088
FXUS65 KPSR 150546
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1046 PM MST Thu Nov 14 2024

.UPDATE...
06z Aviation Discussion.

&&

.SYNOPSIS...
Tranquil conditions along with near to above normal temperatures
will prevail today. Starting on Friday and continuing through the
upcoming weekend, conditions will turn much cooler as a low
pressure system impacts the region. Along with the cooler
temperatures, there will also be breezy to windy conditions and
some slight precipitation chances mainly across southeast AZ.
Another follow-on system early next week may keep temperatures
below normal and bring another slight chance for precipitation.

&&

.DISCUSSION...
Water vapor imagery this afternoon shows the Desert Southwest
still under the influence of ridging, but a prominent trough is
now moving into the western CONUS. The ridging today is leading to
another pleasant day across the region with light winds, clear
skies, and slightly above normal temperatures, reaching the
upper-70s to lower-80s this afternoon.

Beginning tonight and Friday morning, the 700mb jet with the
incoming trough will overspread the area. This will lead to
increased winds across the region, with the most notable winds,
as indicated by high values in the EPS EFI, expected along and
north of the Mogollon Rim and in the San Diego Mtns, with
potential for downsloping and mountain rotors into Imperial
County. A Wind Advisory has been issued for western parts of
Imperial County beginning this evening that will run through
Friday evening, as wind gusts will be capable of reaching up to
45-55 mph. Advisory- level wind gusts (40+ mph) may be observed
elsewhere in some other areas outside the current advised area.
HREF probability of 40+ mph gusts is upwards of 40-50% in other
parts of Imperial County, including the Imperial Valley tonight
and Friday evening. Elsewhere around the lower deserts, winds will
no be as strong as Southeast CA, but still breezy Friday with
afternoon gusts up to 20-30 mph. Aside from the winds Friday, a
cold front will move through in the morning and lead to a
cooldown of temperatures by 5-10 degrees between this afternoon
and Friday afternoon.

Models remain in good agreement with the evolution of this coming
trough, having the trough eventually become a closed low just
south of the AZ and CA borders by Sunday. With the slow
progression, another 5-10 degrees of cooling is expected into
Saturday as 850mb temperatures are forecast to go from 17-18C this
afternoon all the way down to 4-5C by Saturday morning. Afternoon
highs are forecast to only climb into the middle-60s Saturday
across the lower deserts, which is 10 degrees below normal.

Upper level ridging and generally clear skies across the region
today will allow for a bit warmer temperatures with highs reaching
into the upper 70s across the western deserts to the lower 80s
across the south-central Arizona lower deserts. However, not far
behind is a Pacific weather system which will track southeastward
toward the region by tonight. The system is expected to be quite
dry and the first piece of energy from the system is forecast to
bypass our area to the northwest before lifting through the Great
Basin on Friday. However, the system will still bring in some
modestly cooler air on Friday with highs dropping down closer to
70 degrees across the lower deserts. Breezy to locally windy
conditions are also likely to occur mainly in the afternoon Friday
with the strongest gusts of up to around 35 mph focused across
Imperial Co. California. Winds will not be much lighter Saturday,
compared to Friday, as the 700mb jet will have already shifted
off to the east. As for the prospect of rain with this system, the
best chances will remain in Southeast AZ and on the windward side
of the San Diego Mtns. There will be a decent IVT plume (300-400
kg/ms) streaming in from the Pacific ahead of the trough, but it
will be focused through northern Mexico and just barely clip into
Southeast AZ late Saturday into Sunday. NBM PoPs peak around
20-25% in Southern Gila Co. Sunday morning and afternoon, that
quickly drops off to the west to 5% or less in Phoenix.

This weekend`s system should move out of the area through Monday
morning, but temperatures will remain well below normal through
Monday, with lower desert highs in the 60s to lower-70s and
morning lows in the 40s. After Monday, there is still tremendous
uncertainty amongst global models with the evolution of the next
follow-on system Tuesday. The global ensembles remain split almost
50-50 on a progressive open wave clipping through AZ, composed of
mostly GEPFS and GEPS members, versus a slower-moving trough that
closes off in AZ and/or NM, composed of primarily EPS members.
This uncertainty is leading to a large spread in forecast
temperatures, precipitation chances, and possible breeziness.
Unsurprisingly, the EPS solutions produce colder temperatures and
better precip chances. The NBM deterministic official forecast is
sitting right around he median of the NBM ensemble solutions for
Tuesday and Thursday, where the forecast high temperature
interquartile spread is upwards of 10-15 degrees, ranging from
lower-60s to middle-70s. With the trajectory of this follow-on
system the greatest precip chances will favor the AZ higher
terrain and along a potential cold front. NBM PoPs are currently
up to 20-30% in the higher terrain north and east of Phoenix, and
less than 15% in Phoenix, that drops to 0% by the Lower CO River
Monday night through Tuesday morning.

Amplified ridging across the western CONUS is then favored by the
second half of next week, which should yield a return of more
tranquil conditions and warmer weather.

&&

.AVIATION...Updated at 0545Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation weather concerns are expected through the forecast
period. Winds will follow typical diurnal tenancies with light
easterly flow tonight followed by an earlier than normal shift
back to westerly by 16Z-17Z tomorrow morning. There could be a few
gusts into the upper teens to possibly as high as 20 kts tomorrow
afternoon, mainly at KDVT and KPHX. Intermittent high clouds will
pass over the forecast area through early tomorrow before skies
clear out.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation weather concerns besides breezy conditions are
anticipated over the next 24 hours. Elevated westerly winds will
continue overnight and through much of tomorrow at KIPL with gusts
reaching 25-30 kts at times. KBLH will see S-SW winds through
tomorrow with gusts increasing to around 20 kts by the afternoon.
High clouds are expected to increase in coverage tonight, but
should clear out of the region by early tomorrow morning.

&&

.FIRE WEATHER...
Very dry conditions remain over the region today with a weak high
pressure system moving to the east before a mostly dry Pacific
low pressure system begins to affect the region starting Friday.
Expect breezy to locally windy conditions later on Friday across
the western districts along with improved humidities and
temperatures falling to below normal. MinRHs into the weekend
will mostly range between 20-30% across the lower deserts with
lighter winds returning to the area. The weather system will
mostly bypass the region to the south over the weekend with any
light precipitation potential mainly over the Arizona high
terrain. Expect well below normal temperatures to last into early
next week with humidities gradually trending lower.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Wind Advisory until 1 AM PST Saturday for CAZ562-566.

&&

$$

DISCUSSION...Benedict
AVIATION...Salerno
FIRE WEATHER...Kuhlman