197
FXUS65 KPSR 261733
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1033 AM MST Wed Jun 26 2024

.UPDATE...Updated 18z Aviation Discussion.

&&

.SYNOPSIS...
Today will mark a period of drying conditions across the region
with rain chances briefly ending, even over higher terrain areas,
by Friday. Above normal temperatures will persist through the rest
of the week with lower desert highs mainly ranging between 107
and 112 degrees. Monsoon moisture is expected to return late in
the weekend into early next week with chances for showers and
thunderstorms likely again affecting south-central and eastern
Arizona.

&&

.DISCUSSION...
Starting today, the synoptic weather pattern will become
increasingly less favorable for monsoon convection. A weak remnant
upper level disturbance is currently located just west of central
Baja, while the sub-tropical high is centered near El Paso. As the
remnant upper level wave tracks around the outer periphery of the
high through early Thursday it is forecast to move northward
through southern California. At the same time, the high center is
forecast to shift closer to our area, moving to just south of the
Arizona/Mexico border. This shift in the upper level pattern will
directly result in increasing southwesterly flow over nearly all
of our area already by this afternoon resulting in considerable
drying aloft, while subsidence aloft increases.

Despite still holding onto much of our boundary layer moisture
today, the combination of the increasing subsidence aloft and the
mid level drying should drastically lower rain chances across the
area. HREF guidance and the NBM PoPs generally only show minimal
(10-20%) chances for showers and thunderstorms over the higher
terrain this afternoon and evening with less than 10% chances over
the lower deserts. The drying will then persist through Thursday
and Friday with some of our boundary layer moisture getting
scoured out, particularly across the western deserts where surface
dew points are forecast to drop back into the 40s. Rain chances
will essentially come to an end starting Thursday with only slight
chances remaining over far eastern and northern Arizona. Friday
should be our driest day with PWATs falling back down to around
1.25" before moisture starts to increase once again over the
weekend.

Monsoon activity over Mexico is expected to increase Friday into
Saturday and this should yield increasing moisture into our area
as early as Saturday morning as the sub-tropical ridge begins to
shift to the east. Rain chances Saturday still look to be mainly
across southeast Arizona, but yet another tropical easterly wave
moving across northern Mexico this weekend is likely to turn at
least our mid level flow southeasterly by Sunday. Guidance then
favors moisture reaching much of southern Arizona starting Sunday
with PWATs back to between 1.4-1.7". The increased moisture along
with some potential weak influences of the remnant tropical wave
should bring back shower and thunderstorm chances to portions of
southern Arizona as early as Sunday. For now, guidance shows
decent monsoon moisture sticking around through much if not all of
next week across southern and central Arizona.

Forecast temperatures for the rest of the week and even through
early next week vary only a few degrees day to day. Above normal
temperatures of 3-5 degrees are expected nearly every day with
lower desert highs mostly topping out between 106-112 degrees
each day. Despite these readings falling into a Moderate HeatRisk
category, the heat will still be dangerous to those most
vulnerable and to those that underestimate the heat. The hottest
day is likely to fall on Sunday as the sub-tropical high
strengthens over the weekend, despite it already shifting
eastward away from the region. Forecast highs Sunday are currently
between 107-113 degrees across the south-central Arizona lower
deserts to 108-115 degrees across the western deserts. The latest
NBM forecast temperatures Sunday do present some localized areas
of Major HeatRisk, so Excessive Heat headlines may eventually be
needed for small portions of the area. Going through the first
half of next week, the increased moisture and monsoon activity
along with lowering heights aloft should allow for temperatures to
attempt to cool off closer to normal readings.

&&

.AVIATION...Updated at 1730Z.

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

No major aviation weather concerns expected through the TAF
period as the overall thunderstorm activity is likely to remain
well north and east of the terminals later today. There is a low
probability (10-20%) of an outflow from distant thunderstorms to
reach the terminals late this afternoon/early evening. Should it
occur, it will most likely come from the north. Otherwise, winds
should prevail out of the west through the evening and into at
least the first part of the overnight hours. Winds will likely
become light and variable early Thursday morning, with the best
for an easterly shift at KIWA. Wind speeds for the most part will
generally remain aob 12 kts, with a few gusts near 20 kts
possible during the afternoon and evening hours. Skies will
generally remain FEW-SCT, with the lowest cloud bases to around
10-12 kft.

Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation weather concerns expected through the TAF
period. Winds will follow their typical diurnal patterns, with
speeds generally aob 12 kt with the exception of some gusts near
20 kt in the afternoon and early evening, especially at KBLH.
Skies will remain mostly clear through the period with just a few
passing high clouds this evening.

&&

.FIRE WEATHER...
The weather pattern through the rest of the week will allow for
drying conditions and much lower chances for rain. Isolated
thunderstorm chances today are expected to be limited to the
higher terrain north and east of Phoenix before chances basically
come to an end starting Thursday. MinRHs will lower back into the
teens across the lower deserts by Thursday, while overnight
recoveries remain good at 35-50%. Winds will be fairly light today
with some periodic afternoon breeziness, before increasing more
on Thursday with afternoon gusts commonly reaching 20 mph. The dry
conditions with virtually no chances for rain should persist
through Saturday before moisture returns Sunday, increasing
humidities and potentially bringing back chances for
thunderstorms across south-central and eastern Arizona.
Temperatures through the period are expected to average several
degrees above normal.

&&

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

$$

DISCUSSION...Kuhlman
AVIATION...Lojero
FIRE WEATHER...Kuhlman