Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/02/21

Area Forecast Discussion

National Weather Service Phoenix AZ

 405 PM MST Fri Oct 1 2021

.UPDATE...Updated Aviation Discussion.


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.SYNOPSIS...
Increasing high pressure through the weekend will support a
warming trend with near to slightly above normal highs by late
this weekend and early next week. A low pressure system moving
across the region on Tuesday will bring decent chances for showers
and thunderstorms as well as slightly cooler temperatures.

&&

DISCUSSION...
The upper air pattern shows the slowly ejecting H5 closed low
pressure system over N NM with a number of surrounding vort max`s.
This was bringing fairly dry cyclonic northwesterly flow aloft
through S-Cent AZ. METSAT imagery showed mostly clear to partly
cloudy skies with areas of mainly high terrain cu. SPC
mesoanalysis indicated only slightly elevated BL dewpoints at
925-850 mb rapidly diminishing along the far E edge of AZ. Low
SBCAPE in the same E AZ area was also on the decline as a drying
trend continued. Midday ACARS soundings confirmed general drying
as mean PW values decreased to 0.65", although with some slight
lingering moisture in the BL and lower mid levels with very dry
air and NW flow above H7. Some warming CAPS were also increasing
in the mid levels.

From this afternoon and through the rest of the weekend models agree
on the N NM low pressure system continuing to slowly eject as high
pressure builds in over the Desert southwest. Other than a tiny
outside chance of very isolated popcorn showers over the eastern
high country this afternoon, the increasing high pressure will
maintain the current warming and drying trend through very early
next week. This will also result in seasonable highs topping out
in the mid 90s by late this weekend and Monday.

For Sunday to Tuesday ensembles still favor a cut-off low pressure
system positioned just offshore from N Baja ejecting and filling as
it moves into the region on Tuesday. Some ensembles show light
accumulated QPF over the deserts with more moderate amounts over the
E AZ high terrain and E-Cent AZ. GEFS Plume QPF now exhibit a
slightly reduced ensemble mean of 0.11 storm total QPF for Phoenix,
although now showing even more pronounced model spread, of not
only storm total QPF, but also for the precipitation onset. The
main impacts for Tuesday`s system would be a risk of gusty winds,
blowing dust and localized flooding, especially across the high
terrain. The Clusters analysis for 24 hr. QPF ending Tue evening
range from dry to wet solutions, although with a wetter solution
being slightly favored.

The NBM currently favors cooler temperature with Tuesday`s system
with below normal highs topping out in the upper 80s. Although
considerable uncertainty remains even for these temperatures. For
instance, the total NBM model spread for Tuesday`s high currently
ranges from 79 degrees on the low end, to 99 degrees on the upper
end.

&&

.AVIATION...Updated at 2305Z.

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

Winds across the metro area are light and variable, favoring the
north to northwest at times. Easterly wind will resume by midnight
and continue through much of the day Saturday, but remain very
weak. Skies will be mostly clear through Saturday morning, with
increasing clouds above 15 kft during the daytime hours.

Southeast California/Southwest Arizona including KIPL and KBLH:

Very light winds continue across the area. At KIPL winds will
favor the west to northwest. At KBLH northwest wind will shift to
northeast Saturday morning. Cloud cover at and above 15 kft will
increase overnight and through the day Saturday.

&&

.FIRE WEATHER...
Sunday through Thursday:
Above normal temperatures expected Sunday and Monday, with a
cooldown occurring Tuesday. Afternoon humidity levels will
increase from the 10-30% range Monday to 20-40% Tuesday through
Thursday. Overnight humidity values will also increase from 40-60%
Monday to 50-90% Wednesday. Tuesday will see a 10-30% chance of
wetting rain, mainly from Phoenix and areas north/east. Winds will
mostly be light and follow typical diurnal tendencies, however may
become locally gusty late next week.

&&

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

&&

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

$$

DISCUSSION...Sawtelle
AVIATION...Hodges
FIRE WEATHER...Iniguez