174
FXUS65 KPSR 140529
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1029 PM MST Sun Apr 13 2025

.UPDATE...Updated 06z Aviation Discussion.

&&

.SYNOPSIS...
High pressure aloft is still present over the region but has relaxed
enough to avoid triple digit temperatures for this afternoon by a
few degrees. This is due to a series of incoming weather systems
that started to lead to a slight cooling trend. However temperatures
will remain above normal through the middle of next week. This
afternoon Fire weather remains a concern in the higher terrains due
to increased wind speeds, and dry conditions.

&&

.DISCUSSION...
WV imagery shows a troughing feature bringing upper level moisture
into the region contributing to the SCT-BKN cirrus cloud coverage in
the eastern half of the region. The increase in cloud coverage is
expected to remain for most of today through tuesday morning and in
conjunction with lower 500mb heights the slight cooling trend will
extend to the middle part of next week, but still running 5-10
degrees above normal (upper 80s to low 90s).

Models are beginning to see slightly better agreement in the
troughing system off the coast of southern CA moving eastward by
late next week. From that system a short wave looks to break off
early and move towards the southwestern portions of the region by
Monday night into Tuesday morning. This will bring an increase in
moisture into these areas. Unfortunately, the bulk of this moisture
will remain in the mid levels over a very dry lower level, resulting
in poor chances of seeing any measurable rainfall, with virga to
light showers being the most possible outcome.

Once these (at most) light showers move to the north out of the
region, Tuesday night, clear skies are expected to return through
Thursday. Although there is growing agreement in the models,
uncertainty still remains for the later half of next week into next
weekend in the strength of the trough in the Eastern Pacific. A more
pronounced cooling trend will be felt near the end of the work week
into the weekend, but again with the uncertainty NBM interquartile
temperature spreads continue to have around a 10 degree difference.
A more progressive pattern would result in some cooler (near normal)
temperatures, while a more amplified pattern would result in much
cooler (below to considerably below normal) temperatures as well as
increasing precipitation chances as early as Friday and extending
through the weekend depending on how long this trough may linger
across the Desert Southwest. Current NBM POPs peak Friday night into
Saturday with chances between 25-35% across the higher terrain areas
north and east of Phoenix and between 10-20% across the lower
deserts. More monitoring will be needed throughout the week to see
how models evolve with this potential significant pattern change.

&&

.AVIATION...Updated at 0530Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The primary aviation concern through the forecast period will be
lower than usual confidence in wind directions Monday afternoon
and evening, under SCT-BKN and occasionally OVC cloud decks mostly
AOA 15 kft AGL. Winds will complete their shift to the typical
E/SE directions over the next few hours. By late Monday
morning/early afternoon, direction will tend to veer from SSE to
SW, though confidence is low that a predominant westerly component
will take hold at KPHX until the evening. Instead, a period of
southerly variability may prevail across the terminals during the
afternoon. Scattered virga showers will be present across the
region Monday afternoon and evening, which could cause briefly
erratic winds as they pass overhead.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation concerns will exist through the TAF period under
SCT-BKN and occasionally OVC cloud decks AOA 15 kft AGL. Winds
will follow typical diurnal tendencies at both terminals, with
directions favoring WSW this evening and overnight at KIPL before
shifting SE early Monday morning. Winds at KBLH will vary from SW
to SSE through the period, with an extended period of light speeds
and variability Monday morning. Speeds will generally remain AOB
12 kts sustained, though occasional gusts into the upper teens
seem likely at KBLH Monday afternoon into the evening and at KIPL
Monday evening.


&&

.FIRE WEATHER...
The Red Flag Warning that was issued for the higher terrain of
South Central Arizona has been allowed to expire, as winds have
relaxed below criteria early this evening. Overall lighter winds
will prevail early this week, however, afternoon breezes to 15-20
mph can be anticipated, as is typical for this time of year. As a
weak weather disturbance passes over the region Monday night,
expect temperatures to cool a few degrees from Monday to Tuesday,
resulting in slight improvements in afternoon MinRHs from the
single digits into the teens. Overnight recoveries will increase
from their values tonight (upper teens to 35%) to around 25-45%
Monday night. Seasonably warm conditions will persist through the
middle of the week, with locally elevated fire weather concerns
returning by Wednesday as winds increase ahead of an approaching
weather system.

&&

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

$$

DISCUSSION...Ryan
AVIATION...Whittock
FIRE WEATHER...Whittock/Ryan