223
FXUS65 KPSR 120533
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1033 PM MST Tue Jun 11 2024

.UPDATE...Updated 06z Aviation Discussion.

&&

.SYNOPSIS...
High pressure will once again build over the Desert Southwest over
the next few days, pushing temperatures back to near, and for some
locations above, 110 degrees. In response, an Excessive Heat
Warning has been posted for south-central Arizona until Thursday.
A brief, relative cooldown will occur late in the week as an area
of low pressure moves over our forecast area.

&&

.DISCUSSION...
Current objective analysis reveals the Desert Southwest under the
influence of increasing heights aloft, while two areas of low
pressure flank the region to the east and west. Atmospheric heights
will continue their upward climb through the remainder of the day,
pushing near 589-592 dam across our forecast area. This will result
in an upward bump in temperatures, with high temperatures this
afternoon across the lower deserts ranging between 106-111 degrees.

Model guidance indicates further amplification of the upper-ridge
through Wednesday while the cut-off low to our west continues to
hover off the coast of northern Baja. Unseasonably high 500mb
heights of 592-594 dam (near the 90th percentile of climatological
normals) will promote another bump in temperatures for Wednesday
afternoon. NBM MaxT forecasts have highs ranging between 109-113
degrees, with Phoenix flirting with a record high (113 degrees set
in 2022). Widespread Moderate to locally Major HeatRisk will result
from these unseasonably hot temperatures and those planning to be
outside, or those who work outdoors, should take extra
precautions during the next several days. In response to this
period of heat, and Excessive Heat Warning has been posted for
today through Thursday.

The meandering area of low-pressure off the coast of Baja is
projected to move onshore by late Thursday, providing the region
with lowering heights aloft and increasing moisture levels. Relative
cooling will take place as a result of the falling heights, with
highs on Friday forecasted highs generally between 103-108 degrees
across the lower deserts. The increasing moisture ahead of the
low may yield some shower/thunderstorm activity across south-
central Arizona, with the best chances (currently 20-25%) focused
over high terrain locations north and east of Phoenix.
Additionally, breezy conditions will increase late in the week,
which combined with hot and dry weather will lead to enhanced fire
weather conditions.

Model clusters agree that once the aforementioned system ejects out
of the Desert Southwest, ridging will once again build in its wake.
Temperatures will likely near or exceed 110 degrees across much of
the lower elevations by Saturday. Anyone with outdoor weekend plans
should plan accordingly such as limiting time outdoors and
maintaining adequate cooling and hydration. Uncertainty increases
heading into the start of next week as a trough is shown pushing
into the Pacific Northwest. However, the general consensus amongst
models is that this troughing pattern will take hold across much of
the western CONUS, with the main uncertainty being how deep this
feature becomes. If the current forecast holds, a cooling trend can
be expected regardless, with how much things cool off being
dependent on how amplified this system becomes.

&&

.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...
Hot and seasonably dry conditions will continue to support a high
fire danger across the area through the week. Temperatures will
heat up over the next couple of days with afternoon highs across
the lower deserts approaching or exceeding 110 degrees through
Thursday. Winds will continue to generally favor diurnal
tendencies with occasional afternoon breeziness of 20-25 mph
expected across most of the region. MinRHs will range between
5-10% with overnight Max RHs between 15-35% expected. Going into
the end of the work week, a weather system is expected to traverse
the region and bring increasing breeziness, which will act to
promote elevated fire weather conditions. Additionally, the
weather system will bring a low chance (less than 10%) for dry
thunder to the high terrain east of Phoenix.

&&

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

CA...None.
&&

$$

DISCUSSION...Smith/RW
AVIATION...Young/95
FIRE WEATHER...Smith/Whittock