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898
FXUS65 KPSR 110018
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
518 PM MST Fri May 10 2024

.UPDATE...
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Updated Aviation Discussion.
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&&

.SYNOPSIS...
A gradual warming trend is expected into the weekend
with above normal temperatures along with increasing chances of
triple digit highs across the lower deserts through next week.
Seasonably dry conditions along with afternoon breezes continuing to
result in areas of elevated fire weather conditions will persist
over the next several days.

&&

.DISCUSSION...
Latest water vapor satellite imagery depicts an upper-level low
pressure system situated across southern Nevada with an
anomalously strong upper-level high pressure system situated
across the Pacific Northwest. The low pressure system has been the
main culprit for maintaining temperatures slightly cooler than
normal the last several days. As the upper-level ridge axis
gradually shifts eastward during the next couple of days while on
a weakening phase, it will cause the upper-level low to also shift
eastward while also weakening in the process. As a result of the
gradual eastward shift of the low, upper-level height fields will
gradually be rising and thus temperatures will respond
accordingly. Temperatures today will be in the near normal range,
with highs across the lower deserts topping out in the low 90s
but then will warm up in the above normal range, into the middle
to upper 90s, heading through the weekend. There is an elevated
chance (>60%) that the western deserts may see highs approach the
triple digits by Sunday, whereas those elevated chances shift into
the south-central AZ lower deserts, including the Phoenix metro,
on Monday as the weakening ridge axis moves directly overhead.

With the westerly flow aloft in place due to the influence
of the upper-level low just to the north, afternoon breeziness will
continue through the weekend with gusts up to 20-25 mph, with the
strongest gusts expected on Saturday when the higher terrain areas
to the north and east of Phoenix are likely to occasionally gust
to near 30 mph. The gusty winds combined with the very dry air in
place will result in some elevated fire weather concerns.

The model guidance is showing a weak shortwave moving into the
Desert Southwest from the Pacific by the first half of next week.
This will cause a slight dip in the upper-level height fields and
as a result a slight cooldown in temperatures although likely
remaining above normal with highs generally in the mid to upper
90s across the lower deserts. There also seems to be some evidence
from model guidance that this trough will advect some higher
moisture into the region, with the potential of some afternoon
convection developing mainly across portions of the AZ High
Country by midweek.

Heading towards late next week into next weekend, ensembles show a
ridge gradually building into the Desert Southwest from the west
as the aforementioned trough shifts eastward. There is still some
uncertainty in the exact timing of when the ridge will build in as
some ensemble members hang on to the trough across the region slightly
longer. Nevertheless, with the upper-level height fields expected
to rise, temperatures will respond accordingly with highs likely
reaching the triple digits across the majority of the lower desert
communities heading into next weekend.

&&

.AVIATION...
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Updated at 0018Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:

Typical Spring diurnal wind patterns are favored through Saturday
at all terminals. Westerly gusts up to 15-20 kts this evening in
Phoenix should subside by 02-03Z and east winds will develop by
10-11Z. Wind gusts Saturday afternoon will pick up by 20-21Z and
be a bit stronger than today, peaking up to 20-25 kts, from the
west in Phoenix and north to northwest at KBLH. Wind will remain
light at KIPL. Skies will remain mostly clear, with FEW 12K ft
cumulus in Phoenix Saturday afternoon.
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&&

.FIRE WEATHER...
Temperatures are expected to warm over the next several days, with
chances for highs reaching 100 degrees increasing above 50%, at
least for the western districts, by late this weekend. Temperatures
are expected to remain above normal going into next week. MinRHs
will be in the 5-10% range across the lower deserts and in the
10-15% range across the higher terrain through this weekend, with
values slightly improving next week. Overnight recovery will be
poor in the 20-40% range through tonight, before improved
recoveries in the 30-60% range heading into early next week.
Typical springtime breeziness continues during the next several
days with afternoon and early evening wind gusts generally ranging
between 20-25 mph. These breezy conditions combined with dry fine
fuels, and low RHs will likely create some elevated fire weather
conditions. Dry conditions persist through next week.

&&

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

$$

DISCUSSION...Lojero
AVIATION...Benedict
FIRE WEATHER...Lojero/Young