Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/21/23

Area Forecast Discussion

National Weather Service Phoenix AZ

 512 PM MST Sat May 20 2023

.Update... Updated Aviation

&&

.SYNOPSIS...
Drier conditions will continue to settle this weekend with chances
for showers and thunderstorms decreasing and mostly remaining over
the Arizona higher terrain. By Monday, rain chances completely
come to an end across the area. A warming trend will also be seen
this weekend with lower desert high temperatures back to around
100 degrees by Sunday, staying there through much if not all of
next week.

&&

.DISCUSSION...
Afternoon thunderstorm development is underway across the northern
Arizona high terrain this afternoon, while radar only shows a few
areas of weak reflectivity across our CWA thus far. Daytime
heating continues to aid in cumulus development across southern
Gila County and across parts of the Arizona lower deserts, such as
La Paz County, early this afternoon with a few weak showers now
popping up. A few isolated showers and thunderstorms will be
possible in the aforementioned areas this afternoon, but we will
see much less activity compared to what we saw yesterday.

The upper level low that`s been stationed over the Baja Peninsula
this week continues to advance northward in Arizona. After dealing
with anomalous amounts of moisture for the typically dry month of
May, which has led to daily showers/thunderstorms across the
region, drier air is now working its way into the region thanks
to dry southerly flow with the northward advancing low. Phoenix
ACARS soundings show PWAT values have fallen to around 0.90"
compared to values around 1.20" yesterday. The loss in moisture as
well as dynamic support will result in much less robust
convection for this afternoon. Adequate instability with MUCAPE to
around 500 J/kg will at least promote isolated thunderstorm
development along orographic features across southern Gila County
as well as the Kofas in southwest Arizona. The 12Z HREF supports
this idea and given DCAPE values will be over 1,000 J/kg, a few
strong, gusty outflows are possible, primarily across the high
terrain east of Phoenix. Probabilities for outflow winds exceeding
35 mph climb upwards of 50-70% across southern Gila County for
this afternoon. Paintball plots also support more convective
activity across Mohave County and San Bernardino County going
through the afternoon, but this activity along with any
associated strong outflows will likely remain away from our
forecast area.

Going through Sunday, the upper level low is seen exiting the region
to the northeast with the energy at the H5 level splitting, with the
stronger piece of energy exiting to the northeast and another weaker
circulation drifting back to the southwest over northern Baja. The
gradual drying trend will continue Sunday into early next week with
PWAT anomalies pushing northward out of our area according to global
ensembles. A few isolated showers/thunderstorms will be possible (<
20%) across the southern Gila County high terrain for Sunday, but
any PoPs thereafter will be focused across northern Arizona early
next week.

Going through the week next week, the synoptic weather pattern looks
to settle into a blocking pattern with a ridge setting up over the
central CONUS and nearly stationary upper level troughs along the
West Coast and over the East Coast. For our region, this will allow
for southwesterly flow aloft to set up and promote dry conditions.
Ensemble cluster analysis shows good agreement in a deep trough
setting up over the Pacific Northwest by Monday, eventually leading
to more broad troughing stretching southward along the entire U.S.
West Coast by Tuesday into Wednesday. This set up is likely to keep
our weather dry and quiet with H5 heights stable at around 580-582dm
and temperatures changing very little. The latest NBM shows high
temperatures warming up above normal for the first half of the week
with lower desert highs around 100 degrees each day. Going through
the latter part of the week, the trough to our west may have more of
an influence in allowing temperatures to drop back into the 90s
across the lower deserts, especially across southeast California and
southwest Arizona.

&&

.AVIATION...Updated at 2330Z.

South-Central Arizona including KPHX, KIWA, KSDL, KDVT:
No aviation concerns are expected during the TAF period under FEW-
SCT mid-level cloud cover. Winds are expected to begin their
return to typical diurnal tendencies, with speeds primarily aob
10 kts through the period. A few weak outflows from
distant/diminishing thunderstorms may produce periods of erratic
winds this evening and early tonight. However, confidence in
outflows impacting terminal locations at this time is low as
current guidance indicates W`rly continuing through tonight before
winds shift to the E early tomorrow morning.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns are expected during the period as tranquil
weather is expected to prevail. At both terminals, SE winds will
continue over the next few hours before a switch to the SW late
this evening. IPL will likely see a switch back to the SE early
tomorrow morning, while BLH picks up flow out of the S by mid-
morning. Other than a FEW cumulus clouds this evening and tonight,
skies look to be mostly clear for the remainder of the period.

&&

.FIRE WEATHER...
This weekend will bring drier air into the region with only a 5-10%
chance for wetting rains and a few isolated thunderstorms possible
over the higher terrain. Any thunderstorms that develop today will
have the potential to produce a few gusty, erratic outflows and
lightning. Humidities will gradually lower this weekend with Min
RHs decreasing to 15-25%. After near normal temperatures today,
high temperatures are forecast to warm to a few degrees above
normal starting Sunday. Winds will also return to more typical
diurnal trends with little to no influence from thunderstorms
going into next week. Anticipate little change thereafter with
the weather pattern keeping temperatures just above normal and
seasonably dry conditions in place next week. MinRHs will drop to
closer to 10% by the middle of next week with typical diurnal wind
patterns, daytime breeziness and gusts to around 20 mph most
days.

&&

.HYDROLOGY...Updated 330 PM MST 5/19/2023

GILA: Ongoing releases from Painted Rock Dam continue to travel down
the Gila River through Yuma County. These releases will continue to
impact unbridged crossings with multiple roads reportedly closed due
to flooding. The latest USGS gauge observation along the Gila River
near Dateland reported a depth of 8.1 feet, which is just above
action stage (8 feet). Further downstream, another USGS gauge near
Dome, north of Yuma, shows a near 22 feet, which is above action
stage (20 feet). Flood Warnings in effect along the Gila River
between Painted Rock Dam and the Colorado River have been extended
out through at least May 30th.

&&

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

$$

DISCUSSION...Smith/Kuhlman
AVIATION...RW
FIRE WEATHER...Smith/Kuhlman
HYDROLOGY...Benedict/Smith