638
FXUS65 KPSR 091750
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1050 AM MST Sun Jun 9 2024

.UPDATE...Updated 18z Aviation Discussion.

&&

.SYNOPSIS...
As a weak weather disturbance moves across the region today,
slightly cooler temperatures can be expected through Monday.
Temperatures will then heat up once again through the middle of
the upcoming week as high pressure builds over the area. Seasonably
dry conditions will prevail through the forecast period.

&&

.DISCUSSION...
The upper-level low that has been spinning for the past several days
near the Baja Peninsula is now finally approaching AZ and will
move through the state throughout the day. This feature will help
to keep 500 mb heights in between the 585-588dm range through
Monday, helping to slightly lower temperatures as highs across the
lower deserts will range between 102-106 degrees, which will be
near to slightly above normal levels for this time of the year.
Even though these temperatures are near to what is typical for
early to mid-June, it is still warm enough that the necessary heat
precautions should still be taken, especially when engaging in
outdoor activities.

Heading through the middle of the upcoming week, the overall
synoptic pattern will feature an upper-level low that will cutoff
off the coast of southern CA/Northern Baja Peninsula with a ridge
building downstream across eastern AZ through NM. 500 mb height
fields across the region from the building ridge will rise above
590dm, with the eastern half of AZ potentially seeing height fields
rising as high as 595dm late Wednesday through Thursday. This
will result in an uptick in temperatures beginning Tuesday and
persisting through Thursday, with another round of excessive heat
conditions likely, mainly across the lower deserts of south-
central AZ, as highs are forecast to reach 110+ degrees with areas
of major HeatRisk developing. Thus, an Excessive Heat Watch has
been issued for all of the lower deserts of south-central AZ as
well as for the San Carlos to Globe/Miami area in southern Gila
County from Tuesday morning through Thursday Evening. Even though
the greatest coverage of major HeatRisk is expected for mainly
Wednesday, high temperatures for Tuesday and Thursday are expected
to be not too different from Wednesday and thus it was decided to
include these days as well in the watch. Across the western
deserts, temperatures are expected to be a tad cooler due to the
closer proximity to the upper-level low and thus the HeatRisk is
expected to remain in the moderate category.

The ensembles are in good agreement in showing the aforementioned
upper-level low moving east northeastward from the southern CA
coastline through northern AZ on Friday, pushing the ridge axis
eastward into NM. As a result, 500 mb height fields will lower,
resulting in cooler temperatures closer to 105 degrees. The
increasing gradient between the ridge and the upper low will
cause in uptick in the afternoon breeziness Wednesday through
Friday.

Heading into next weekend, a large-scale trough is still forecast
to move through the Pacific northwest. There is still some spread
amongst the ensembles on the depth of this feature as it moves
eastward through the northern Great Basin and Intermountain West
Regions, however, the latest trend has been for a more shallower
trough which would allow for some flat ridging to build across the
Desert Southwest. This would result in a slight increase in
temperatures, with the latest NBM showing temperatures across the
lower deserts increasing close to 110 degrees once again.

&&

.AVIATION...Updated at 1750Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT;
No aviation weather concerns are anticipated through the TAF
period under SCT-BKN clouds mainly aoa 15 kft. Wind directions
will favor S/SE through the early afternoon before establishing a
more westerly component later in the afternoon, leading to a
prolonged period with a southerly cross runway component at KPHX
and KDVT over the next several hours. Wind speeds will mostly
remain aob 10 kt sustained, with some late afternoon and early
evening gusts up to 15-20 kt. Winds will favor more typical
diurnal tendencies this evening and going forward, with the E`rly
switch occurring sometime between 07-09Z, preceded by a period of
very light speeds and variability.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns are expected through the next 24
hours under FEW-SCT clouds mainly aoa 20 kft. SE winds at KIPL
will persist through the afternoon before veering out of the west
by the early evening. Gusts to around 20 kt will be possible at
KIPL during the evening. At KBLH, winds will maintain a southerly
component, gusting to around 20 kts this afternoon.

&&

.FIRE WEATHER...
Hot and seasonably dry conditions will continue to support a high
fire danger across the area into late next week. Slightly cooler
temperatures, although still remaining above normal, can be
expected through Monday before heating up once again heading into
the middle of next week. Winds will continue to generally favor
diurnal tendencies with occasional afternoon breeziness of 20-25
mph expected across most of the region. MinRHs ranging between
5-15% with poor to fair overnight recoveries of between 20-45%
will continue to be common during the next several days.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Watch from Tuesday morning through Thursday
     evening for AZZ534-537>555-559-560-562.

CA...None.
&&

$$

DISCUSSION...Lojero
AVIATION...Whittock
FIRE WEATHER...Lojero