Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/18/22

Area Forecast Discussion

National Weather Service Phoenix AZ

 441 PM MST Thu Feb 17 2022

.UPDATE...
Updated Aviation discussion.

&&

.SYNOPSIS...
Mostly clear skies and warming temperatures will characterize the
weather for the next few days. Locally breezy conditions across
southeast California and the Lower Colorado River Valley will
diminish this afternoon. High temperatures will increase into the
mid to the upper 70s for the weekend. More unsettled weather is
likely starting early next week with another weather system
bringing increased winds, cooler temperatures, and a chance of
rain. Snow levels will decrease leading to a risk of high
elevation snow showers as well.

&&

.DISCUSSION...
The main trough axis has moved east with clear skies noted across
most of the forecast area. ACARS soundings reveal a substantially
drier column compared to 12-24 hrs ago as cool continental air
continues to spill in from the north. Although the negative height
anomalies with the parent trough have mostly moved east, some weak
negative height anomalies will continue to persist over the area,
slightly delaying temperature recovery today. Even so, high
temperatures will warm into the mid 60s. Meanwhile, an
anomalously strong area of high pressure will return to the
western US heading into the weekend, which should allow for
temperatures to continue to climb. The NBM temperature
percentiles show the warmest days will be Saturday and Sunday,
with a 20% chance of reaching 80 F in Phoenix, and a 50-60% chance
in Imperial.

Ensemble guidance continues to indicate that an upper level low
will pass through the southern portion of the upper level ridge
early next week. Then, as the upper level ridge breaks down,
another trough will descend from the north and merge with the
upper level low. WPC cluster analysis shows that there is near
unanimous agreement on a deep trough developing and in this
general manner, but that there is uncertainty with respect to
whether the trough will elongate more to the west or if the
trough will amplify more to the south (and into Arizona). As of
now, the split is roughly even between these two ideas and there
is no preferred solution.

If the trough ends up elongating more to the west it would not
allow upper level heights over Arizona to decline as much as the
other solution. This would still result in declining high
temperatures and breezy conditions, but probably not as
substantially. On the other hand, if the trough does dig further
south the odds for gusty winds and some precipitation will
increase. As of now, NBM shows around a 20-40% chance of rain for
much of the forecast area. For the most part, individual members
of the ensemble guidance do not show substantial precipitation,
with just a few hundredths being the most likely outcome (if rain
even occurs). Snow levels will decline substantially as well,
perhaps falling to 3500 feet or so by next Wednesday. This could
allow for a few snow showers near Joshua Tree or portions of Gila
County, but given the long lead time this is a low confidence
outcome. ECMWF EFI is already beginning to pick up on the windy
signal associated with this trough. This will be watched closely
in the days ahead.

&&

.AVIATION...Updated at 2340Z.

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

A positively tilted upper trough lying across New Mexico and
portions of Arizona will continue to weaken and shift east. Winds
in the lower troposphere will generally remain north and
northeasterly through the day Friday. At the surface, anticipate a
period of light and variable conditions late this afternoon and
early evening with west/northwesterly directions being common. By
mid to late evening, most TAF sites will favor northeast and east
directions with sustained speeds AOB 8kts. However, PHX may be an
outlier due to local terrain effects and is anticipated to have
variable directions and possible even southwest/west at times in
the overnight hours but with speeds AOB 6kts. As the inversion
breaks by 16Z-17Z, easterly winds will become common and are
expected at PHX before a slow trend to northwest by late
afternoon. Skies will be clear except for scant amounts of cirrus
Friday afternoon.


Southeast California/Southwest Arizona including KIPL and KBLH:

A positively tilted upper trough lying across New Mexico and
portions of Arizona will continue to weaken and shift east. Winds
in the lower troposphere will generally remain north through the
day Friday. At the surface, anticipate northerly winds to weaken
this evening and transition to light downvalley/drainage patterns
before light northerly resumes midday Friday. Skies will be clear
except for scant amounts of cirrus Friday afternoon.

&&

.FIRE WEATHER...
Saturday through Wednesday:
Dry conditions will prevail through at least the weekend with
temperatures slightly above normal. A slow moving weather system
will approach the region from the north early next week cooling
temperatures back to normal Monday and then below normal into the
middle part of the week as the system moves into the region. This
system will also lead to increased winds for much of the first
half of next week and may also bring precipitation chances at some
point starting Tuesday. Minimum humidities over the weekend will
drop down to around 8-12% across the lower deserts before
improving into a 20-30% by next Tuesday.

&&

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

$$

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DISCUSSION...Hodges
AVIATION...AJ
FIRE WEATHER...Kuhlman