FXUS65 KPSR 111100

Area Forecast Discussion
National Weather Service Phoenix AZ
400 AM MST Mon Dec 11 2023

Updated Aviation


Warming temperatures to start the workweek with a brief cool down
expected by midweek as a low pressure system moves through Arizona.
While dry conditions are expected for the majority of the area
through at least next weekend, the previously mentioned low pressure
system will bring a slight chance of showers to the higher terrain
in southern Gila County late Wednesday into early Thursday morning.
Once this low pressure system passes through high pressure will
build back in over the region leading to a warming trend for the end
of the workweek and the weekend.


Streamline analysis this morning shows quasi-zonal flow over much of
western CONUS with a trough beginning to dig over northern
California. Upper-level WV imagery reveals a plume of Pacific
moisture moving over southwestern CONUS. This plume of Pacific
moisture will increase upper-level moisture causing considerable
cloudiness building in across Arizona throughout the day today. FEW-
SCT high clouds this morning will result in another chilly morning
with lows dipping into the low-to-mid 40s across the much of the
lower deserts and mid-to-upper 30s across the higher terrain and
rural deserts. Increasing cloud cover this afternoon will result in
suppressed afternoon high temperatures with the lower deserts seeing
afternoon highs in the upper 60s and low 70s and the higher terrain
topping out in the mid 60s.

Increased cloud cover overnight tonight will lead to warmer morning
lows on Tuesday. Tuesday morning lows will be in the mid-to-upper
40s and low 50s for much of the lower deserts and in the low 40s for
the higher terrain and rural deserts. Cloud cover will decrease
across the region on Tuesday as the trough digs into southern CA and
western Arizona pushing the plume of Pacific moisture and associated
clouds to the east of our region. Clouds exiting the region on
Tuesday will allow for slightly warmer afternoon temperatures on
Tuesday than today.

Deterministic and ensemble models show the trough continuing to
deepen and becoming a cutoff low in northern Arizona early Wednesday
morning. However, there does still remain some discrepancy on the
exact strength and position of this cutoff low. This cutoff low will
bring decreased heights aloft on Wednesday which will allow for a
slight cool down. Afternoon high temperatures will be in the upper
60s and low 70s across the lower deserts and in the low-to-mid 60s
across the higher terrain. The cutoff low overhead on Wednesday will
result in breezy conditions across southeast California and the
Colorado river valley Wednesday afternoon, with gusts of 20-25 kt
possible. Most of the region will remain dry as this system passes
through due to the lack of moisture as PWATs will range from 0.2-
0.4” across the CWA. The highest moisture will be in place over the
higher terrain in southern Gila County. While chances are low,
around 20% or less, there may be enough lift to squeeze out a few
sprinkles or light showers across the high terrain in southern Gila
County late Wednesday night into early Thursday morning.

The cutoff low will quickly exit the region to the east with a ridge
moving in on Thursday. The ridge building in will allow for a slight
increase in temperatures on Thursday. This ridge will continue to
build and amplify over the region heading into the weekend. This
high amplitude ridge will result in temperatures well above normal
for the end of the workweek and for the weekend. Daily afternoon
high temperatures are currently forecasted to be 8-12 degrees above
normal this weekend.


.AVIATION...Updated at 1100Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:

No weather issues will exist through Tuesday morning under
occasional periods of thicker high cirrus. Confidence is very good
that light east winds will be common most of the period around the
Phoenix metro with only a brief window around sunset where
directions shift to westerly. N/NW winds will be preferred in SE
California with extended periods of nearly calm conditions likely.


With high pressure overhead, temperatures will warm slightly through
Tuesday. Wind speeds will be light through Wednesday morning and
generally be under 10 mph. Relative humidity values will range from
10-15% this afternoon and Tuesday afternoon. Overnight recovery will
be poor to fair and range from 15-35%. A low pressure will move
through Arizona on Wednesday and exit on Thursday. This system will
cause a slight increase in moisture with afternoon RH values ranging
from 15-25% on Wednesday and Thursday. This system will also bring
elevated wind speeds of 20-25 mph to SE CA and the CO river valley
Wednesday afternoon. While most of area will remain dry, a few
showers will be possible in the high terrain in southern Gila County
Wednesday night into Thursday morning. Wetting rainfall not expected
with this system.





FIRE WEATHER...Berislavich