Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/27/21

Area Forecast Discussion

National Weather Service Phoenix AZ

 410 PM MST Fri Feb 26 2021

.UPDATE...
Updated Aviation

&&

.SYNOPSIS...
A dry weather system moving through on Sunday will bring another
round of cooler temperatures and breezy to windy conditions. High
pressure will briefly settle back into the region early next week,
before a potential weather system moves through during the middle of
next week. Temperatures next week will start off at or just above
seasonal normals before a more significant warming trend likely
takes place late next week.

&&

.DISCUSSION...
Dry northwest flow is in place across the region. A 20Z sounding
out of the Yuma Proving grounds had a PWAT of 0.10" and up to 80F
dew point depressions at the surface and in the 800-600 mb layer.
Feel like I need eye drops after looking at that! Dew points are in
the teens across south-central AZ early this afternoon. The dry
conditions aided in another cool start to the day. ACARS aircraft
soundings shows temperatures a few degrees warmer in the 850-700 mb
layer compared to yesterday, so generally expect afternoon highs to
top out a few degrees warmer as well, in the low to mid 70s across
the lower deserts.

Similar temperatures are expected again Saturday as the region
maintains dry northwest flow aloft at the base of a trough moving
into the Great Basin/Intermountain West. The leading shortwave
within the broader trough will likely lead to breezy north winds
along the Lower Colorado River Valley Saturday afternoon with a weak
dry cold front pushing south. A second shortwave is expected to
follow on the heels late Saturday into Sunday. Models remain in good
agreement this second shortwave will split off from the main trough
and track southward through Arizona on Sunday. Very little moisture
will accompany this next system with the bulk of the moisture
passing through the Four Corners area. There may be a few isolated
light showers across the high terrain northeast and east of Phoenix
Sunday afternoon, but slight chance PoPs are mostly confined to the
Mogollon Rim. Temperatures will also take a decent dip Sunday with
highs likely topping out mostly in the mid 60s across the lower
deserts.

The biggest impact with Sunday`s system will again be the increase
in winds with potential advisory level winds affecting portions of
southeast California and southwest Arizona. Strongest gradient winds
look like they will occur during the morning hours Sunday, with
ridgelines like the Chocolate Mtns. seeing speeds up to 45-55 mph.
After sunrise Sunday and through the afternoon, gusts mixing to the
desert floors are favored more in the 35-45 mph. This may kick up
areas of dust and lead to elevated fire weather conditions with the
dry conditions. There is some uncertainty what winds will be seen in
south-central AZ, in particular the Valley, as there is short-range
model support for a col to develop over the Valley as the upper and
surface/low level low passes over the area. If this happens, the
Valley could be shielded from stronger wind gusts or a sharp
gradient in speeds from SW to NE Valley could set up. If not, the
Valley is likely looking at 20-25 mph wind gusts Sunday afternoon.

The weather pattern early next week will support a progressive ridge
moving through the region Monday into early Tuesday leading to a
brief warming trend and highs back in a 70-75 degree range. Models
are still showing a weather system potentially affecting our region
at some point during the middle of next week, but there are a wide
range of possible solutions. A good portion of the GEFS members show
the possibility of a closed low forming off the West Coast before
slowly tracking back to the east across our region Wednesday into
Thursday. In contrast, most of the EPS members show a quicker-moving
open wave tracking through our region. Both solutions do support
chances for precip, albeit low (15% or less for our CWA). Roughly
50% of EPS members and 1/3 of GEFs members with the 12Z runs have
measurable rain in Phoenix. Conceptually it may be tough to overcome
the dry air we have been locked into recently, which ideally favors
the high terrain north and east of Phoenix as having the best precip
chances at this point. Either way, the system is not likely to bring
much in the way of additional cooling to the region, so temperatures
will most likely hover around seasonal normals through the middle of
the week. For late next week, the ensemble cluster analysis mostly
agrees a substantial ridge is likely to move across the Southwestern
U.S. which should push our high temperatures closer to or even above
80 degrees by next Friday.

&&

.AVIATION...Updated at 2310Z.

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

No weather issues will exist through Saturday evening under clear
skies. Winds will favor typical diurnal directional trends in
Phoenix with overnight easterlies possible developing somewhat
earlier than usual. In SE California, north winds will eventually
become the predominant direction and may occasionally become gusty
Saturday afternoon.

&&

.FIRE WEATHER...
Sunday through Thursday:
Dry conditions are likely to prevail through much if not the entire
period, despite a weak weather system and another one during the
middle of next week potentially affecting the region. The first
weather system coming through on Sunday will be dry, but it will
lead to an increase in winds with gusts to around 30-40 mph across
southeast California and southwest Arizona. This may lead to a
period of critical fire weather conditions Sunday afternoon,
particularly across the Lower CO River Valley. The dry air mass in
place will lead to day to day minimum humidities down to around 10%
most days. After a brief respite early next week, another weather
system will be possible around Wednesday, but precipitation chances
remain somewhat low. Temperatures through the period will stay
fairly close to seasonal normals with a substantial warming trend
possible late next week.

&&

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

&&

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

&&

$$

DISCUSSION...Benedict/Kuhlman
AVIATION...MO
FIRE WEATHER...Kuhlman