339
FXUS65 KPSR 221152
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
452 AM MST Sun Sep 22 2024

.UPDATE...Updated 12z Aviation Discussion.

&&

.SYNOPSIS...
Temperatures will steadily warm over the next few days reaching
into an above normal category as strong high pressure builds over
the region. Dry air will also remain entrenched over the area
yielding little to no chance for precipitation through the
entirety of the coming week.

&&

.DISCUSSION...
The taste of fall weather looks to be short-lived as the last of
the low pressure systems that brought the cooler weather is
quickly moving northeastward away from the region. Upper level
troughing will still stick around for today, but heights aloft
will quickly rise, as well as temperatures. Highs today are
expected to reach into the normal range and this will be the last
day for a while that sees temperatures near normal.

A strong upper level ridge currently building off the northwest
Pacific coast will shift inland over the Pacific Northwest on
Monday and then shift east southeastward over all of the Interior
West by Tuesday. This ridge will become our dominant weather
feature across the Desert Southwest starting Tuesday and likely
through the rest of the week. Ensemble mean H5 heights are seen
rising to around 588dm over our region on Tuesday with very little
fluctuations in the heights aloft through the rest of the week as
this develops into an Omega Block pattern. Model runs over the
past several days have been trending a few degrees warmer,
especially later in the week with forecast highs now peaking right
around record temperatures starting Wednesday in Phoenix to a few
degrees shy of record in Yuma and El Centro. Forecast highs
should begin to top 100 degrees over the majority of the lower
deserts starting Monday with further warming through mid week. By
Wednesday, highs are likely to top out between 103-107 degrees
across the lower deserts with overnight lows creeping into the mid
70s on average. Expansive areas of Moderate HeatRisk are expected
to develop by Wednesday with patchy areas of Major HeatRisk
possibly on Thursday and Friday as NBM forecast highs peak between
104-108 degrees.

By next weekend, model spread increases considerably with some
members attempting to push the ridge farther to the east into the
Southern Plains while allowing a near cut-off low to move into
western portions of the Desert Southwest. Overall, a majority of
members still keep the ridge mostly over our region through next
weekend resulting in continued above normal temperatures. The
influence of the potential cut-off low may end up bringing some
slight cooling by next weekend and this is reflected in the NBM
forecast highs dropping roughly five degrees over the western
deserts to 2-3 degrees across the south-central Arizona lower
deserts. No matter how the pattern evolves later this week into
the weekend, dry conditions will continue to prevail.

&&

.AVIATION...Updated at 1200Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation weather concerns are expected through the TAF period
as dry, tranquil conditions prevail. Light, diurnal tendencies aob
8 kts will continue through the period with winds becoming light
and variable at times during transition periods. Mostly clear
skies will continue with mid clouds generally remaining across the
high terrain north and east of Phoenix Sunday afternoon.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns are expected through the next 24
hours. Light and variable winds less than 7 kts will be prevalent
at both terminals through the period. Clear skies will persist.

&&

.FIRE WEATHER...
High pressure will gradually build over the region early this week
resulting in warmer temperatures and dry conditions. Above normal
temperatures with lower desert highs topping 100 degrees are
expected starting Monday. MinRHs will fall from 10-15% over the
lower deserts today to 8-12% starting Monday with higher terrain
areas seeing up to 20%. Expect a more traditional diurnal wind
pattern across the region over the next several days with little
to no breeziness. Much of the same is expected through the rest of
the week as the high pressure system keeps above normal
temperatures and dry conditions over the region.

&&

.CLIMATE...

Record highs next week:

Date        Phoenix         Yuma         El Centro
----        -------         ----         ---------
Sep 25    108 in 1989    112 in 1963    110 in 2015
Sep 26    108 in 1989    111 in 2010    110 in 2010
Sep 27    107 in 2009    111 in 1963    111 in 2009
Sep 28    108 in 1992    108 in 1994    109 in 2009

&&

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

$$

DISCUSSION...Kuhlman
AVIATION...Young/Smith
FIRE WEATHER...Kuhlman
CLIMATE...18