459
FXUS65 KPSR 311958
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1258 PM MST Fri May 31 2024


.SYNOPSIS...
Seasonably hot and dry weather conditions will persist
through early next week with temperatures running 3 to 5 degrees
above normal. By the middle through latter half of next week, high
pressure is forecast to strengthen across much of the western United
States, resulting in hotter temperatures as high get closer to 110
degrees across much of the lower deserts.

&&

.DISCUSSION...
A mostly quasi-zonal flow pattern is persisting across the Desert
Southwest as the region is entrenched between the subtropical ridge
located over central Mexico and cyclonic flow near the Canadian
border as well as the Pacific Northwest. This overall pattern is
expected to persist into early next week, with temperatures
remaining steady state with highs between 100-105 degrees across
the lower deserts, which is a good 3-5 degrees above normal for
this time of the year. This will continue to result in widespread
minor HeatRisk with pockets of moderate HeatRisk. A very weak
shortwave trough will bypass just to the north Sunday, however, it
will have no discernible sensible weather impacts other than
maybe slightly enhance the afternoon breeziness.

Heading into the Tuesday-Wednesday timeframe, the weather pattern
will be changing as a ridge of high pressure will amplify across
much of the western U.S while a weak upper-level low develops off
the Baja California Peninsula. In consequence, in response to the
amplifying ridge pattern, 500 mb height fields across the region
will be rising to between 588-594dm heading into the latter half
of next week. This will translate to hotter temperatures with
highs ranging between 105-110 degrees across the majority of the
lower deserts from next Wednesday through Friday. These hotter
temperatures will elevate the HeatRisk into the moderate category
across the majority of the area.

Even though there is high confidence of a strong ridge developing
across the majority of the western CONUS heading into the middle to
latter half of next week, the evolution of the aforementioned upper-
level low off the Baja Peninsula is a bit more uncertain as model
guidance differs in the overall positioning and whether or not
this feature will eventually move into our region. At this time,
GEFS seems to be the most aggressive in moving this upper low
into our region while both the Canadian and ECMWF ensembles are
not as aggressive. This overall evolution will determine whether
or not the region sees a slight cooling trend with highs in the
low to mid 100s or readings remaining near 110 degrees heading
into next weekend. This uncertainty is being reflected in the NBM
inter-quartile temperature distribution, which shows as high as
an 8 degree spread between the 25th and 75th percentile heading
into next weekend. With the upper-level low being positioned near
the Baja Peninsula, south to southeast flow along the east side of
the low will likely advect some moisture into the region late
next week through next weekend, just enough to cause an increase
in cloud cover and maybe some isolated weak afternoon convection
across the AZ high terrain.

&&

.AVIATION...Updated at 1710Z.

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

No major aviation concerns are expected across the region under
mostly clear skies. Winds will follow diurnal trends with speeds
generally aob 10 kts with occasional afternoon gusts ranging in
the mid-teens to around 20 kts. BLH will likely see slightly
higher speeds (10-12 kts) and more frequent gusts, but winds there
will begin to calm after sunset.

&&

.FIRE WEATHER...
Hot and dry conditions will persist into next week with lower
desert highs between 100 and 105 degrees, or 3-5 degrees above
average each day. MinRH values will continue to run between 5-10%
across the majority of the area each day, while overnight
recoveries will continue to range from poor to fair at around
25-40%. Winds will overall be fairly light following diurnal
tendencies with periodic afternoon gusts of 15-20 mph.

&&

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

$$

DISCUSSION...Lojero
AVIATION...RW
FIRE WEATHER...Kuhlman