406 
FXUS65 KPSR 191705 AAB
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1005 AM MST Tue Oct 19 2021

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS... 
Temperatures will remain well below normal on Tuesday in the wake
of a departing dry storm system. High pressure will build back 
into the region during Wednesday through the weekend allowing 
temperatures to rebound back near the seasonal normal. Dry weather
should persist through at least the end of the week. A more active
weather pattern is potentially in store early next week.  

&&

.DISCUSSION...
The breezy conditions from Monday have mostly subsided, with
exception to a few locations in southern Gila County still gusting
to around 20 mph early Tuesday morning. The center of a well-
defined mid-level cyclone is over eastern Utah, with an extensive
belt of dry air aloft extending across northwest Mexico and the
Desert Southwest. Suppressed mid-level heights extend through this
corridor as well, which will act to keep temperatures several
degrees below normal across the entire forecast area. Phoenix is
only forecast to top out at 80 degrees, and has a 32% chance of
remaining in the 70s according to the NBM. High temperatures in
the 70s may in fact be realized in many other desert locations, 
such as Yuma, El Centro, and Chiriaco Summit, CA. 

More benign weather will temporarily take hold as shortwave
ridging becomes established amidst an increasingly quasi-zonal
flow regime. This will usher in a warming trend with temperatures
returning closer to normal (upper 80s) by the end of the workweek.
Lighter winds can also be expected. Bulk of medium-range
deterministic and ensemble guidance is beginning to ply a more
consistent evolution of stronger quasi-zonal flow impinging into
the western CONUS later this weekend, with a more significant
shortwave trough evolving early next week. As is typical several
days out, details regarding the exact timing of more significant
weather impacts is still very uncertain. But a general period of
increasing winds, cooler temperatures, and perhaps increased
precipitation potential looks possible. The primary focus for
heavier precipitation amounts currently remains focused to the 
north and along coastal areas of California, but small deviations 
in the pattern evolution could bring a different solution. 

&&

AVIATION...Updated at 1705Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: FEW-SCT 
cloud layers with bases in the 8-12k foot range to clear by this 
afternoon as drier air moves into the region. CLR skies will then 
prevail through tonight before SCT high cloud decks aoa 25k feet 
move into the region on Wed. Otherwise, winds will remain light with 
speeds AOB 8 kts the majority of the time. Wind directions will 
follow a more typical diurnal pattern with easterlies becoming 
southerly late morn/early aftn (oscillating between SSE-SSW), and 
then westerly by 21/22z. The nocturnal easterly switch is 
anticipated to occur after 06z late this evening. Light westerly 
winds to return on Wed afternoon.

Southeast California/Southwest Arizona including KIPL and KBLH: 
Winds will remain significantly lighter compared to yesterday with 
speeds mostly remaining AOB 10 kts. At KIPL, directions will favor 
the west with some periods of variability. At KBLH, winds will favor 
the north to northwest with extended periods of light/variable winds 
likely.

&&

.FIRE WEATHER...
Thursday through Monday: 
High pressure will be in place across the Southwest, bringing
generally light and diurnally driven winds. Temperatures will
climb back into the upper 80s to near 90 Thursday through the
weekend. Min afternoon RH values will mostly fall between 10-20%
across the lower deserts to 20-25% across the high terrain.
Overnight recoveries will mostly reach between 30-50% through the
period. A more active weather pattern will begin to develop Sunday
and Monday, and could bring increasing breeziness to parts of the
forecast area, along with cooler temperatures. 

&&

.SPOTTER INFORMATION STATEMENT... 
Spotters should follow standard reporting procedures.

&&

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

$$

DISCUSSION...Rogers 
AVIATION...Percha/12
FIRE WEATHER...Rogers