Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/29/23

Area Forecast Discussion

National Weather Service Phoenix AZ

 347 PM MST Tue Mar 28 2023

.UPDATE...
Updated Aviation Discussion...

&&

.SYNOPSIS...
Quiet conditions continue across the Southwest tonight. Warm,
mostly sunny weather is once again expected Wednesday. As a low
pressure system dives into the Southwest, gusty winds are expected
Wednesday afternoon and evening across Southeast California. By
Thursday, a few light rain showers are possible across Arizona,
along with some stronger breezes and cooler temperatures. Warmer
temperatures quickly return this weekend with low 80s expected.

&&

.DISCUSSION...
Pretty nice weather out there on this Tuesday. Other than some
cirrus, mostly sunny skies and warmer temperatures prevail. Weak
ridging is moving overhead now through Wednesday, leading to just
enough WAA to get our readings back close to normal across the
region. ACARS soundings show the Phoenix area H85 T held steady
overnight around +11C. If we get there today/tomorrow, this would
only be the 4th & 5th days we have reached 80 degrees this year
at Phoenix.

A powerful low pressure system currently sits well offshore of
Eureka, CA. At H5, the GFS initialized the low at nearly -3 SD.
Over the next 24 hours, significant wind/precipitation and related
impacts will again slide through much of CA from north to south.
Per usual, our SE Cali communities will be largely sheltered from
the precipitation, but not from potential gusty winds.

As the low progresses southeastward the next 48 hours, it will
begin to open into a deep trough over the Southwest. Initial
response will be an increase in the low/mid level wind field -
which is forecast by all models on Wednesday, extending from the
San Diego Mtns across the Colorado Desert. Expecting to mix down
some of these stronger W/SW gusts across our SE Cali zones
Wednesday afternoon and evening, so we have coordinated a wind
advisory in this area. Taking a conservative approach, even the
zone of NBM 25th percentile max gusts >40 mph is fairly sizable
late tomorrow.

Gusty winds (15-25, occasionally up to 35 mph) will continue into
Thursday across much of the CWA as the trough marches east across
Arizona. As has been mentioned previously, there is not a ton of
moisture to work with for this system, so rain chances are very
meager. In fact, the chance of measurable rain, according to the
NBM in Phoenix, has dropped to around 10%. Nonetheless, there
could be a few showers across SC Arizona on the initial front
Thursday morning/early afternoon - then once again Thursday
evening as a lagging vort max passes overhead. Continued to carry
slight chance PoPs through the metro to account for this.

Cold air advection will accompany the trough on Thursday, holding
our high temps in the 60s across many lower desert locales. Mid-
level heights will rapidly rise back to near seasonable values
from Friday into the weekend, which will allow a warming trend to
commence. By Saturday through Monday, the NBM shows good
confidence in upper 70s to mid 80s returning to Phoenix and points
westward.

Ensemble clusters are in strong agreement that the zonal flow
will be replaced by a broad trough across the West by next Tuesday
or Wednesday. The details are very murky, as one would expect,
with quite a bit of spread in strength and positioning of this
next trough. To some extent, cooler temperatures should return by
the middle of next week. Rain chances within this pattern change
are an even tougher call, but it doesn`t look like an overly
promising setup at this point in time.

&&

.AVIATION...Updated at 2246Z.

South-central Arizona including KPHX, KIWA, KSDL, KDVT,and
Southeast California/Southwest Arizona including KIPL and KBLH:

Moderate Wly/SWly flow aloft (AOA FL100) will strengthen tonight
and Wednesday as a low pressure system and associated cold front
approach the region. At the surface, SW/Wly wind directions will
be favored this evening with speeds less than 10kts (a little more
at KIPL). Nocturnal downvalley/drainage patterns will develop
during the 04Z-07Z time frame (continuing westerly at KIPL). Over
the Phoenix area during the late morning and early afternoon
Wednesday, a period of southerly winds will be favored before
southwesterly takes hold by mid afternoon with gusts of 15-20kts.
Over southeast CA, SW/Wly directions will develop after 17Z and
strengthen during the day with gusts of 25-30kts common in the
afternoon (occasionally 30-35kts). There may also be channels of
blowing dust that could possibly reduce visibilities at the TAF
sites but most likely not below 6SM. As for sky cover, only minor
cirrus is expected until some cumulus develops in the late
afternoon (SE CA).


&&

.FIRE WEATHER...
A gusty easterly component is expected to increase across the
high terrain of southern Gila County this morning, with gusts in
excess of 30 mph primarily along ridgetops, before subsiding this
afternoon. A weather system during the Wednesday/Thursday
timeframe will bring cooler temperatures, strong winds, and some
precipitation chances. Any rainfall looks to remain minimal. Winds
are expected to be strongest across southeast California. Once
this weather system exits, temperatures will return closer to near
normal readings by the weekend.

&&

.HYDROLOGY... 900 AM MST 3/28/2023
Verde/Lower Salt: Dam releases from Bartlett Dam on the Verde,
Granite Reef Dam on the Salt, and Tempe Town Lake continue to
remain steady. Despite lower flow rates, recreation areas along
the Verde and Salt rivers may still be dangerous due to elevated
water levels, erratic currents, and debris carried from upstream.
In addition, numerous closures of roads built into the river
channel continue around Metro Phoenix.

Gila: Water levels are still increasing behind Painted Rock Dam
due to upstream dam releases on the Salt River. These stages
continue to necessitate water releases from Painted Rock Dam that
may result in downstream lowland flooding. Flow through the dam
outlet continues to increase and is now exceeding 1000cfs,
according to USGS data. Along the Maricopa county portion of the
Gila, flooding would primarily affect farmland and unimproved
roads. Aerial satellite imagery from Sun 3/26 (48 hours ago)
showed a borrow pit filling downstream of the dam, with little to
no flow downstream. CBRFC indicates some flow could reach Dateland
late this week, though timing and impacts are very uncertain.

Flood statements have been sent. All of these flood warnings are
set to expire Friday, but extensions are expected as long as
anomalous streamflow persists.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Wind Advisory from noon Wednesday to 2 AM PDT Thursday for
     CAZ560-563>568.

     Wind Advisory from noon Wednesday to 5 PM PDT Thursday for
     CAZ562.

     Wind Advisory from noon to 8 PM PDT Wednesday for CAZ561-570.

&&

$$

DISCUSSION...Heil
AVIATION...AJ
FIRE WEATHER...Smith
HYDROLOGY...Heil