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000
FXUS65 KPSR 120927
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
227 AM MST Fri Apr 12 2024

.SYNOPSIS...
High temperatures will once again reach into the nineties across
the lower deserts Today under sunny skies. The passage of a weak
disturbance today and stronger system this weekend will lead to
daily widespread breezy to locally windy conditions during the
afternoon and evenings through at least Monday. The low passing
through late this weekend into Monday will also temporarily cool
temperatures back down to and below normal. Temperatures then warm
back up by the middle of next week.

&&

.DISCUSSION...
Widespread 90 degree temperatures were observed across the lower
deserts on Thursday and similar temperatures are expected again
today as afternoon highs reach 90-95F. The ridge of high pressure
over the area is now shifting eastward and southerly flow is
increasing on the western flank of the ridge and downstream of a
weak low off the coast of northern Baja, which is subtly evident
in WV satellite. The temperatures today will once again lead to
widespread Minor HeatRisk and this will continue through Saturday
as well, despite temperatures forecast to cool several degrees as
the height field decreases and 850mb temperatures cool with the
passage of the weak low and approach of a deeper low from the
northwest.

The temperature swing and breezy to windy conditions will be the
primary sensible weather impacts today through early next week.
The pressure gradient will tighten up beginning today across the
Desert Southwest, with height falls over the area, with the
passing weak low today, and height rises to the east as ridging
amplifies over the Plains and northern US Rockies. Widespread
20-30 mph southerly wind gusts are expected this afternoon and
evening, with highest lower desert gusts, up to 30-35 mph,
anticipated in Southwest AZ and along the lower CO river. Westerly
sundowner winds in Imperial County may also reach 30-35 mph this
evening. With the Plains ridge continuing to slide east on
Saturday, the pressure gradient will likely weaken slightly across
the eastern half of AZ, but height falls with the approaching deep
low along the CA coast should keep the pressure gradient tighter
to the west and again lead to 25-35 mph southerly wind gusts in
Southwest AZ and Southeast CA in the afternoon and evening. A
vorticity maximum and mid-level front swinging through SoCal
Saturday evening may lead to a stronger sundowner wind event in
Imperial County. NBM probability of advisory-level wind gusts (40+
mph) in Imperial County Saturday evening is upwards of 60-80%.
Odds are even higher (75-95%) on Sunday, which lines up with
another vorticity maximum rotating around the low and over the
lower deserts. This will also likely lead to widespread
breeziness (25-35 mph afternoon/evening gusts) again across the
region, as the low also begins wobbling its way eastward. The
breeziness across the region will likely continue through at least
Monday as the low continues to progress across the region.

Global ensembles have been pretty consistent in the track of this
deep low pressure and confidence is now high on the timing, with
the core of the low passing through northern AZ on Monday before
speeding up and ejecting east of AZ by Tuesday. As mentioned, this
will be a deep low with H5 heights forecast to fall below 560mb
in northern AZ, which is down around the 10th percentile of
climatology for this time of year. As a result, surface
temperatures will really cool off, especially on Sunday and
Monday. NBM forecast highs are only in the mid to upper 70s Sunday
across Southeast CA and Southwest AZ, with similar highs across
all lower deserts Monday. Temperatures will likely rebound pretty
quickly though, with the low departing quickly into the Plains on
Tuesday. Highs are forecast to return to near normal on Tuesday
and potentially beck to 90F by the middle of next week.

Odds of measurable precipitation in the Northern AZ high terrain
with the low have gone up slightly, but NBM PoPs for the lower
deserts remains under 10%. Light rain showers could still develop
in the southern half of AZ Monday, but with limited moisture
(PWATs up to 0.4-0.5") and the core of the low just north, odds
of seeing wetting rains (>0.10") is nearly 0%.

&&

.AVIATION...Updated at 0520Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Light winds will prevail through Friday morning at all terminals
with wind speeds generally aob 8 kts. Easterly winds should
reestablish over the next hour or so at KPHX. Mid-late tomorrow
morning (16-18Z), winds will begin to increase out of the SE-SSE.
A period of southerly crosswinds may cause some minor concerns
midday at KPHX and KDVT (17-20Z), with gusts developing into the
upper teens to around 20 kt. Directions switch decidedly SW later
in the afternoon, where gusts are expected to peak in the low-to-
mid 20s. Speeds will decrease but remain SW-W over the early
evening hours. SKC skies will prevail.

Southeast California/Southwest Arizona including KIPL and KBLH:
Light winds will prevail through early tomorrow morning at both
terminals, with speeds mainly aob 7 kts. Directions will favor SW
at IPL and S at BLH overnight, with extended periods of
variability possible. Winds become the primary aviation concern at
both terminals tomorrow. Gusty southerly winds will be the main
concern at BLH late morning and through the afternoon, whereas
gusty SW-W winds developing during the afternoon and into the
evening will be the main concern at IPL. Speeds in the mid-to-
upper teens with gusts upwards of 25-30 kts will be common at both
terminals. SKC skies will prevail.

&&

.FIRE WEATHER...
Dry conditions and near to above normal temperatures are expected
through Saturday, with highs in the low to mid 90s today and mid
to upper 80s Saturday. Temperatures then cool and moisture levels
nudge up slightly Sunday and Monday with the passage of a weather
system just to the north. This weather system, on approach to the
region and as it passes through, will lead to daily breezy to
locally windy conditions each afternoon and evening through at
least Monday. Wind gusts up to 20-30 mph are anticipated across
nearly all districts each day, with locally higher gusts up to
35-40+ mph in parts of southwest AZ, southeast CA, and southern
Gila County. These increased winds may lead to periods of elevated
fire weather conditions, as minimum RHs bottom out at or below
15% across the region today and Saturday and around 15-25% Sunday
and Monday. Overnight recoveries will be good through this
weekend, with max RHs upwards of 45-75%. Winds lower,
temperatures warm back up, and minimum RHs lower back to 15% or
lower by the middle of next week.

&&

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

$$

DISCUSSION...Benedict
AVIATION...Whittock
FIRE WEATHER...Benedict