FXUS65 KPSR 040456
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
956 PM MST Tue Dec 3 2024

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
Tranquil conditions are expected to persist over the Desert 
Southwest through the rest of this week. Unseasonably warm 
temperatures will also remain in the forecast for the region, with 
daily highs running a good 10 degrees or so above normal for this 
time of year. Generally dry conditions will continue, with perhaps a 
few isolated showers over higher terrain areas during the middle 
portion of the week.

&&

.DISCUSSION...
Large scale ridging continues to encompass much of the western 
CONUS, while an embedded upper-level low sits over California and
and the Baja Peninsula. This Rex Blocking pattern has provided 
the Desert Southwest with quiet and warm conditions for the past 
several days now and it will continue to do so through at least 
the remainder of this week and into the weekend. In the meantime,
temperatures across the region this afternoon will continue to 
run well-above normal for this time of year, with readings ranging
in the middle to upper 70s over the western deserts to the lower 
80s for the Phoenix metro. In fact, the forecasted high for 
Phoenix this afternoon is 82 degrees which, if achieved, will 
break the previous record high of 81 degrees set back in 1940.

The previously mentioned low will meander its way east toward our 
forecast area into Wednesday which will result in a slight dip in 
temperatures with highs generally in the 70s for the lower deserts. 
As this low slides eastward, it will also provide some increased 
moisture flux to the region, with PWATS increasing to 150% of normal 
for this time of year for the eastern half of our CWA. With better 
moisture availability, it is not out of the question that a few
orographically induced showers are observed over higher terrain 
areas during the middle portion of the week. NBM PoPs over the 
past 24 hours have increased noticeably over Gila County on 
Thursday and now sit around 20-40%. Even with a better moisture 
profile in place, rain over lower desert areas is not an 
expectation at this time.

Global models agree that the low will eventually park itself over 
Arizona for a good 24-36 hours before it deepens and sags further 
south, becoming centered over southern Arizona and northern Mexico
by Friday. This will allow for regional heights to increase 
slightly, translating to a minimal bump in temperatures for the 
end of the week and into the weekend. Model clusters agree that 
the Rex Block will inevitably break by late this weekend and into 
the start of next week. Ridging will continue to be the dominant 
feature as the blocking pattern dissolves but signs do point to a 
more progressive trough diving through the Intermountain West. 
Looking at projections, this disturbance is expected to take a 
more inland track so any significant increases in moisture content
is not anticipated, therefore, increased rain chances are also 
not likely. However, depending on where the coldest air migrates,
it could help to decrease temperatures to more seasonal values at
some point next week. 
 
&&

.AVIATION...Updated at 0456Z.

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

No major weather issues will exist through Wednesday evening 
under occasional passing high clouds. While winds have mostly come
around to NE/E at KDVT, KSDL, and KIWA, light westerly winds will
hold until around midnight at KPHX before shifting easterly. More
typical diurnal transitions are expected Wednesday at Phoenix area
terminals. Across SE California, W/NW winds will be preferred. 
Extended periods of nearly calm conditions or light variability 
are likely at all terminals.

&&

.FIRE WEATHER...
The ongoing stagnant weather pattern will keep dry conditions and 
above normal temperatures in place all week. Expect overall light 
winds each day somewhat following diurnal wind patterns, but with 
some breeziness mainly this morning across the higher terrain of 
eastern Arizona. MinRHs mainly in the teens can be expected over the 
lower deserts to as high as 30-40% over the Arizona higher terrain.

&&

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

$$

DISCUSSION...RW
AVIATION...Benedict
FIRE WEATHER...Kuhlman