Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 01/19/22

Area Forecast Discussion

National Weather Service Phoenix AZ

 450 PM MST Tue Jan 18 2022

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
A weak weather system will continue to move through the region
today and produce isolated light showers for a few more hours.
Dry conditions along with near to slightly above normal
temperatures will prevail during the latter half of the week. A
weather system will bring a slight chance of showers and breezy
conditions to the area over the weekend.

&&

.DISCUSSION...
The cutoff low that has resided off the coast of California for
the past several days is now moving through Arizona as an open
wave as it begins to be reabsorbed into the main flow. Water vapor
satellite imagery show the low is now over northern Arizona and
quickly moving east. Weak ascent from modest cyclonic vorticity
advection and upper level jet support is allowing for a few
showers to develop. So far these showers have been fairly meager
with most locations seeing nothing, and just a few areas seeing a
hundredth of an inch or two. ACARS soundings continue to show a
very dry airmass below 850 hPa, which is further hindering any
rain from reaching the surface. Overall, this should continue to
be the case with showers winding down over the next few hours as
the best forcing quickly heads east. This outcome is well
supported by the HREF. Skies will clear out overnight.

A second trailing shortwave will move into Arizona on Wednesday
and temporarily amplify the back half of the departing trough
resulting in reduced geopotential heights for one more day.
Overall the effects will be minimal but HREF guidance is showing a
few showers popping up in Gila County during the afternoon hours.
NBM PoPs for Gila County increase to about 20% but remain below
5% for the rest of the CWA. The upper level high will quickly
rebound behind this shortwave for Thursday with sunny skies
expected. High temperatures will rise into the low 70s with NBM
temperature probabilities showing an 80% chance of reaching 70F or
higher in Phoenix by Thursday.

The enhanced area of high pressure will be transitory, however, as
yet another developing system dives south into Arizona Friday and
Saturday. The system will strengthen and cut off from the mean
flow on approach, but due to its inland and northerly trajectory
it will be quite moisture starved. WPC cluster analysis shows that
around 40% of the ensembles take the path of the low right over
the CWA while the remaining 60% take it east. In general, clusters
show that the western solution would offer a better chance of
some precipitation, which conceptually makes sense. As of now, NBM
PoPs are around 5-10% for south-central Arizona, and even lower
for southeast California. Perhaps the bigger story with this
system will be the wind potential. A strong area of high pressure
will trail the weather system, inducing a robust northerly
gradient Saturday and Sunday. A surge of gusty wind will result
down the Colorado River and portions of southeast California. Some
breezy conditions may also occur in the foothills north and east
of Phoenix. ECWMF EFI shows values of 0.7 to 0.9, indicating a
fairly unusual event for wind speeds. Ensembles diverge beyond
this point with respect to whether an addition shortwave trough
moves through the area or if strong ridging will return.
Regardless, conditions will likely remain mostly dry with high
temperatures remaining near seasonal norms.

&&

.AVIATION...Updated 2345Z.

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

Minor weather systems will continue to move through the area.
Isolated light showers from earlier today have moved out of the
area along with a short-term decrease in cloud cover with FEW-SCT
low-mid cloud decks from 7-18 kft. Mostly light winds AOB 7 kts
following normal diurnal tendencies will continue along with
periods of light and variable winds. BKN low cloud CIGS near 6 kft
AGL will redevelop late in the evening before scattering out
during mid-late Wed morning.

Southeast California/Southwest Arizona including KIPL and KBLH:

Mostly light to occasionally moderate winds are expected through
much of the TAF period at both terminals. Winds to favor W-N
components at KIPL, with winds at KBLH staying mostly NW-N.
Partly cloudy skies with FEW V SCT low-mid and high cloud decks
tonight and Wed morning will improve to clear to mostly clear
skies by late Wed morning.

&&

.FIRE WEATHER...
Thursday through Monday:
Dry conditions and near to slightly above normal temperatures are
favored through the period. High pressure will dominate our
weather for the beginning of the period before a weather system is
expected to move into our area this weekend. As of now, this
weather system looks to remain dry across our area, though it may
result in increased breezy conditions this weekend, particularly
for areas along and west of the Lower Colorado River Valley.
Minimum RHs are expected to be around 15-30%, while maximum RHs
are expected to be in the 30-60% range for most places through the
period.

&&

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

$$


DISCUSSION...Hodges/Smith
AVIATION...Sawtelle
FIRE WEATHER...Smith