Calexico, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

119
FXUS65 KPSR 291124
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
424 AM MST Thu May 29 2025

.UPDATE...Updated 12z Aviation Discussion...

&&

.KEY MESSAGES...

-Temperatures heating up through Friday, with highs peaking around
 100-105 across the lower deserts on Friday leading to areas of
 Moderate HeatRisk.

-An influx of tropical moisture over the weekend will bring
 widespread chances for showers and isolated thunderstorms,
 focused on Sunday.

-Below normal temperatures with highs around 95 degrees across the
 lower deserts are expected from Sunday through at least the
 middle of next week.

&&

.DISCUSSION...
The main forecast concern over the next week will be the
unseasonably high amount of moisture moving into the region this
weekend and the very good chances for rainfall on Sunday. The
current atmospheric picture shows an upper level low now just off
the coast of northern Baja with upper level ridging stretching
across Mexico into our region and extending all the way into
southern Canada. The upper level low is forecast to strengthen
over the next day or so, become cut-off from the northern stream
flow, and wobble just off the Baja coast through Saturday. The
ridging over our region will keep daytime highs near 100 degrees
today, even as an abundance of higher level clouds affects the
region. The high clouds are forecast to largely vacate the area on
Friday allowing daytime highs to top out between 100-105 degrees
across the lower deserts.

While the cut-off low remains sitting to our southwest over the
next few days, a tropical depression will be slowly drifting
northward toward the southern tip of Baja. This disturbance is
forecast to eventually dissipate by around Sunday near the
southern tip of Baja, but it will help to direct a good amount of
tropical moisture northward with the circulation around the cut-
off low bringing the moisture the rest of the way into our region
over the weekend. PWATs are forecast to rise from around 0.5" on
Friday to near 1" on Saturday, before peaking at around 1.25" on
Sunday. Surface dew points are also expected to gradually rise
through Sunday with readings topping 50 degrees by Saturday
evening before peaking around 60 degrees on Sunday. This amount of
moisture is very unusual for this time of year with the GEFS
showing PWATs reaching 250% of normal and the EPS at near 300% of
normal. Barring any significant changes in the strength and the
track of the cut-off low, it is looking like much of our area will
end up seeing measurable rainfall at some point from Saturday
evening through Monday morning.

For some perspective, Phoenix Sky Harbor has only seen measurable
rainfall on 38 separate days during the last week of May and the
first week of June since 1896. The last few times Phoenix recorded
measurable rainfall during this period was in 2015, 2008, 1994,
and 1992. The highest amount recorded during this period was
0.41" on June 3, 1915. For June 1st, Phoenix has only seen
measurable rainfall one time (1914). It is even more unusual for
Yuma to see any rainfall in the last week of May or in the first
week of June as it has only occurred on 11 separate days.

Guidance has been quite consistent showing good rain chances over
much of the area on Sunday with the latest runs adding to our
confidence that much of southern and central Arizona will see
measurable rainfall. As moisture increases on Saturday, we may see
a small swath of higher based showers develop, but the coverage
and amounts are expected to be limited. Once the main low center
nears our area on Sunday, rain chances will increase quickly by
the afternoon with widespread chances of 50-80%. Instability
should also increase enough to bring thunderstorm chances into the
picture by late Sunday morning, likely lasting through around
midnight Sunday. Forecast MUCAPE is not all that impressive, but
it seems plausible we will see a swath of 500-750 J/kg of CAPE
traversing the area just ahead of the low center later on Sunday
providing chances for some storms. Model soundings also show
enough shear for a few strong thunderstorms Sunday afternoon and
evening. Rainfall amounts are likely to vary quite a bit with some
areas barely seeing anything to a few locations possibly seeing
an inch or so. The latest WPC QPF shows amounts averaging around
0.1" or so along the CO River Valley, 0.3-0.4" over the south-
central Arizona lower deserts, to as high as 0.5-0.75" over the
higher terrain. The threat for any flooding is likely to be quite
small as the instability should be limited and the steering flow
will average 10-20 kts. As the cut-off low continues to track
across Arizona during the overnight hours Sunday night into Monday
morning, it is forecast to quickly weaken before tracking into
New Mexico by noon Monday. We may see a few lingering light
showers Monday morning over the higher terrain north and east of
Phoenix, but overall the bulk of the rain will be over.

Drier conditions are expected to move in behind the weather system
on Monday, but there now looks to be a second potential
disturbance diving southward off the coast of California during
this time. Guidance is still somewhat uncertain with the eventual
track of this second system, but its looking more likely it may
move directly through our region at some point next Tuesday or
Wednesday. However, even if it does move through moisture levels
are likely to be quite limited which may preclude any additional
rain chances.

Forecast temperatures for Sunday through the middle of next week
are still quite uncertain due to the unsettled weather pattern.
The latest NBM now shows highs between 90-95 on Sunday (may still
be too generous) with readings likely staying somewhere in the low
to mid 90s through around next Wednesday or Thursday. The
uncertainty in temperatures for Sunday is mainly from the expected
cloud cover and rain developing, while the uncertainty into the
middle part of next week is due to the potential track differences
with the second system. Either way it seems we will mostly likely
see several days of below normal temperatures for the start of
June.

&&

.AVIATION...Updated at 1124Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
No aviation weather concerns. The overall wind pattern will
continue to exhibit the typical diurnal tendencies with speeds aob
10 kts, with some occasional gusts into the low to mid teens this
afternoon/early evening. Light and variable winds will be common
especially during the diurnal transitions. FEW-SCT high clouds
will continue throughout the TAF period.


Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns. At KIPL, winds will remain out of
the SE through the rest of the period. At KBLH, winds will
fluctuate between the SSE and SSW. Overall wind speeds will be
aob 10 kts. FEW-SCT high clouds will continue throughout the TAF
period.

&&

.FIRE WEATHER...
Seasonably dry conditions will continue through Friday before
unsettled weather is expected over the weekend. Expect MinRHs
around 10% today and Friday before RHs quickly increase this
weekend. Winds will favor typical diurnal tendencies with
periodic afternoon gusts to around 15 mph through Friday. South
southwesterly winds are likely to be more dominant over the
weekend with afternoon gusts to around 20 mph. A weather system
moving through the region late Saturday through early Monday is
expected to bring 40-70% chances for wetting rains and a 20%
chance of thunderstorms, focused on Sunday. Below normal
temperatures are expected starting Sunday and lasting well into
next week. Humidities will stay elevated through early next week
before gradually lowering back to more typical levels by the
latter half of next week.

&&

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

$$

DISCUSSION...Kuhlman
AVIATION...Lojero/Ryan
FIRE WEATHER...Kuhlman