-- Discussion containing changed information from previous version are highlighted. --
499
FXUS65 KPSR 311710
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1010 AM MST Fri May 31 2024

.UPDATE...
-- Changed Discussion --
Updated 18z Aviation Discussion.
-- End Changed Discussion --

&&

.SYNOPSIS...
Seasonably hot and dry weather conditions are expected into early
next week with temperatures each day running 3 to 5 degrees above
normal. By the middle of next week, high pressure is forecast to
strengthen over the region leading to even hotter temperatures and
highs getting closer to 110 degrees for a good portion of the
lower deserts.

&&

.DISCUSSION...
The weather pattern continues to show weak and dry westerly flow
aloft across the Southwestern U.S. with any Pacific weather
systems only impacting the far northern U.S. into southern Canada.
The sub-tropical ridge also remains positioned well to our south
over Mexico allowing H5 heights over the Desert Southwest ranging
between 582-585dm, or right around normal for this time of year.
This pattern is expected to persist through at least Monday with
temperatures staying anywhere from 3-5 degrees above normal and
highs topping out mostly between 100-105 degrees.

By around next Tuesday, we will begin to see a shift in the upper
level pattern as a weak cyclonic circulation forms just to our
southwest, while stronger ridging forms over a good portion of
the Western U.S. Model ensembles are still uncertain how both
systems will evolve, including the strength and positions of both
the eventual cut-off low and the upper ridge. Since yesterday,
guidance has started to shift more toward having the cut-off low
initially tracking more to the southwest farther off the Baja
coast during the middle of next week. If this were to happen, it
would initially have no influence over our region allowing the
ridge and its projected 588-594dm H5 heights to fully impact the
region. So far this is what ensembles are heavily leaning toward
and it would lead to further warming and highs inching closer to
110 degrees from next Wednesday through Friday. The latest NBM
probabilities of seeing 110 degrees during this time are basically
unchanged at 20-30% for the typical warmest lower desert
locations, but given the potential heights later next week these
probabilities seem to be on the low side.

Even more model uncertainty is seen by next weekend as overall
guidance shows the cut-off low trying to swing back to the north
closer to or even into our region. If this were to occur it would
likely push temperatures down slightly, closer to 105 degrees.
Moisture levels are also seen increasing slightly across much of
the region later next week, but given we are essentially in our
climatologically driest part of the year it would take more than
just a little moisture to have any shot at rain. Likely the most
we could hope for is some higher level cloudiness and maybe a
stray afternoon shower or weak storm over the Arizona high
country.

&&

.AVIATION...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.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...Kuhlman
AVIATION...RW
FIRE WEATHER...Kuhlman