Mesa, Arizona Weather Forecast Discussion

302
FXUS65 KPSR 122342
AFDPSR
Area Forecast Discussion
National Weather Service Phoenix AZ
442 PM MST Fri Sep 12 2025
.UPDATE...00Z Aviation Discussion.
&&
.KEY MESSAGES...
- Near to slightly below-normal temperatures will prevail through
  the weekend before a gradual warming trend materializes heading
  into early next week.
- Isolated to widely scattered showers and thunderstorms expected
  this afternoon across southern Gila County before much drier
  conditions develop this weekend and extend into early next week.
&&
.SHORT TERM /TODAY THROUGH SATURDAY/...
The latest Water Vapor Satellite Imagery depicts a highly
amplified upper trough situated over Nevada and the subtropical
high situated over the southern Plains. Due to the influence from
the upper trough, southwesterly flow aloft continues to influence
much of the Desert Southwest with very dry air entrenching much of
southern CA through western AZ. To the east of surging dry air,
lingering moisture continues to be situated across the eastern
third of AZ. Forcing for ascent from an upper-level jet streak
moving through northern AZ has resulted in several rounds of
scattered thunderstorms across much of the eastern third of the
state, including portions of southern Gila County, this morning.
With the jet-forced ascent remaining in place along with favorable
moisture and instability profiles, additional rounds of scattered
thunderstorm activity will continue through this afternoon and
early this evening across much of the eastern third of AZ with dry
conditions persisting elsewhere. Some of the storms that develop
through the afternoon may reach severe levels given that there are
30-40 kts of deep-layered shear in place. The primarily hazards
will be strong gusty winds, marginally severe hail and locally
heavy rainfall.
By Saturday, as the upper-level trough axis moves through the
region, the dry air will continue to surge eastward, scouring out
most of the moisture as PWATs plummet to around 50% of normal to
around 0.40-0.60". Thus, rain chances will be mostly eliminated
with mostly clear skies prevailing. Temperatures during the next
couple of days will continue to average near to slightly below-
normal with highs in the mid to upper 90s across the western
deserts and near 100 degrees across the lower deserts of south-
central AZ, although temperatures are likely to stay below century
mark on Saturday. Early morning low temperatures will also cool
off to very comfortable levels with readings in the mid to upper
60s across the cooler rural areas and low to mid 70s across the
urban corridors.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Following the passage of the trough on Saturday, the synoptic
pattern across the Desert Southwest will enter a relatively weak
westerly flow regime, with no considerable synoptic scale or large
scale features impacting the region, through at least the first
half of next week. This will allow temperatures to remain near
seasonal levels, with lower desert high temperatures forecast to
reach right around the century mark each day and mornings
continuing to start out in the 70s. Global ensembles do show a
gradual trend toward positive 500mb height anomalies by the middle
of next week, which will support a gradual warm-up. Latest NBM
forecast has high temperatures return to a couple of degrees above
daily averages by Tuesday or Wednesday.
This weak flow pattern heading into early next week will allow
for at least a slow return of PBL moisture from the southeast, but
afternoon shower and storm chances during the first half of next
week will mostly favor Southeast AZ, with NBM PoP at or below 10%
across South-Central AZ.
The overall picture becomes less clear by the second half of next
week with a highly variable forecast. There is a high degree of
uncertainty as the synoptic flow pattern looks to remain pretty
weak and messy and then there is the potential for tropical
moisture advection into the region stemming from what is forecast
to become Tropical Storm Mario off the west coast of Mexico. As
of now, models generally favor the track of this system remaining
off the western coast of the Baja Peninsula before eventually
falling apart. However, some models want to bring remnant
tropical moisture into the southwest deserts and coastal area,
which could result in considerable cloud cover and even rain
chances. Subtle shifts in the forecast could yield vastly
different foreast solutions for this timeframe, so how this
potential system evolves will be something to monitor in the
coming days. The interquartile ranges on forecast temperatures
from the NBM are currently around 7-10 degrees across Southern AZ
and SoCal beginning Friday and the ranges on PWAT are around
0.4-0.6".
&&
.AVIATION...Updated at 2340Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation concerns are anticipated through the forecast period.
Any lingering convective activity will remain over the high
terrain east of the Phoenix metro. Winds will follow typical
diurnal patterns with a few gusts into the teens to around 20 kts
through sunset before becoming light out of the ESE late tonight.
FEW-SCT mid and high clouds will gradually dissipate, leading to
clear skies overnight.
Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns are expected through the forecast period.
Winds will remain out of the west at KIPL, with a brief period of
gusts upwards of 25 kts this evening. At KBLH, winds will be
primarily out of the southwest, becoming light and switching to
the northwest early Sunday morning. Mostly clear skies will
prevail over SE California through the TAF period.
&&
.FIRE WEATHER...
Near to slightly below normal temperatures will be common across
the region through this weekend thanks to an area of low pressure
passing to the north. Outside of some breezy conditions this
afternoon with peak gusts around 20-25 mph, winds over the next
several days will favor familiar diurnal trends. Most of the
forecast area will remain dry, but some slight chances of wetting
rains do exist for the foothills and high terrain east of Phoenix
through this afternoon. MinRHs over the next few days are likely
to range from 10-15% across the western districts to 15-25% across
the eastern districts. By this weekend, even drier conditions are
expected.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
SHORT TERM...Lojero
LONG TERM...Benedict
AVIATION...Salerno
FIRE WEATHER...Benedict/Lojero

NWS PSR Office Area Forecast Discussion