874
FXUS65 KPSR 251141
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
441 AM MST Tue Jun 25 2024

.UPDATE...
12Z Aviation Discussion.

&&

.SYNOPSIS...
Enhanced monsoonal moisture across the region will continue to
allow thunderstorm chances to persist through most of this week,
with greatest chances today and tomorrow. Temperatures will
continue to run several degrees above normal, so hot and humid
conditions will persist as well during this period. Drier and
potentially hotter conditions possible heading into the weekend.

&&

.DISCUSSION...
Shower and thunderstorm activity have dissipated for the most
part across the region, after a very active
afternoon/evening/early overnight yesterday. The outlook for today
will be dependent on an ongoing convective complex that is mainly
across southern Arizona, as clearing skies will be necessary to
improve shower/storm chances across the region today. That being
said, higher terrain forecasted thunderstorm chances are still
around 30-40%, as HREF ensembles continue to show decent
instability in excess of 1000 J/kg. However, some low level
inhibition will moderate surface-based convection, as model
soundings would suggest surface parcels will need to rise several
thousand feet to realize the available instability, at least in
the higher terrain.

Based on the mean SE-E flow across the region, outflow activity
from convective activity along the Mogollon Rim looks less likely
to traverse over the higher terrain areas today, with the
consensus hi-res model analysis depicting most convective
activity remaining north of the region across Yavapai County.
Despite the mean flow being primarily easterly, the most
noteworthy shower/storm activity across the region may be the low
chance (15-25%) of southwesterly moving outflows that could spark
convection late this afternoon and evening across central to
western Maricopa County and eventually into La Paz and Yuma
Counties late this evening according to a couple of the HREF
members.

Otherwise, temperatures are expected to run several degrees above
normal today, as widespread Moderate HeatRisk persists. Heading
through the middle of the week, peak ridging anomalies will begin
to wane, as a troughing system begins to move into the Pacific
Northwest. This change in weather pattern will usher in some dry
westerly flow, which is the cause of lower moisture levels heading
into the weekend. Despite there being height falls across the
region through Thursday, temperatures will continue to hover
several degrees above normal as slightly drier conditions settle
into the region. Thunderstorm chances will wane as a result of
this change in pattern as well, with daily chances dissipating
below 15% for the higher terrain by Friday.

Heading into the weekend, the troughing feature over western CONUS
will slide off to the east, resulting in a rebound in mid-level
heights and a return of southerly to southeasterly flow, which
will enhance moisture levels once again. These trends are
generally the ensemble consensus at this point, but handling of a
secondary trough moving into the Pacific Northwest will dictate
the magnitude of building heights and increasing moisture levels
heading into next week. Due to these generalized trends, better
daily shower and thunderstorm chances would be on the increase for
eastern/southeastern regions of Arizona. Temperatures will
continue to hover several degrees above normal with this pattern
change, but no excessive heat is expected to develop over the
extended period at this time.

&&

.AVIATION...Updated at 1140Z.

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

VFR conditions with SCT-BKN mid to high lvl cirrus will continue
through the forecast period. Winds will start off easterly but
are expected to shift around to the SW by 17Z-18Z this morning.
Speeds should remain generally around 8 kts or less. Another
round of convection is expected to fire this afternoon, although
coverage does not look to be as extensive as yesterday and should
remain confined to the higher terrain to the north and east of the
Phoenix Metro. There is still a low chance (10-20%) of an outflow
boundary reaching KPHX this evening most likely after 00Z. High-
res models suggest that any outflow emanating from storms over
the high terrain will serve to enhance W to NW flow later this
evening, but we will monitor and amd as necessary.

Southeast California/Southwest Arizona including KIPL and KBLH:

VFR conditions are expected at the SE California terminals through
the period. Winds will continue to be southeasterly at KIPL and
southerly at KBLH through most of the day. Expect some breeziness
this afternoon with gusts up to 20-25 kts at KBLH. SCT mid to high
lvl clouds will progress over the region, otherwise skies should
remain mostly clear.

&&

.FIRE WEATHER...
Monsoonal moisture will continue to result in daily chances for
shower and thunderstorm activity. The higher terrain areas will
see the greatest potential with some locally heavy rainfall with
any storms that develop. Best chances for storms are today, with a
gradual decrease in chances/coverage through Friday, where chances
drop around 15% or lower. 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 today, before
dropping below 10% across the region starting Thursday. With the
elevated moisture in place, MinRH values through the middle of
this week will range between 30-40% across the far eastern
districts to between 15-25% across the western districts before
slowly drying during the latter half of this week. Winds will
follow their typical daily tendencies, with gusty outflows from
any thunderstorm activity anticipated over the next several days.
Temperatures average several degrees above normal through the
forecast period.

&&

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

$$

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