-- Discussion containing changed information from previous version are highlighted. --
720
FXUS65 KPSR 241149
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
449 AM MST Mon Jun 24 2024

.UPDATE...
-- Changed Discussion --
12Z Aviation Discussion.
-- End Changed Discussion --

&&

.SYNOPSIS...
Daily thunderstorm chances will persist through most of this week
due to enhanced moisture levels lingering across the region, as
temperatures will continue to run several degrees above normal.
Building high pressure will warm temperatures by a few degrees
going through the middle of the week, resulting hot and humid
conditions over the next week.

&&

.DISCUSSION...
Showers and some thunderstorms continue to persist early this
morning across central to southern Arizona. Water vapor imagery
shows continued mid to high level clouds draped across the
region, as subtropical ridging centered over Texas is advecting in
enhanced moisture levels from the subtropics from a previous
tropical disturbance that has moved onshore of central Mexico.
PWATs continue to run upwards of 200% of normal, as latest SPC
mesoanalysis depicts PWAT`s as high as 1.90" across southcentral
and southwestern Arizona.

These enhanced moisture levels will result in more shower and
thunderstorm potential this afternoon and evening once again
across the region. However, relative to the previous several days,
the potential is trending downward as the anomalous moisture axis
migrates westward today. More scattered to mostly clear conditions
should be in store today, so diurnally driven convection could
become more of a factor. The latest HREF shows mean surface-based
CAPE values of 500-1000 J/kg over the higher terrain areas of
southcentral Arizona, so there is sufficient instability. However,
boundary layer capping and subsidence aloft will be limiting
factors towards convective development as we progress through the
week. For today, shower and thunderstorm chances continue to run
around 25-45% across the higher terrain, but only 10-20% for the
lower deserts across southcentral Arizona. The mean low to mid-
level flow is much weaker today, so the potential of showers and
storms migrating into the lower elevations will be dependent on
cold pool maintenance, which, given the elevated moisture levels,
will not be favorable to pack much of a punch should any outflows
reach the lower deserts (similar to what happened overnight, where
only weak showers developed across the valley floor of the Phoenix
metro). That being said, there are a couple of HREF members
painting 40+ dbZ cores that migrate from the east into the Phoenix
metro late this evening, so will have to keep an eye on how things
evolve throughout today. Strong outflow wind probabilities
continue to run low as HREF probabilities of 35+ mph wind gusts
remain around 10-30% across the higher terrain and lower
elevations of southcentral Arizona.

Shower and storm potential is anticipated to continue to diminish
going through this week, as the aforementioned strong ridging
centered over Texas will continue to build westward across the
region. The peak height anomalies, as depicted by the ensembles,
is set to occur Tuesday into Wednesday, as mid-level heights
build between 594-597 dam. Temperatures will trend warmer as a
result, with most lower desert locations seeing highs in excess of
110 degrees by the middle of this week. Widespread Moderate
HeatRisk will continue, with localized (>10% areal coverage) of
Major HeatRisk across the region. Despite PWAT`s generally in
excess of 1.50" across the region, this stronger ridging will
again inhibit daily thunderstorm activity going through the middle
of the week, as NBM PoP/thunderstorm chances decrease to around
20-30% for higher terrain areas of southcentral Arizona and 5-15%
for lower desert areas by Wednesday. As moisture levels continue
to wane going through the rest of the week, shower/storm chances
diminish to less than 10% (10-20%) for the lower deserts (higher
terrain) by Friday.

These moisture levels will diminish due to a troughing feature
that will skate across western CONUS mid to late week, ushering
in more dry westerly flow to the region. Ensembles are in much
better agreement of this trough lowering heights through at least
Friday, with slight cooling going into this weekend. Cluster
analysis shows mid-level heights beginning to rebound over the
weekend, with generally good agreement through at least Saturday.
There is more spread regarding a secondary wave moving into the
Pacific Northwest Sunday onward, which will dictate whether the
building heights will continue into next week, or if temperatures
may remain moderated, but still above normal, during this period.

&&

.AVIATION...
-- Changed Discussion --
Updated at 1150Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:

VFR conditions will prevail through the forecast period. Expect
a few hrs of light and variable winds at KPHX early this morning
before westerly flow becomes reestablished by 15Z-16Z. Westerly
winds will continue throughout the day at all metro terminals.
Convection is expected to develop again this afternoon and early
evening across the higher terrain north and east of Phoenix.
There is a low chance (<20%) that outflows from distant storms
will reach KPHX later this evening, however most model guidance
suggests winds will continue to remain westerly tonight. Abundant
mid to high lvl clouds will slowly become FEW to SCT through this
afternoon before thickening up again this evening.


Southeast California/Southwest Arizona including KIPL and KBLH:

At KIPL, winds should remain light out of the southeast through
much of the day before shifting out of the southwest around
sunset. At KBLH, expect southerly winds to prevail with gusts
reaching 20 kts at times this afternoon. Any convection that
develops this afternoon should remain east of the Colorado River.
FEW-SCT cirrus will continue to pass over the area into tonight.
-- End Changed Discussion --

&&

.FIRE WEATHER...
Monsoonal moisture will continue to result in daily chances for
shower and thunderstorm activity, with the best chances for
activity across the higher terrain areas. Shower and thunderstorm
chances will gradually diminish throughout the week, as high
pressure builds into the region. With the elevated moisture in
place, MinRH values through early this week will range between
30-40% across the far eastern districts to between 15-25% across
the western districts before slowly drying into the middle to
latter half of next week. Winds will follow their typical daily
tendencies, with gusty outflows from any thunderstorm activity
anticipated over the next several days. Temperatures through today
will average near to slightly above normal before increasing some
heading into the middle of this week. Chances for wetting rains
will generally remain around 10-20% for the higher terrain areas
and 5-10% for the lower deserts of south-central Arizona through
the first half of the week.

&&

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

$$

DISCUSSION...Lojero
AVIATION...Salerno
FIRE WEATHER...Young/Lojero