941
FXUS65 KPSR 120839
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
139 AM MST Wed Jun 12 2024

.SYNOPSIS...
Very hot and dry conditions will continue over the next couple
days with the Excessive Heat Warning in effect through Thursday
across much of south-central Arizona and high temperatures
between 107 and 112 degrees across the lower deserts. A dry
weather system will then move across the area later Thursday into
early Friday potentially leading to some light showers across
higher terrain areas, mostly cloudy skies, and breezy conditions.
The coming weekend should see temperatures around 110 degrees
across the lower deserts before temperatures cool back to around
normal early next week.

&&

.DISCUSSION...
The sub-tropical ridge, which extends north to south from the
Great Basin into Mexico, is bringing H5 heights as high as 592dm
across the eastern half of Arizona. Lower heights down to around
588dm are seen across the western deserts through southern
California as it remains in closer proximity to a cut-off low that
has been nearly stationary west of Baja. For today and Thursday,
this set-up will again bring very hot temperatures across the
majority of the area with highs between 106-110 degrees across
southeast California to 108-112 degrees across the south-central
Arizona lower deserts. An Excessive Heat Warning remains in effect
through Thursday for Maricopa, Pinal, and portions of Gila County
as these temperatures represent a Major HeatRisk for portions of
the counties.

During the daytime hours Thursday, guidance shows the cut-off low
beginning to track northeastward closer to southern California
before moving through southern California into western Arizona
Thursday night. Southerly flow is forecast to increase on Thursday
into Arizona leading to some increased moisture advection in the
mid to upper levels. Model soundings show this moisture layer down
to around 13-15K feet by Thursday afternoon which should be
enough to lead to some high-based shower activity across southern
and central Arizona Thursday afternoon and evening. Given the very
dry air below the cloud bases, the most the lower deserts can
expect is some sprinkles, but some very light measurable rainfall
with PoPs of 10-20% will be possible over the Arizona higher
terrain. Also can`t completely rule out some localized gusty winds
mainly across western Arizona due to these possible virga
showers.

The cut-off low will continue to weaken and move into northern
Arizona on Friday while the rebuilding sub-tropical ridge moves in
behind from the southwest. Forecast temperatures are a few degrees
cooler across Arizona on Friday due to the low, but the building
heights across the western deserts should lead to highs around 110
degrees across southeast California and far southwest Arizona. As
H5 heights once again rise to between 590-592dm Friday night into
Saturday, temperatures will heat up further on Saturday as NBM
forecast highs are mostly between 109-114 degrees. These
temperatures will once again flirt with Major HeatRisk in some
areas.

Starting Sunday, ensemble guidance heavily favors a fairly strong
upper level trough digging across the Northwest U.S. with the
southern fringes of the troughing extending as far south as the
Desert Southwest. This will begin to lower heights across our
region, but the cooling will be subtle on Sunday before becoming
much more noticeable by Monday. The core of the trough is expected
to miss us to the north as it likely moves through the Great
Basin on Tuesday, but it is expected to bring some modest relief
from these very hot temperatures. NBM forecast temperatures lower
back to around normal for the first half of next week with lower
desert highs mostly between 102-107 degrees.

&&

.AVIATION...Updated at 0535Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT;
VFR conditions at all terminals under some passing high clouds
can be expected through the TAF period. Winds will continue to
exhibit diurnal tendencies with speeds generally remaining aob 10
kts, although some occasional afternoon/early evening gusts into
the mid-teens cannot be ruled out. Winds will again have
tendencies to have variability characteristics in direction and
speeds during the transition periods, especially at KPHX.

Southeast California/Southwest Arizona including KIPL and KBLH:
VFR conditions at both terminals under some passing high clouds
can be expected through the TAF period. At KIPL, winds will be out
of the westerly direction into the overnight hours before light
winds settle in into the morning hours. At KBLH, winds will
generally be out of the south to southwest. Wind speeds will
remain aob 10 kts through tomorrow morning, with afternoon winds
generally around 10 kts, but cannot rule out sustains reaching up
to 15 kts, with occasional gusts above 20 kts at both terminals in
the later portions of the afternoon and into the evening hours
tomorrow.

&&

.FIRE WEATHER...
Well-above-normal temperatures along with dry conditions will
prevail over the next couple days. Lower desert high temperatures
will top out between 107-112 degrees through Thursday. Winds will
continue to favor diurnal tendencies with occasional afternoon
gusts up to 20 mph today and to around 25 mph on Thursday when
some high based virga shower activity could bring a brief
enhancement of the winds. MinRH values will range between 5-10%,
while poor overnight recoveries can be expected with MaxRHs only
reaching towards 15-35%. Above normal temperatures will continue
through the upcoming weekend, while winds increase further with
afternoon gusts of 20-30 mph likely. The combination of the
increased winds and continued low RHs will create even higher
fire danger across the area this weekend.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Thursday for AZZ534-
     537>555-559-560-562.

CA...None.
&&

$$

DISCUSSION...Kuhlman
AVIATION...Young/95
FIRE WEATHER...Kuhlman