Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/03/23

Area Forecast Discussion

National Weather Service Phoenix AZ

 430 PM MST Mon Oct 2 2023

.UPDATE...
Updated 00Z Aviation Discussion.

.SYNOPSIS...
A low pressure system will bring cooler conditions and occasional
breeziness to the Desert Southwest through this evening.
Thereafter, a warming trend is expected, though below normal
temperatures will persist through midweek. A return to above
normal temperatures is anticipated late in the week as high
pressure builds across the intermountain West. Drier than normal
conditions are also likely through much of the week along with
negligible rain chances. A slight increase in moisture is likely
Friday and Saturday, though slight rain chances will generally be
confined to eastern Arizona next weekend.

&&

.DISCUSSION...
Latest water vapor imagery reveals the upper low across western
Utah has become a bit more elongated as it continues to fill. A
well-defined upper-level front is also evident, which is bringing
much drier air to central Arizona above 700 mb. This is reflected
in morning ACARS soundings, which also indicate some moisture
around 800 mb resulting in scattered stratocu across portions of
Arizona. As the upper low moves eastward this afternoon, a trough
axis will sweep through central Arizona and bring a reinforcing
shot of cool air. Projected high of 87 degrees in Phoenix would be
the coolest day since early May.

Model ensembles remain in good agreement depicting the upper low
weakening and ejecting northeastward early this week. This will
result in a gradual warming trend as a ridge in the northern
Pacific migrates eastward across the intermountain West. Some
earlier ensemble members had suggested the potential of another
short-wave trough digging into the Desert Southwest midweek and
delaying the warming trend, however this now appears less probable
and forecast temperatures have even trended higher late in the
week. Latest NBM now suggests roughly a 70 percent chance of
reaching the 100 degree mark in Phoenix Friday.

Latest mean PWATs from the grand ensemble point to a gradual
drying trend through Thursday. Thereafter, a bump is low-level
mixing ratios appears more likely Friday/Saturday as easterly flow
around the ridge transports moisture in New Mexico westward into
Arizona. Nevertheless, there is still considerable uncertainty and
CAPEs Saturday range from as little as 0 to 1000 J/kg. Negligible
rain chances will continue through much of the week, followed by
5-20 percent PoPs Saturday, mainly across eastern Arizona.

&&

.AVIATION...Updated at 2330Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
VFR conditions will prevail through the forecast period. Winds
will remain out of the W-SW for the nxt several hrs and clouds
should continue to dissipate. Intermittent gusts up to 15-18 kts
will be possible through sunset. Otherwise, speeds should remain
aob 8 kts overnight at all terminals. The typical easterly shift
is expected to occur by 08Z at KIWA and approx 10Z at KPHX.

Southeast California/Southwest Arizona including KIPL and KBLH:
VFR conditions with clear skies are expected throughout the
forecast period. W-NW winds will be preferred at both terminals
overnight and into tomorrow morning, although some periods of
variability will be possible.

&&

.FIRE WEATHER...
Below normal temperatures will continue the next couple of days,
before a gradual warming trend takes hold the latter half of the
week. This will lead to the return of above normal temperatures by
Thursday. Occasional breezy conditions are expected mainly across
eastern high terrain areas this afternoon, where 20-25 mph gusts
remain possible. Lighter winds are anticipated beginning Tuesday
through the remainder of the week. Humidity values have shown some
improvement the past couple of days, with min RHs in the 20-30%
range this afternoon. This will decrease to 15-25% on Tuesday as
overnight recoveries range between 40-65% tonight and 30-55%
Tuesday night. Overall dry conditions will prevail this week,
before a slight increase in moisture occurs this weekend.

&&

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

$$

DISCUSSION...Hirsch
AVIATION...Salerno
FIRE WEATHER...Leffel