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FXUS65 KPSR 061131
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
431 AM MST Sun Apr 6 2025

.UPDATE...Updated 12Z Aviation Discussion.

&&

.SYNOPSIS...
High pressure will spread into the region early this week leading
to a quick warm up and temperatures reaching above normal
starting Monday. The high pressure system will strengthen further
through the middle of the week resulting in highs steadily
climbing well into the 90s to around 100 degrees across the lower
deserts by Thursday. Dry conditions and clear to mostly clear
skies are likely through most if not all of the coming week.

&&

.DISCUSSION...
The main forecast concern for the coming week will be the building
heat and the likely areas of Moderate HeatRisk developing by
Thursday. The upper level trough that has brought cool weather for
the last several days is finally ejecting eastward out of our
region with increasing subsidence and ridging filling in behind
the system. As H5 heights increase to between 577-579dm by later
on Monday, our region will undergo modest warming pushing highs to
a few degrees above normal on Monday.

The large scale weather pattern will also become somewhat blocked
with the ridge staying put over the Intermountain West into
central Canada. By Wednesday, stronger ridging situated to our
southwest will shift northeastward into the Southwestern U.S.
Heights aloft will get another boost during this time with H5
heights rising to 584-586dm before eventually peaking on Thursday
at around 588dm. Temperatures will continue to trend upward
through the middle part of the week with highs back into the 90s
starting Tuesday and likely just above 95 degrees on Wednesday.
As the ridging peaks over our region late week, temperatures will
climb further with some lower desert locales likely reaching or
even topping 100 degrees on Thursday and Friday. Local daily
record highs are likely to be in jeopardy for at least Thursday
and Friday (see CLIMATE section below). We also expect areas of
Moderate HeatRisk to develop by Thursday which could have impacts
on those who are sensitive to the heat, and/or those who have
prolonged exposure to the heat without adequate hydration.
Boundary layer conditions will remain seasonably dry during this
time which will at least allow for efficient nocturnal cooling
and overnight lows mostly in the low to mid 60s outside of the
urban core areas.

By next weekend, ensemble guidance favors a large scale trough
moving into at least the Pacific Northwest and likely farther
south toward our region. There is still some model uncertainty
with the strength and the depth of the trough, but there is at
least strong evidence it will lead to a cooling trend. For now,
the NBM is showing highs falling back to around 90 degrees by
next Sunday. If any weather system does end up passing through our
region, it is quite unlikely it will contain enough moisture for
any realistic precipitation chances. We have higher chances of
just seeing an increase in winds which could lead to elevated
fire weather concerns.

&&

.AVIATION...Updated at 1130Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Winds will tend to follow their typical diurnal tendencies with
speeds generally aob 10 kt. Skies will remain mostly clear.

Southeast California/Southwest Arizona including KIPL and KBLH:
At KIPL winds will primarily be out of the west with a prolonged
period of light and variable winds from ~15Z through the early
evening. At KBLH, current NW winds will become light and variable
~16Z then go southerly early this evening then SW`rly for the
overnight hours. Winds speeds at both terminals will generally be
aob 8 kt through the period. Skies will remain mostly clear.

&&

.FIRE WEATHER...
High pressure will spread into the region over the next couple of
days leading to quieter and drier conditions. Expect generally
clear skies with MinRHs falling to around 10-15% area-wide.
Temperatures will also quickly warm over the next several days
with readings reaching above normal starting Monday before peaking
later in the week at around 15 degrees above normal. Overall light
winds are also forecast with directions mostly following diurnal
patterns.

&&

.CLIMATE...

Record high temperatures this week:

Date       Phoenix        Yuma        El Centro
----       -------        ----        ---------

Apr  9   102 in 1989   102 in 1989   104 in 1989
Apr 10   100 in 2018   100 in 1960    98 in 2018
Apr 11    99 in 2023   101 in 1936   100 in 2018
Apr 12    99 in 1936   102 in 1962   103 in 1940

&&

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

$$

DISCUSSION...Kuhlman
AVIATION...Berislavich
FIRE WEATHER...Kuhlman
CLIMATE...Kuhlman