000
FXUS65 KPSR 231122
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
422 AM MST Tue Apr 23 2024


.UPDATE...Updated 12z Aviation Discussion...

&&

.SYNOPSIS...
Noticeable cooling will take place through the remainder of the
week as an area of low pressure works its way off the eastern
Pacific towards the Desert Southwest. A more potent trailing
system will help to keep temperatures cooler than normal through
at least the start of this weekend. These disturbances will help
generate breezy to locally windy conditions across the region over
the next several days, while the secondary system helps to
increase rain chances, albeit slightly, on Saturday.

&&

.DISCUSSION...
Current upper-air analysis reveals low-amplitude ridging
encompassing much of the western CONUS which has helped push
temperatures to well-above normal levels across the Desert Southwest
for the past several days. This pattern will continue for at least
one more day or so, helping to keep todays afternoon highs
unseasonably hot across the region, though not as hot as the past
few days due to a slight decrease in temperatures aloft.
Afternoon temperatures across lower deserts of south-central
Arizona will still be a good 10 degrees above normal for this time
of year, but it is unlikely (<10%) that triple digit heat is seen
as temperatures should generally range in the middle 90s. A
similar drop in day-to-day temperatures should be observed across
the western deserts with daytime highs forecasted in the lower to
middle 90s.

A weak area of low pressure will approach the coast of Southern
California and northern Baja over the next few days, helping to
flip our pattern from hot and tranquil to "cooler" and more
unsettled. The initial influence of this trough will be felt
across parts of southeastern California this evening as breezy to
locally windy conditions develop due to a tightening of the
regional pressure gradient. Winds speeds are likely to remain
below advisory level criteria (40+ mph gusts), but occasional
gusts exceeding 40 mph cannot be completely ruled out across far
western Imperial County. Similar conditions will redevelop
Wednesday afternoon, this time with greater coverage across
southeastern California, as the aforementioned system continues to
push closer to our forecast area. Gusts 25-35 mph will be common
across Riverside and Imperial Counties, with areas in and around
the Imperial Valley and Salton Sea likely (>70% chance) experiencing
advisory level gusts. Enhanced breeziness will then spread
further east across southwestern and south-central Arizona by
Thursday as this trough traverses the region.

The other noticeable impact of this shortwave will be
the noticeably cooler temperatures as we head into the mid and
latter part of the week. Negative height anomalies will begin to
spread over the Desert Southwest by late Wednesday/early Thursday,
helping to kick off a rather quick cooling trend with day-to-day
lower desert temperatures falling from the upper 80s to lower 90s
Wednesday, to the lower and middle 80s by Thursday. Forecasted highs
for Friday will be similar to those on Thursday, with continued
lower to middle 80s forecasted across lower-elevation communities.

Global ensembles continue to show a secondary, but more potent
low, approaching the southwestern CONUS by late Friday/early
Saturday, which is likely to help keep breezy and cooler than
normal conditions in the forecast through at least the start of
this weekend. With the expectation that this trailing system will
be deeper compared to the low during the workweek, greater
regional moisture flux should be realized which may result in
increased rain chances by Saturday, mainly for south-central
Arizona. However, models at this time are not very bullish on rain
chances for our forecast area, with the highest odds only being
around 20% for the enhanced terrain areas of Maricopa and Gila
Counties.

&&

.AVIATION...Updated at 1120Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major aviation weather concerns under mostly clear skies are
expected through the forecast period. Winds will follow diurnal
tendencies, however, a several hour period of southerly crosswinds
can be expected after 16-17Z with speeds of around 10 kts.
Eventually by the mid to late afternoon hours, winds will switch
out of a more predominant westerly direction with occasional gusts
in the mid to upper teens before subsiding by the mid to late
evening hours.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation weather concerns under clear skies are expected
through the forecast period. Winds will follow diurnal tendencies
with elevated gusts up to 20-25 kts expected in the afternoon at
KBLH and in the late afternoon through evening hours at KIPL.

&&

.FIRE WEATHER...
Above-normal temperatures will continue for the next few days
before a noticeable cooldown takes place over the latter portion
of the week. Breezy to locally windy conditions will be common
across the region over the next several days as a result of an
approaching low-pressure system. This enhanced breeziness may
result in periods of elevated fire danger, especially for the
western districts, through Wednesday. Fire danger should
decrease as RH values improve through the remainder of the week,
with MinRHs rising from 10-15% today and Wednesday, to 15-25% by
Thursday. Overnight recoveries will follow a similar trend with
values rising to 40-70% by Wednesday night/Thursday morning.

&&

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

$$

DISCUSSION...RW
AVIATION...Lojero
FIRE WEATHER...RW