475
FXUS65 KPSR 292112
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
212 PM MST Mon Apr 29 2024

.SYNOPSIS...
Warmer temperatures are anticipated over the next several days with
highs rising into the low to mid 90s across the lower deserts. An
upper level trough will pass through the Intermountain West mid-week
resulting in breezy conditions across the region. Otherwise, dry
conditions will prevail across the forecast area through at least
this weekend.

&&

.DISCUSSION...
Benign weather conditions persist as quasi-zonal flow prevails
across the Desert Southwest. Afternoon RAP analysis showed longwave
troughing over the central CONUS while a shortwave trough is seen
pushing into the Pacific Northwest. Locally, the quasi-zonal flow
pattern will support continued dry westerly flow aloft, promoting
mostly clear skies, while 500 mb heights continue to rise to around
575-578 dm today. Temperatures will respond accordingly as
afternoon highs warm up several degrees above normal in the lower
90s. Widespread Minor HeatRisk will continue. Similar
temperatures are in the forecast for tomorrow as the tranquil
weather pattern persists before slightly cooling Wednesday.

For the middle part of the week, a shortwave trough will swing
through the Intermountain West while the core remains removed to the
north from our area. However, we will see a tightening gradient as a
result of this shortwave with an associated weak frontal boundary
pushing into the region going into early Thursday. An increase in
breezy conditions is expected Wednesday/Thursday with gusts upwards
of 20-25 mph possible across much of the area. Temperatures for
Wednesday and Thursday will see some slight cooling while remaining
near to slightly above normal. Lower desert highs during this time
will top out in the low 90s.

Heading into this weekend, uncertainty remains high in regards to
the potential for a deeper trough to affect the western CONUS with
varying ensemble solutions with the pattern evolution. The GEFS
continues to favor a deeper, amplified trough diving south along the
West Coast this weekend before moving inland across California. This
solution would favor a cooler, breezier weather pattern for our
area. Meanwhile, the EPS, though the latest run of the ensemble has
trended toward a deeper trough, keeps the greatest negative height
anomalies further north across the Pacific Northwest. Depending on
how this pattern evolves will dictate the amount of cooling and
breeziness we see for the end of the week and into the beginning
of next week. For now, NBM deterministic temperatures for the
latter part of the week keep lower elevation highs in the low to
mid 90s, while the interquartile range displays a continued large
spread given the aforementioned uncertainties. Despite the
uncertainty in temperatures, ensembles and deterministic models do
agree that dry conditions are favored to persist through this
weekend and into early next week and thus PoPs remain nil.

&&

.AVIATION...Updated at 1120Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT and
Southeast California/Southwest Arizona including KIPL and KBLH:

Expect VFR conditions for all terminals. No major weather issues
anticipated through tonight under clear skies. Timing of the
usual diurnal wind shifts will be typical for this time of year
while any enhanced gusts remains minimal or absent. Look for
extended periods of nearly calm conditions during transition
periods.

&&

.FIRE WEATHER...
Warm and dry conditions will persist this week and into this weekend
with high temperatures around 3-5 degrees above normal each day.
Winds will be light and follow typical upslope/downvalley patterns
today and Tuesday before increased breeziness arrives Wednesday with
gusts reaching the 20-25 mph range across much of the area. Windy
conditions will also be possible across the western districts on
Thursday as a dry cold front passes through the Colorado River
Valley. Minimum relative humidity values will range from 8-15%
each day. Moisture recovery will range from poor to fair each
night, or around 25-50%.

&&

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

$$

DISCUSSION...Smith
AVIATION...Young/Trampp
FIRE WEATHER...Smith/Salerno