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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS65 KPSR 211801
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1101 AM MST Sun Apr 21 2024

.Update...
-- Changed Discussion --
18z Aviation Discussion
-- End Changed Discussion --

&&

.SYNOPSIS...
Unseasonably warm temperatures with mostly sunny skies will persist
through the first half of the week. Today and Monday will be the
warmest days yielding widespread minor heat-related health risks.
The first of a series of weather systems is then expected to move
through the region late Wednesday into Thursday resulting in a
temperatures closer to normal while also supporting periods of
strong, gusty winds.

&&

.DISCUSSION...
Dry westerly flow continues to affect the Desert Southwest with a
shortwave ridge moving over the region today. This ridge will
boost heights aloft as well as temperatures with forecast highs in
the mid to upper 90s across the lower deserts. These very warm
temperatures will be the highest the region has seen so far this
spring and will be 10-12 degrees above seasonal normals. The H5
heights around 580dm will then last into Monday with very similar
temperatures to today`s readings with the only difference being
the introduction of breezy afternoon winds.

Monday will also see a Pacific trough begin to develop off the
West Coast, deepening on Tuesday as it slowly approaches
California. This trough will begin to impact our region starting
Tuesday as winds increase further with afternoon gusts commonly
reaching to around 25 mph in some areas. Heights aloft will also
begin to lower due to the approaching trough, lowering high
temperatures Tuesday a couple degrees. Ensemble guidance is now
consistent in showing the first shortwave trough moving ashore in
southern California midday Wednesday before tracking through
Arizona Wednesday night. This disturbance will contain little if
any moisture with only some high clouds out ahead of the main vort
max, but it will continue to bring breezy to possibly locally
windy conditions, especially during the afternoon/evening hours.
There should also be a noticeable drop in temperatures in the wake
of this dry system with highs back to or even a few degrees below
normal starting Thursday.

The weather pattern into next weekend and likely into the
following week will continue to support disturbances coming out of
the northwest and likely impacting the Desert Southwest. The
strongest shortwave trough still looks to move into the region at
some point between late Friday and Sunday with at least minimal
chances for precipitation over higher terrain areas. Temperatures
are also favored to cool down even further for next weekend with
the latest NBM forecast highs showing upper 70s and lower 80s
will be possible.

&&

.AVIATION...Updated at 1120Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation concerns are expected during the TAF period. Winds
will follow light and diurnal tendencies with periods of
variability between directional shifts. Other than a FEW passing
high clouds and mid-level cloudiness over the high terrain areas
to the north and east, skies will be mostly clear over terminal
locations through tonight.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns are expected during the TAF period. Winds
will be light and follow diurnal patterns. Other than a FEW
passing high clouds, skies should remain mostly clear through the
forecast window.

&&

.FIRE WEATHER...
Dry conditions with above normal temperatures will persist early
this week with winds becoming breezy as early as Monday, but more
so starting Tuesday. Min RHs will continue to fall into the 5-15%
range while overnight Max RHs mostly stay in a 25-45% range. A
cooling trend will occur during the latter half of the week
with a series of weather disturbances eventually bringing
temperatures back closer to the seasonal normal. Breezy to locally
windy conditions will also periodically impact districts with
afternoon gusts commonly reaching 20-30 mph through the rest of
the week. Humidity levels are likely to stay low, however should
exhibit some improvement late in the week with daily MinRHs only
falling into a 15-25% range. Given this combination of winds and
humidity levels, a periodic elevated fire danger should be planned
for during the second half of the week.

&&

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

$$

DISCUSSION...Kuhlman
AVIATION...Young/RW
FIRE WEATHER...18/Kuhlman