574
FXUS65 KPSR 081713
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1013 AM MST Fri Nov 8 2024

.UPDATE...Updated 18z Aviation Discussion.

&&

.SYNOPSIS...
Temperatures today will still be unseasonably cool, around 7 to 10
degrees below normal. As a lingering weather system departs the
Desert Southwest over the next day or so, a warming trend should
carry us into next week. A transient weather system during the first
half of next week should stay mostly north of the region cooling
temperatures by a few degrees before they rebound to slightly above
normal during the latter half of next week. Dry conditions are
likely to persist for the next 7 days.

&&

.DISCUSSION...
Mid-level water vapor imagery reveals a strong cyclonic circulation,
with analyzed H5 heights below 560 dam at its core, currently
centered over western New Mexico. With the associated column of cold
air still lingering over eastern AZ, another unseasonably cool day
is in store for the forecast area. Some localized spots across the
rural and higher elevation desert communities of South-Central AZ
may touch the freezing mark this morning, though with much less
coverage than what was observed early yesterday morning. As such,
no further freeze products were issued. Ensembles remain in
excellent agreement that the upper low over New Mexico will exit
the Desert Southwest over the next 24-36 hours, with weak ridging
building in its wake this weekend. This will make for a trend of
warming temperatures. Lower desert highs are expected to near 80
degrees by Sunday, which is about the average for this time of
year, and reach the lower 80s by Monday.

During the first half of next week, a shortwave trough is expected
to enter the Western US, with cluster analysis still indicating
notable differences in its amplitude between ensemble members.
Differences in amplitude are also quite apparent when comparing mean
H5 height fields between the ensembles, with the European deeper
than the others. However, guidance has started to come into better
agreement on timing. The vast majority show the base of the trough
remaining well north of the forecast area and passing to the east
sometime Tuesday. The sensible weather impacts from this system
passage would be a brief spell of slightly cooler temperatures and
locally breezy conditions in the typical wind prone locations. In
the wake of this trough, heights aloft should rebound, making for a
warmer latter half of next week. A more amplified ridging pattern
seems likely during the latter half of next week compared to what we
expect this weekend, especially if the trough passes as quickly as
most ensemble members advertise. This could lead to temperatures
reaching an above normal category, with highs likely remaining in
the 80s (NBM probabilities at 50-70% for 80+ degrees Wed-Fri next
week) for the typically warmer lower desert locales. However,
guidance spread increases considerably Tuesday onward. Despite
forecast uncertainty, confidence remains quite high that dry
conditions will prevail through the next 7 days.

By next weekend, guidance is beginning to hone in on a deeper trough
capable of bringing moisture and precipitation chances into the
forecast area. This is quite far out, but all global models depict a
similar positively-tilted trough orientation (dynamics not as
favorable for precipitation), with its base likely reaching
somewhere off the Baja California Coast before moving inland. Timing
and other specifics of this next system are still very uncertain, so
we will be keeping an eye on how this evolves in subsequent
forecasts.

&&

.AVIATION...Updated at 1715Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT;
Southeast California/Southwest Arizona including KIPL and KBLH:
Light winds, mostly at or below 7 kts, are expected at all
terminals into Saturday. Wind directions will tend to follow
typical diurnal tendencies, but there will be extended periods of
light variability at all terminals. SKC will prevail.

&&

.FIRE WEATHER...
Below normal temperatures continue today, with a gradual warming
trend to near normal over weekend into early next week. Winds
will follow more typical diurnal upslope/nocturnal drainage
components starting today. MinRHs will fall mostly between 10-20%
today and 10-15% this weekend, with readings closer to 25% over
higher terrain of eastern districts. Overnight recoveries tonight
will be better in the eastern districts, mostly between 40-60%,
with poor to fair overnight recoveries (around 20-40%) for the
western districts. Saturday and Sunday night recoveries will
generally fall between 20-45% across the area. Overall, dry
weather will persist through early next week and conditions will
remain favorable for any prescribed burning operations.

&&

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

$$

DISCUSSION...Whittock
AVIATION...Frieders
FIRE WEATHER...Whittock/18