233
FXUS65 KPSR 302059
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
159 PM MST Thu May 30 2024

.SYNOPSIS...
Expect high temperatures to remain above normal through the rest
of the work week, into the weekend, and into next week.

&&

.DISCUSSION...
The hot, dry, and clear skies weather pattern persists across the
Southwest as dry zonal flow prevails with upper ridging now
shifting east across the central CONUS. Ensemble guidance
indicates 500 mb heights will remain steady around 583-585 dm
through the remainder of this week and into the start of next
week. This will keep afternoon temperatures each day several
degrees (3-5) above normal as lower desert highs top out in the
100-106 degree range for most places. With these temperatures will
come widespread Minor and pockets of Moderate HeatRisk, so the
necessary heat safety precautions should be exercised. Winds
through the rest of the work week will overall remain light,
outside of periodic afternoon wind gusts to around 20 mph. A very
weak shortwave pushing through the Southwest this weekend may
slightly enhance winds and also lead to a degree or two dip in
temperatures.

By next Monday and Tuesday, guidance continues to favor a weak
cyclonic circulation forming just off the southern California
and northern Baja coast. Eventually, this feature is likely to
become fully or partially cut off from the main flow during the
middle part of next week as it should strengthen a bit more and
wobbles just to our west for several days. For now, guidance
highly favors this disturbance staying over the Pacific or at most
reaching into portions of southern California later next week,
but either way it should have little impact on our sensible
weather conditions. Moisture levels are likely to increase across
the Southwestern U.S. next week, but much of the moisture will
stay to our west and north leaving near to slightly above normal
PWATs for our area. As of now, the most we can hope for is some
higher level cloudiness and maybe some low end rain chances across
the Arizona high country at some point late next week into the
following weekend.

The main forecast concern is the potential for even hotter
temperatures during the latter half of next week as the sub-
tropical ridge currently to our south is expected to strengthen
and shift northward through the Southern Plains and likely
northwestward through much of the Desert Southwest into the Great
Basin by around next Wednesday. Both the GEFS and EPS mean H5
heights are shown increasing to between 588-594dm over at least
much of Arizona and New Mexico during the middle of next week.
Model guidance is nearly certain of this ridge building over our
region, but there are still differences on how strong it will be
and how far west it can build due to the expected presence of the
cut-off low. For now, guidance is definitely leaning toward hotter
temperatures by next Wednesday through the rest of next week with
the latest NBM forecast highs between 105-109 degrees over much
of the lower deserts. If the cut-off low ends up closer to our
region, temperatures are not expected to be that hot, but so far
that is the less likely solution. Starting next Wednesday, the NBM
shows up to a 20-30% probability of reaching 110 degrees for the
warmest lower desert locations. Hot temperatures of this magnitude
are not unusual for the first week of June as daily records for
Phoenix range from 111-115 degrees and records for Yuma and El
Centro are a degree or two higher. As temperatures reach near 110
degrees, this would put the majority of the area well within a
Moderate HeatRisk.

&&

.AVIATION...Updated at 1730Z.

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

No aviation weather concerns will exist through the TAF period
under mostly clear skies and at times FEW high clouds aoa 20 kft
later in the period. Winds will favor light and diurnal tendencies
across the Phoenix area terminals, with periods of variability
preceding directions switches and occasional westerly gusts this
afternoon into the teens. For the SE California terminals, SE
winds will be favored through the afternoon at KIPL before turning
W this evening, and S to SW winds will be favored through the
period at KBLH. Overall, very similar wind patterns to the last 24
hours are expected across all sites.

&&

.FIRE WEATHER...
Hot and dry conditions will persist through the remainder of this
week with daily highs remaining 3-5 degrees above average.
Daily highs will reach the 105 mark in most lower desert
locations with widespread readings between 100-108 persisting
through the remainder of the week into the weekend. MinRH values
will be 10% or less across the central and western deserts each
afternoon and overnight recoveries will continue to range from
poor to fair at around 25-40%. Winds are expected to generally
remain below 15 mph.

&&

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

$$

DISCUSSION...95/Kuhlman
AVIATION...Whittock/Frieders
FIRE WEATHER...95