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000
FXUS65 KPSR 110514
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1014 PM MST Wed Apr 10 2024

.UPDATE...Updated 06Z Aviation Discussion.

&&

.SYNOPSIS...
High pressure will be the dominant feature over the region during
the next few days, allowing temperatures to warm to their highest
values so far this year with nineties forecasted across the lower
deserts for Thursday and Friday. A weak system will brush our area
Friday bringing widespread breezy conditions before a more potent
system approaches the Desert Southwest that will help cool
temperatures to below-normal levels by the end of the weekend.

&&

.DISCUSSION...
High pressure has continued to build over the western CONUS over the
past 24 hours and will be the dominant feature over the Desert
Southwest over the next few days. Temperatures will continue their
upward trend as highs this afternoon will be 3-6 degrees warmer
compared to yesterday, with some locations, especially in the
western deserts of SE California and SW Arizona, seeing their first
90F readings so far this year. The Phoenix area will likely have to
wait another day to see its first 90F (occurs March 30th on average)
as NBM probabilities only give parts of the metro a 10-20% chance of
reaching that mark. Much of the region can expected to see some of
the warmest temperatures since last Fall on Thursday as forecasted
highs call for widespread lower to middle 90s across the lower
deserts, though a few readings in the upper 90s, primarily for areas
located in and around the Imperial Valley, cannot be completely
ruled out.

Global ensembles continue to pick up on a very weak and dry trough
approaching the Baja Peninsula on Friday. This feature is not likely
to move on-shore as forecast trends have it merging with a much more
potent low diving south across the far eastern Pacific. The most
sensible impact of this end-of-the-week system will be the return of
region-wide breezy to windy conditions. The most enhanced winds will
focus over much of SW Arizona and typically breezy areas of SE
California, with the NBM mean values showing peak gusts of 40-45
mph. However, as mentioned in the previous discussion, these values
may be a bit overdone as 850mb guidance from global ensembles shows
peak flow at this level between 20-30 kts. In this case, it would
be reasonable to expect peak gusts between 25-35 mph Friday
afternoon, with some locally higher gusts. There is a signal
pointing to the development of a 35-45 kt low-level jet over far
SW Arizona late Friday/early Saturday, but it may develop outside
the timeframe for best mixing, limiting higher surface gusts over
this region. Temperatures Friday afternoon are anticipated to drop
slightly but should remain well above normal, with forecasted
highs continuing to run in the lower to middle 90s.

The aforementioned more potent low will move along the California
Coast this weekend before eventually moving inland by Sunday. Some
uncertainty remains regarding how this system will evolve and how
far south it will track as model guidance has now brought the center
of the low further north compared to what was observed 24 hours ago
though the base of the trough is still expected to move across the
Desert Southwest. Regardless of how far the center of this low
tracks, cooler air will spread across the region, leading
temperatures on a cooling trend towards below normal levels through
Monday. Many areas may not see afternoon highs get out of the 70s on
both Sunday and Monday. Regional pressure gradient enhancement is
also anticipated as this system approaches, likely resulting in a
continuation of breezy to locally windy conditions through as far as
Monday for some areas before the trough ejects eastward by Tuesday.
With a more northerly track now being favored, moisture fetch over
the region will be lacking, yielding almost no rain chances during
this system`s residence over our forecast area.

&&

.AVIATION...Updated at 0520Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major aviation weather concerns are anticipated through the TAF
period under clear skies. Winds will remain light (aob 8 kts
sustained) and generally follow their diurnal tendencies. However,
E winds will gradually veer SE-SSE late tomorrow morning and into
the early afternoon (18-21Z), eventually switching SSW-SW by late
afternoon (23-01Z). Directions will continue to veer over the
early evening hours, potentially going light NW-N or very light
and VRB as the surface decouples. The typical E`rly drainage
winds establish between 04-07Z tomorrow evening. Beyond the
current TAF period, the next aviation concern will be focused on
gusty southwest winds during the day on Friday.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns are expected over the next 24 hours
under clear skies. Winds will remain light (aob 6 kts sustained)
and favor W at IPL and NW at BLH overnight. Beginning tomorrow
morning, confidence is low in wind directions. Height falls to the
west from an approaching low pressure system could lead to a
prevailing E`rly component through much of the daytime hours, but
extended periods of variability will be common at both terminals.


&&

.FIRE WEATHER...
Dry conditions and warming temperatures will prevail over the
next few days as strong high pressure builds over the region.
Today and Thursday, winds will be fairly light, 5-15 mph, across
all districts, with directions following typical diurnal trends
and terrain influences. The environment will be quite dry through
the remainder of the week, as temperatures also warm to the
hottest (90s) they have been so far this year. Minimum afternoon
RHs will fall below 15% each day with limited overnight recover
(up to 30-40% RHs). A weak disturbance Friday will lead to
widespread breezy conditions, especially during the afternoon and
evening. Winds will be strongest in Southwest AZ with gusts
pushing as high as 35-40 mph. Most areas will see peak southerly
gusts up to 25-35 mph. Another system this weekend, passing mainly
to the north, will lead to continued daytime breeziness, bring
cooler temperatures, and increase RH values slightly. These breezy
conditions, especially Friday, could lead to elevated fire
weather conditions where there are any dry fine fuels.

&&

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

$$

DISCUSSION...RW
AVIATION...Whittock
FIRE WEATHER...Benedict