872
FXUS65 KPSR 301727
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1027 AM MST Thu May 30 2024

.UPDATE...Updated 18z Aviation Discussion.

&&

.SYNOPSIS...
Dry and tranquil weather conditions will persist through at least
the weekend, but expect continued above normal temperatures as high
pressure generally dominates across the region. High temperatures
each day across the lower deserts will remain several degrees above
normal with readings between 100 and 106 degrees under sunny to
mostly sunny skies.

&&

.DISCUSSION...
Little change in the weather pattern through the weekend is
expected as our region continues to fall inbetween upper level
troughing across the northern U.S. and the sub-tropical ridge
positioned to the south. This will keep dry westerly flow in place
and H5 heights near climatological normals. The dry air mass will
also persist through at least the weekend with PWATs running
around 70-90% of normal resulting in continued clear to mostly
clear skies and low humidities. Temperatures will also remain
stable over the next several days with readings on average 3-5
degrees above normal. Most lower desert locations will see daily
highs reaching between 100-105 degrees into early next week.

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 the 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 prevail into next week with daily
highs remaining 3-5 degrees above normal. Overall light winds
will follow diurnal tendencies each day with afternoon gusts in
the mid-teens to around 20 mph. MinRH values will range between
5-10% each afternoon while overnight Max RHs range between 20-40%
for most places.

&&

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

$$

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