108 and 113 degrees
across the lower deserts, a good 15 degrees or so above normal for
this time of year. Phoenix Sky Harbor has already seen seven
consecutive days with a daily high temperature record either
being tied or exceeded, and this streak is unlikely to end today,
and may continue into next week. The high temperature forecast for
PHX this afternoon is 113 degrees, so today will likely become
the first October day ever with a temperature at or above 110
degrees since records began back in 1896. The Excessive Heat
Warning remains in effect until Friday evening for the Arizona
lower deserts and portions of southeast California, but it would
not be surprising to see this extended even further into the
upcoming weekend due to this unprecedented heat.

Although we will be dry in the lower-levels, regional moisture
profiles will actually be slightly above normal for this time of
year, which may support the development of some virga and very
isolated showers this afternoon. Most of the potential rainfall will
be focused around the high terrain of Gila and northern Maricopa
Counties, though it is not out of the question to see a separate
area of activity around the enhanced terrain of Pima and southern
Maricopa Counties as well. These latter areas will also have the
greater potential for an isolated thunderstorm due to better
atmospheric instability, as MLCAPE values will be near 250-500
J/kg. The main impact of this activity, even with the weakest of
showers, will be the some brief gusty winds exceeding 35 mph due
to the environment being supportive of potentially strong
downdrafts, with DCAPE values ranging between 1300-1900 J/kg. For
areas that find themselves under a relatively heavier shower/storm
a quick 0.10" is possible, but little to no accumulations are
expected otherwise.

&&

.AVIATION...Updated at 1715Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Easterly winds are expected to persist through the next 24 hours
with varying speeds. Speeds will be mostly be aob 10 kts. A few gusts
of 15-20 kts will occur this afternoon into early evening. We are
monitoring the potential for LLWS later this evening and overnight
as east winds increase just off the surface. Currently coming up
with magnitudes just shy of TAF LLWS thresholds. Otherwise, just a FEW
to SCT mid to high level clouds. There is a slight chance for
some virga to pass over Phoenix this evening, but odds of
VCSH/-SHRA are very low (<10%).

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation weather concerns with FEW to at times SCT mid
level clouds are expected through the TAF period. While light W to
N winds are expected at both terminals, extended periods of light
and variable winds will be common.

&&

.FIRE WEATHER...
Generally dry and abnormally hot conditions will continue through
this week as a strong area of high pressure sits overhead. Lower
desert high temperatures are expected to run between 103-113
degrees each afternoon. A slight chance (10-20%) of some very
isolated showers exists this afternoon across south-central
Arizona, with the majority of the activity being focused around
enhanced terrain features. Some showers may result brief periods
of gusty and erratic winds. MinRH values will run between 5-15%
each afternoon, while overnight MaxRH readings should range
between 25-35%, with some locally higher values across Yuma and
Imperial Counties. Outside of any shower activity this afternoon,
winds are expected to follow typical diurnal trends, with
occasional afternoon gusts near 20-25 mph.

&&

.CLIMATE...

Record highs this weekend and next week:

Date        Phoenix         Yuma         El Centro
----        -------         ----         ---------
Oct 1     107 in 2020    110 in 1980    110 in 1980
Oct 2     107 in 1980    112 in 1980    108 in 2020
Oct 3     105 in 2020    108 in 1952    108 in 1952
Oct 4     105 in 2020    109 in 1952    106 in 1952
Oct 5     105 in 2020    108 in 1917    106 in 2020
Oct 6     105 in 1917    108 in 1980    106 in 1964
Oct 7     104 in 1991    108 in 1987    105 in 1991
Oct 8     104 in 1987    107 in 1996    106 in 1996

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Friday for AZZ530>544-546-
     548>551-553>555-559.

CA...Excessive Heat Warning until 8 PM PDT Friday for CAZ562-566-567-
     569-570.

&&

$$

DISCUSSION...RW
AVIATION...Frieders
FIRE WEATHER...RW
CLIMATE...18