National Weather Service Raw Text Product

403 
FXUS65 KPSR 280557
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1057 PM MST Tue Oct 27 2020


.UPDATE...
Updated Aviation Discussion.

&&

.SYNOPSIS...
One more night of chilly temperatures is expected with freezing
temperatures possible in portions of southern Gila County, before
a strong warming trend begins later this week. High temperatures
will likely reach 90 degrees across the lower deserts by Sunday.
Much lighter winds are expected with no rain through the end of
this week. 

&&

.DISCUSSION... 
A well-defined upper low continues to slowly rotate near the
Arizona/New Mexico border this afternoon. Along it's western
periphery, cold advection continues out of the northeast along
with wrap-around moisture resulting in cloudiness across eastern
parts of Arizona. In fact, a few light showers and snow showers
were affecting southern Gila County up until early this afternoon,
before eventually weakening. The air mass left in the wake of this
storm system is cold and very dry. Dewpoints are in the upper
teens and low 20s across Arizona, and single digits to even below
zero near and west of the Colorado River. The breezy north winds
along the Colorado River are gradually weakening, and will result
in an end to the critical fire weather threat there.

One more night of very cold temperatures (for late October) is
expected this evening given the proximity of the upper low.
Similar to last evening, freezing temperatures are possible across
portions of southern Gila County, especially at the highest
elevations. There is higher confidence in more optimal radiational
cooling which could improve chances of freezing temperatures near
Globe, but overall the temperature profile may be slightly warmer
than yesterday morning. NBM probabilistic guidance suggests around
a 25% that Globe will drop to or below 32 degrees tonight. Across
the lower deserts, temperatures should be similar to what was
observed Tuesday morning, with some spots a few degrees warmer.

Another nice day on tap Wednesday with highs significantly below
normal - generally in the 70s across the deserts. Winds will also
be much lighter as the surface pressure gradient relaxes further.
A significant warming trend still is in the cards by later this
week as midlevel height rises occur in response to ridging
building off the California coast. This will bring temperatures
back into the 80s Thursday through Saturday, with low 90s
potentially more widespread by Sunday. Temperatures will be
flirting with record values by this point. The main uncertainty
for the temperature forecast during this period is how active the
southern stream will be over the Southwest, with some models
showing a weak disturbance late this weekend into early next week
which could potentially bring more upper-level cloud cover. Almost
all ensemble members suggest it will remain dry well into the
first week of November. 

&&

.AVIATION...Updated at 0557Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:

An upper low centered over southern New Mexico will continue to 
shift eastward tonight and Wednesday. Dry air in place will keep 
any skies clear. An easterly oriented surface pressure gradient 
will lead to surface winds favoring southeast and easterly 
directions the rest of the night and through the morning hours
Wednesday. Winds in the lower levels above the surface are 
expected to be relatively light and thus LLWS is not anticipated 
at the TAF sites. Surface winds Wednesday afternoon will be light
and favor southwest directions after 21Z. 
 

Southeast California/Southwest Arizona including KIPL and KBLH:

An upper low centered over southern New Mexico will slowly shift 
eastward tonight and Wednesday. At KBLH, surface winds will 
generally be light and variable with northerly directions being 
favored. At KIPL, surface winds will be light and favor 
southeasterly directions. Winds in the lower levels above the
surface are expected to be light enough to avoid LLWS criteria.
Otherwise, skies will be clear. 

&&

.FIRE WEATHER... 
Friday through Tuesday: 
Temperatures will warm through much of the period with above
normal readings and lower desert highs warming to around 90 
degrees by this weekend. Min RH will remain quite low through the 
period near 10-15%. Overnight recoveries will be around 25-40%. 
Winds will be relatively light each day with typical afternoon 
breezes and favoring typical diurnal tendencies.

&&

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

&&

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

$$

DISCUSSION...Rogers
AVIATION...AJ 
FIRE WEATHER...Rogers