749
FXUS65 KPSR 131833
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1133 AM MST Tue Aug 13 2024

.UPDATE...Updated 18z Aviation Discussion.

&&

.SYNOPSIS...
Thunderstorm chances this afternoon and evening will be confined to
the higher terrain locations in eastern Arizona. Drier air arrives
for the latter half of the work week causing little to no monsoonal
activity, even over the higher terrain areas. Slight uptick in
moisture this weekend will lead to a slight increase in thunderstorm
activity, mainly confined to the Arizona higher terrain.
Temperatures will remain largely unchanged through the weekend and
run near to slightly above normal.

&&

.DISCUSSION...
Analysis of upper-level water vapor imagery this morning shows the
subtropical high pressure system centered over Texas stretching back
into New Mexico. There is also an upper-level trough moving onto the
coast of the Pacific northwest. Over the next few days as this
trough moves further inland it will flatten out the subtropical
high, which will lead to westerly flow aloft bringing much drier air
into the region. Mid-level water vapor imagery shows this much drier
air already in eastern portions of CA and NV and starting to move
into far western portions of AZ. Current PWAT values of 1.0-1.5"
across the region will decrease slightly by this afternoon and
evening, but there will still be enough moisture to support the
development of isolated to scattered showers and storms across the
higher terrain areas in eastern AZ.

For the middle and end of the workweek, PWAT values will lower to
the 0.8-1.2" range across the region, which is unfavorable for
thunderstorm development. Global ensembles now show a secondary
upper level low pressure system digging into the Pacific northwest
on Thursday and Friday, which will delay the subtropical ridge from
building back into our region. NBM PoPs are now around 5% or less
across the entire CWA for Wednesday-Friday.

This weekend, as the aforementioned trough continues to dig off the
coast of the Pacific northwest, the subtropical ridge will start to
strengthen across NM/TX. This will result in a return of
southerly/southeasterly flow to the region and cause a slight
increase in moisture. In turn, daily storm chances return this
weekend and continue into the beginning of next week, with most, if
not all, activity confined to the higher elevation locations.

Temperatures will remain largely unchanged through the weekend.
Afternoon high temperatures will be in the 100-110 degree range
across the lower deserts and in the 90-100 degree range in the
higher terrain areas. Temperatures will be near to slightly above
normal, with HeatRisk in the Minor to Moderate range across the
region.

&&

.AVIATION...Updated at 1830Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Only minimal weather impacts are possible through Wednesday under
periods of FEW-SCT mid/high cloud decks. Winds will establish out
of the W over the next hour or so, with some gusty, erratic
behavior possible with the TS over the Central Valley as it moves
off to the northeast. The only terminal expected to have direct
TSRA impacts will be KSDL through 20Z. Some isolated shower
development (10% chance) will be possible later this afternoon
(after 22Z), but confidence is too low to include at this time.
Otherwise, west winds may hold well later than usual tonight, and
perhaps closer to sunrise Wednesday morning.

Southeast California/Southwest Arizona including KIPL and KBLH:
No weather issues will exist through Wednesday morning under
clear skies. Winds will maintain a southerly component varying
between a daytime SE and evening SW component. Gusts may be more
prevalent today with 20-25kt possible at both terminals.

&&

.FIRE WEATHER...
Shower and thunderstorms chances this afternoon and evening will be
confined to the higher terrain areas across eastern AZ. With any
thunderstorm activity, there will be strong winds along with the
potential for gusty outflows that can cause sudden wind shifts.
Thunderstorms will also contain localized heavy downpours and
frequent lightning. Drier air will move into the region for the
later half of the week with little to no thunderstorm activity
expected. Aside from thunderstorm winds, the winds will tend to
follow their typical diurnal tendencies with some afternoon upslope
breeziness near 20 mph. MinRH values today will be in the 20-30%
range across the AZ districts and in the 10-20% range across the CA
districts. For the remainder of the workweek, minRH values will be
in the 10-25% range across all districts. Overnight recoveries will
be in the 30-50% range. Temperatures though the week will remain
largely unchanged and run near to slightly above normal.

&&

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

$$

DISCUSSION...Berislavich
AVIATION...Whittock/18
FIRE WEATHER...Berislavich