409
FXUS65 KPSR 212352
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
452 PM MST Fri Mar 21 2025

.UPDATE...Updated 00z Aviation Discussion...

&&

.SYNOPSIS...
The region will remain under the influence of high pressure well
into next week, leading to warming temperatures through early next
week and dry, tranquil conditions. The high pressure will reach peak
strength and encompass much of the Western United States by early
next week, resulting in afternoon highs warming well into the
nineties across the lower deserts and challenging daily records in
some places.

&&

.DISCUSSION...
Dry, tranquil weather conditions, with a gradual warming trend, will
continue into the weekend as the region remains under the influence
of flat upper level ridging. Dry quasi-zonal flow aloft will
continue to promote mostly clear skies and plenty of sunshine
through tomorrow and allow temperatures to continue to trend upward
into the weekend. Forecast highs warm into the mid to upper 80s
across the lower deserts Saturday, which is around 5-8 degrees
above seasonal normals. The warming trend stabilizes this weekend
as guidance show a weak disturbance propagating into the Desert
Southwest along the eastern periphery of a strengthening upper
level ridge over the eastern Pacific. We will see an increase in
high clouds Sunday as a result while 500 mb heights remain steady
around 575 dm. Afternoon highs Sunday will be similar to
Saturday`s, but thicker cloud cover may lead to some areas being
a degree or two cooler.

Ensemble guidance remain in excellent agreement that an unseasonably
strong upper level ridge will build across the Western CONUS Sunday
into Monday, resulting in temperatures warming up well above normal.
By Tuesday, guidance show 500 mb heights peaking around 582-584 dm,
or around the 97-99th climatological percentile, as the ridge axis
shifts over our area. Temperatures will respond, warming up well
above normal into the 90s early next week with daytime highs likely
peaking on Tuesday. Tying or breaking record highs will be possible
early next week, particularly on Monday and Tuesday. NBM
probabilities of tying/breaking record highs will be in excess of
80% Monday and in excess of 90% Tuesday. The latest NBM also
indicates up to a 40-60% chance of reaching 100 degrees on Tuesday
for the warmest lower desert locales. If Phoenix were to reach
100 degrees on Tuesday, it would be the earliest occurrence on
record, beating the current record (March 26, 1988) by a day.
Record warm lows will also be possible next week, particularly
Wednesday morning as urban areas could see lows near 70 degrees
due to thicker cloud cover.

A broad cut-off upper level trough is then forecast to form and push
into northern Mexico and southern portions of the Desert Southwest
Tuesday night into Wednesday. However, guidance doesn`t show it
allowing for much of a cooling trend Wednesday into Thursday. This
weak system won`t lead to significant height falls with global
ensembles indicating 500 mb heights falling to around 575-578 dm.
We will see a modest decrease in temperatures for the latter part
of next week with NBM highs dropping into the lower 90s Wednesday
and further cooling into the upper 80s to low 90s Thursday. By
late next week, uncertainty quickly increases in the evolution of
troughing over the eastern Pacific. The latest EPS continues to
indicate a more prominent shortwave trough swinging through the
Southwest CONUS next Friday, while the GEFS keeps the shortwave
energy well to our north, propagating it through the Pacific
Northwest. The greatest implication these diverging solutions will
have on the forecast will be uncertainty in temperatures late
next week as the NBM indicates ~10 degree spread in the
interquartile range by next Friday. Regardless of the differing
solutions presented by global ensembles, dry conditions are
favored to persist through at least the next week.

&&

.AVIATION...Updated at 2350Z.

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

No aviation weather concerns under mostly clear skies are expected
throughout the TAF period. The overall wind pattern will continue
to exhibit the typical diurnal tendencies with light speeds aob 8
kts. Extended periods of directional variability and nearly calm
conditions will be common, especially during diurnal transitions.

&&

.FIRE WEATHER...
Seasonably strong high pressure will persist across the region
through the weekend with the gradual warming trend and dry
conditions persisting. Lower desert high temperatures will warm into
the lower 80s across the lower deserts today and into the mid to
upper 80s over the weekend. Expect MinRHs mostly between 10-15% each
day with poor to fair overnight recoveries between 20-35%. Overall
light winds will continue through at least the weekend with
directions generally following typical diurnal patterns. Stronger
high pressure is forecast for the first half of next week leading to
lower desert highs climbing into at least the low to mid 90s.

&&

.CLIMATE...

Record high temperatures next week:

Date       Phoenix         Yuma        El Centro
----       -------         ----        ---------
Mar 24    94 in 1990    96 in 2008    93 in 1988
Mar 25    96 in 2022    99 in 1896    94 in 2022
Mar 26   100 in 1988    99 in 1988    98 in 1988
Mar 27    98 in 1986   100 in 1986    99 in 1988

&&

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

$$

DISCUSSION...Smith/Kuhlman
AVIATION...Lojero
FIRE WEATHER...Kuhlman
CLIMATE...Kuhlman