Claypool, Arizona Weather Forecast Discussion

304
FXUS65 KPSR 231049
AFDPSR
Area Forecast Discussion
National Weather Service Phoenix AZ
349 AM MST Tue Sep 23 2025
.KEY MESSAGES...
-Dry and tranquil weather conditions along with temperatures warming
 to above normal levels can be expected through midweek.
-A much more active weather pattern is likely to set up by the end
 of the week into next weekend as a low pressure system brings
 increased shower and thunderstorm chances as well as much cooler
 temperatures.
&&
.SHORT TERM /Today through Thursday/...
Early morning water vapor satellite imagery depicts two upper-
level lows, one meandering off the southern CA coast and another
diving southward towards the Central Rockies with upper-level
ridging situated between these two features over the Desert
Southwest. This pattern configuration is the beginning of an omega
blocking pattern that will be in place through midweek. The
region will be under the influence of the upper-level ridge with
500 mb heights expected to increase during the next couple of
days, peaking in excess of 590dm Wednesday through early Thursday.
Increasing subsidence as well as decreasing moisture levels will
lead to near zero rain chances today and Wednesday along with
hotter temperatures. Afternoon high temperatures across the lower
deserts today will peak around 100 degrees to then warm even
further on Wednesday, with many of the lower desert communities
expected to top out near 105F, which will be a good 5-8 degrees
above normal. Temperatures of this magnitude will yield widespread
moderate HeatRisk with localized areas of major HeatRisk along
the vicinity of the Phoenix metro area.
Thursday will be a transition day to what is likely to become a
much more active weather pattern heading towards the end of the
week and into the upcoming weekend. The aforementioned low off the
CA coast is expected to migrate inland across central and
southern CA before slowly diving southward. As it does so, there
will be some increased moisture and upper-level dynamics in the
form of diffluence aloft, resulting in increased thunderstorm
activity across the higher terrain areas of eastern and
southeastern AZ during the afternoon and early evening hours.
Enough of a capping inversion will still exist across the lower
deserts to limit thunderstorm activity, however, outflows from the
higher terrain activity most certainty could move into the lower
elevations resulting in gusty winds and increased boundary layer
moisture, helping to set up the stage for what is to come
afterwards for Friday through at least the first part of the
weekend. Under the residual influence of the ridge, high
temperatures on Thursday are still expected to be several degrees
above normal with highs near 105 degrees across the lower deserts
of south-central AZ and slightly cooler readings in the low 100s
across the western deserts. These temperatures will still result
in widespread Moderate HeatRisk with localized areas of Major
HeatRisk along the vicinity of the Phoenix metro area once again.
&&
.LONG TERM /Friday through Monday/...
Model guidance has come into better agreement for Friday on the
track of the upper-level low, with the center likely to set up
near San Diego, yielding to a somewhat higher confidence forecast.
With the upper-level low setting up near San Diego, strong
moisture advection is expected during the day on Friday with
mixing ratios forecast to reach 12-13 g/kg, helping to yield
strong instability with the latest forecast soundings in Phoenix
showing CAPE values in excess of 1000-1500 J/KG. In addition, the
region will be located along the left exit region of an upper-
level jet streak, yielding strong divergence aloft and thus good
upper-level ascent. Combining these factors along with strong mid-
level flow yielding 0-6 km shear values in excess of 25-30 kts,
the recipe will be there for strong to potentially severe
thunderstorms to materialize across portions of south-central and
southeast AZ during the day of Friday. With the decent moisture
levels in place, these thunderstorms are likely to be very
efficient heavy rain producers, thus increasing the potential for
flash flooding. Given the increased potential for flooding, WPC
has placed much of eastern AZ in a slight risk for excessive
rainfall leading to flash flooding. Keep in mind that we are still
about three days out and things could still shift, especially
with the track of the upper-level low. However, if the current
model projections are correct, Friday looks to be a highly
impactful weather day across much of south-central and southeast
AZ.
Heading into the weekend, model guidance does diverge somewhat on
the trajectory of the upper-level low but still does maintain the
center to the west of the region. Thus, rain chances will likely
continue, especially on Saturday when there will still be decent
moisture and instability in place to potentially yield additional
thunderstorm activity. Thereafter, there are signs that by next
Sunday and Monday the upper-level low will be weakening and move
eastward, with drier air moving in and rain chances decreasing.
Temperatures starting on Friday and through the upcoming weekend
will cool off to below normal levels under decreasing heights
aloft from the approaching upper-level low as well as under the
influence of clouds and potential rainfall. Latest NBM shows
afternoon highs across much of the lower deserts only topping out
in the lower 90s, however, if the clouds and rainfall prove to be
more abundant then there is the potential for high temperatures
to be stuck in the 80s. Along with the cooler daytime highs,
overnight and early morning low temperatures will also cool down
with most areas bottoming out in the low to mid 70s, with some of
the cooler rural areas potentially dipping down into the 60s.
&&
.AVIATION...Updated at 1050Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation impacts are expected through at least Wednesday
morning. Winds will remain light (aob 8 kt) through the period
mostly following diurnal trends with periods of near calm winds
during transitions. Expect clear skies through the period.
Southeast California/Southwest Arizona including KIPL and KBLH:
Very light winds (aob 6 kt) will prevail at both terminals through
the TAF period with prolonged periods of VRB. Wind components will
still tend to favor an easterly component at KIPL and SE to N at
KBLH. Expect clear skies through the period.
&&
.FIRE WEATHER...
Dry conditions along with warming temperatures to above normal
levels will prevail through midweek. MinRHs today will be in the
20-30% range, before dropping into the 15-25% range on Wednesday
with fair to good overnight recoveries in the 30-60% range.
Heading towards the end of the week and into next weekend, a
slow-moving low pressure system will impact the region leading to
increasing moisture levels and rain chances with enhanced
probabilities of wetting rainfall, particularly across south-
central AZ. Winds will remain relatively light during the next
couple of days with some modest afternoon upslope gusts.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
SHORT TERM...Lojero
LONG TERM...Lojero
AVIATION...Kuhlman
FIRE WEATHER...Lojero

NWS PSR Office Area Forecast Discussion