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761
FXUS65 KPSR 201018
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
318 AM MST Fri Sep 20 2024

.SYNOPSIS...
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A somewhat unsettled weather pattern will bring increasing rain
chances for mainly the northern portions of the region, with
continued breezy winds region-wide for today. Below normal
temperatures are expected the next couple of days before warming
and drying conditions will commence going into next week.
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&&

.DISCUSSION...
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Strong negative height anomalies continue to persist across
southern California, as the main circulation with the longwave
trough is nearing the L.A. area early this morning. Some shower
and thunderstorm activity has continued for portions of
California into the early morning hours, with noticeably dry air
in place over SE CA and into southwestern to southcentral AZ. This
drier air will limit shower and thunderstorm potential as the
strong dynamics with this trough would otherwise provide better
potential across the region. As such, the main activity is
expected to be limited primarily to areas of best dynamics as the
upper level low begins to migrate eastward, which looks to remain
along the northern fringes of the forecast area today and
tonight. The latest PoP outlook is around 30-40% for places such
as Joshua Tree NP for today, spreading eastward across La Paz,
Maricopa, and Gila Counties going into tonight. NBM probabilities
of any significant rain accumulations remain low, as the best
chances of a quarter inch or more totals are limited to Joshua
Tree NP at around 30-50%.

Aside from the rain potential, breezy winds will continue today,
more widespread across southcentral Arizona, with periodic
gustiness 20-30 mph during the afternoon and early evening hours.
Gusty winds look to continue further west as well across the
favored higher terrain areas and eventually into the lower deserts
of the Imperial Valley this evening. Otherwise, temperatures will
be noticeably cooler, as the main low center will migrate across
the region over the next couple of days. High temperatures should
run 5-10 degrees below normal during this period, with lower
desert lows in the mid-60s to low 70s for the next couple of
nights.

Heading into next week, the troughing feature will lift to the
northeast, with temperatures quickly rebounding back towards
normal as early as Sunday. High amplitude ridging is expected to
build across the Pacific Northwest, allowing some version of
troughing, with neutral to slightly negative height anomalies, to
persist across the region going into the middle of next week.
Ensemble clusters show some slight variance through Tuesday, but,
by Wednesday, the pattern looks to be such that the main ridge
axis will be more centered across the region, allowing temperatures
to reach several degrees above normal. There are some more
noticeable differences amongst the ensembles going into late next
week, as the next troughing feature sets up offshore of the West
Coast. However, general ridging looks to hang on across the
region during this period, resulting in continued above normal
temperatures and dry conditions.
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&&

.AVIATION...Updated at 0510Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
A diurnal wind pattern will continue to prevail through the TAF
period. Similar to today, there will likely an extended period of
southerly winds with SE-SW variability from the late morning
through at least the mid afternoon hours before eventually
switching out of the west to southwest. It may take till after
00-01z for winds at KPHX to completely switch out of the west.
Wind speeds will generally remain aob 10 kts, although occasional
gusts into the mid to upper teens will be likely during the
afternoon and early evening hours. FEW to SCT cumulus will be
common through the TAF period with varying bases between 6-10kft
AGL (lowest overnight and highest in the afternoon)

Southeast California/Southwest Arizona including KIPL and KBLH:
At KIPL, winds will prevail out of the west through the entire
period. At KBLH, winds will generally remain out of the south into
Friday afternoon before switching out of the west by late
afternoon. Elevated wind speeds are expected at KIPL, with gusts
upwards of 20-25 kts into Friday morning and once again by early
Friday evening. Lighter speeds aob 12 kts are expected at KBLH.
FEW-SCT cumulus will be common through the TAF period.

&&

.FIRE WEATHER...
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A drier and cooler airmass encompassing the region will result in
below normal temperatures through Saturday. Stronger southerly to
southwesterly will develop this afternoon, with gusts to 20-25
mph expected today, focused across higher terrain areas of the
western districts and southcentral AZ. MinRH`s will hover around
15-30% region-wide over the next couple of days, with some slight
drying first across the western districts starting Saturday and
spreading eastward on Sunday, with MinRH`s more in the 10-20%
range by the beginning of next week. Overnight RH recoveries will
be fair to good across the region over the next couple of
mornings, before degrading to generally fair to poor in spots
going into next week. Warming temperatures to above normal are
expected to develop late this weekend and persist through most of
next week.
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&&

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

$$

DISCUSSION...Young
AVIATION...Lojero
FIRE WEATHER...Young