Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 270000
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
500 PM MST Tue Mar 26 2024

.UPDATE...00Z Aviation Discussion.

&&

.SYNOPSIS...
A weather system lingering across the region will
continue to result in below normal temperatures and bring chances
for showers and thunderstorms through this evening from Phoenix
and across the higher terrain areas to the north and east. From
mid to late week, high pressure will settle over the region
resulting in dry conditions and a strong warming trend. Another
stronger weather system will then bring more unsettled conditions
with increased rain chances and cooler temperatures from Sunday
into early next week.

&&

.DISCUSSION...
A longwave trough extending from the central Plains through the
western United States will continue to result in unsettled
conditions today. A subtle shortwave riding along the
western side of the trough resulted in scattered shower activity
across the higher terrain areas east of Phoenix during much of the
overnight into the early morning hours with another piece of
energy upstream expected to help spark additional convective
showers near the Mogollum Rim this afternoon. The northwesterly
flow aloft will then carry these showers southeastward affecting
mainly eastern Maricopa, Pinal and southern Gila Counties with
more isolated activity possibly making its way into the Phoenix
area. With the steep mid-level lapse rates still in place,
instability parameters are sufficient to spark thunderstorms as
well with the showers with CAPE values as high as 500 J/KG. Any
stronger storm will be capable of producing gusty winds in excess
of 30 mph as well as small hail. High temperatures today will
continue to once again remain well-below normal with highs only
topping out in the lower to mid 70s across the lower deserts.

The weather pattern shifts starting on Wednesday as the trough exits
to the east allowing a ridge of high pressure to build in, which
will persist through the end of the week. With the ridge settling
over the region, a drier air mass along with a strong warming trend
are expected. High temperatures on Wednesday will warm into the
upper 70s to low 80s across the lower deserts, with even warmer
readings Thursday through Saturday with highs in the low to mid
80s.

Attention will then turn to an upper-level low that is expected to
reach the Pacific Northwest coast Wednesday into Thursday and then
dive southward to be positioned off the California coast Friday into
Saturday. As the upper-level low dives southward off the California
Coast, it will be strengthening with 500 mb heights as low as 540dm,
which is near the climatological minimum for heights fields at
this level. Initially, the main hazard with this system will be
gusty winds starting on Friday but then peaking on Saturday as the
ECMWF EFI values rise to as high 0.6-0.8 across most of western
and central AZ, meaning the majority of the members are showing
highly anomalous winds for this time of the year. The other hazard
with this system will then be the rainfall potential. A strong
frontal band is likely to make its way from west to east across
the region between Saturday night through the day on Sunday
delivering moderate rainfall activity as well as isolated
thunderstorm activity as the low gradually moves eastward. By
early next week, as the cold core moves over Arizona, diurnally
induced showers and isolated thunderstorms will be likely,
especially across south-central AZ. Latest QPF amounts for the
entire event at this time range from 0.25-0.50" across the western
deserts to 0.50-0.75" across the lower deserts of south-central
AZ with amounts of over an inch across the higher terrain areas to
the north and east of Phoenix. Under the influence of the low,
temperatures will be on a cooling trend beginning on Sunday and
persisting through early next week with highs trending below
normal once again.

&&

.AVIATION...Updated at 2358Z.

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

Breezy westerly winds are expected until an outflow moves through
the PHX Metro from 0030Z-0130Z shifting winds to the NE with gusts
around 20-25 kt expected and occasional gusts around 30 kt.
VCTS/VCSH will also accompany the wind shift. After a couple hours
wind speeds will start to subside and maintain an easterly
component through tomorrow morning. Tomorrow afternoon winds are
anticipated to do their typical diurnal switch to the west with
speeds aob 6 kt. SCT-BKN clouds with bases aoa 6-8 kft are
expected through 02-03Z when clouds will start to lift and scatter
out with skies becoming clear late tonight through tomorrow
afternoon.

Southeast California/Southwest Arizona including KIPL and KBLH:

Breezy conditions at KIPL will be the main aviation concern
during the TAF period. Winds at IPL will follow diurnal trends
with gusts upwards of 25 kts this evening. At BLH, winds will
contain a W`rly component aob 10 kt before winds calm and become
more variable late tonight. Mostly clear skies can be expected
through tomorrow morning before FEW high clouds start to move in.

&&

.FIRE WEATHER...
Today will bring additional chances for mainly higher terrain
light showers and a few isolated afternoon thunderstorms before
high pressure settles over the region starting Wednesday. Winds
today will be breezy at times, particularly in the afternoon,
with gusts of 20-25 mph before diminishing into Wednesday. MinRHs
today will range from 15-20% over the western districts to 25-30%
over the lower deserts of south-central Arizona, and up to 50%
over the Arizona high terrain. Drier and warmer conditions
starting Wednesday will lower MinRHs across all of the lower
deserts into the teens to around 20% with day to day afternoon
breeziness persisting. Slightly above normal temperatures and dry
conditions are then expected to last into the early part of the
weekend before unsettled weather conditions move in by Sunday.

&&

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

$$

DISCUSSION...Lojero
AVIATION...Berislavich/RW
FIRE WEATHER...Kuhlman


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