333
FXUS65 KPSR 191021
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
321 AM MST Thu Sep 19 2024

.SYNOPSIS...
Warming temperatures will continue today, prior to a brief cooling
trend going into the weekend. Temperatures will warm once again,
with lower desert highs exceeding 100 degrees, going into next
week. Dry conditions will persist, with some increased breeziness
developing across the region today and tomorrow. Otherwise, quiet
weather conditions continue through the middle of next week.

&&

.DISCUSSION...
Early morning satellite shows an enhanced mid-level moisture
plume cutting across southeastern Arizona, resulting in some
scattered clouds south and east of the forecast area. This
development is due to enhanced southwest flow as ridging across
central Mexico combines with the digging longwave trough currently
centered over the southern California coast. Negative height
anomalies will continue to persist over the Desert Southwest as
this trough continues to dig southeastward over the next couple of
days, resulting in temperatures at or below normal through
Saturday.

Winds will noticeably strengthen across the region over the next
couple of days, first across western Imperial County. As the
aforementioned trough continues to dig, stronger upper level winds
will traverse across southern California, with favored higher
terrain areas gusting 30-40 mph and portions of the Imperial
Valley gusting 20-30 mph this evening and tonight. Breezier winds
will then spread eastward tomorrow into southcentral Arizona, with
the most noticeable gustiness in the higher terrain areas of Gila
County of 20-30 mph. Wind impacts will be of lesser impact for
this system due to the deeper amplification of this trough,
pushing the strongest winds for this system into southern to
southeastern Arizona for tomorrow.

This trough will continue to progress eastward through Saturday,
with continued cooler temperatures. However, the mid-level weather
pattern will transition from troughing across the Desert Southwest
to a highly amplified ridging pattern, with the strongest height
anomalies setting up across the Pacific Northwest by early next
week. There remains discernible discrepancies on the progression
of the weakening trough and continued neutral to negative height
anomalies hanging on across the region going through early next
week. However, by mid-week, cluster analysis shows a pretty
consistent picture that the highly amplified ridge looks to be
more centered over the region. Thus, the main uncertainties in the
forecast at this point will be how quickly temperatures will warm
across the region, with latest forecast showing highs reaching
above 100 degrees once again no later than Monday, with continued
warming through mid-week, with lower desert highs of 100-105
degrees continuing into the latter portions of the week. Dry
conditions will persist, thus this warming trend will result in
above normal temperatures for most or all of next week.

&&

.AVIATION...Updated at 0500Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

No major aviation weather concerns are expected through the TAF
period. Wind directions will continue to exhibit the typical
diurnal tendencies, although an extended period of southerly winds
is anticipated starting late Thursday morning and persisting
through most of Thursday afternoon before eventually switching to
a westerly component most likely after the 23z-00z time frame.
Winds speeds will generally remain aob 10 kts. A FEW cumulus along
with a FEW-SCT cirrus decks are expected during the day on
Thursday.

Southeast California/Southwest Arizona including KIPL and KBLH:

Gusty sundowner winds developing at KIPL early Thursday evening
will be the weather issue through the TAF period. In the
meantime, winds during the overnight period will be very light and
variable before a more southerly component develops at KBLH by mid
to late morning and a southeasterly component develops at KIPL by
the early afternoon hours. Winds at KIPL will then eventually
switch out of the west by early Thursday evening, with speeds
picking up with gusts upwards of 20-25 kts. Wind speeds at KBLH
will generally remain light aob 10 kts. Mostly clear skies can be
expected throughout the period.

&&

.FIRE WEATHER...
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 and tomorrow. MinRH`s will hover around 15-25%
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.

&&

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

$$

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