Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/25/21
Area Forecast Discussion
National Weather Service Phoenix AZ
520 PM MST Wed Mar 24 2021
.UPDATE...Updated Aviation Discussion.
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.SYNOPSIS...
Lingering light showers will affect Gila County through this
afternoon, while breezy to locally windy conditions will persist
along the Colorado River and southeastern California. The weather
pattern will likely remain unsettled into the weekend as another
slow moving weather system moves into the region starting
Thursday. This system will bring widespread windy conditions for
Thursday afternoon, along with additional chances for light
showers mainly across central and eastern Arizona. Below normal
temperatures will last through at least Friday before a warming
trend likely pushes readings above normal starting Sunday.
&&
.DISCUSSION...
Visible satellite shows clouds encircling the center of an upper level
low over northeastern Arizona. Light showers have occasionally
drifted off the Mogollon Rim into the higher terrain east of
central Phoenix all day. While most showers have been light, some
instability has allowed a few convective showers capable of
producing small hail to develop. Lightning has been nearly
nonexistent, so far, with only one or two cloud flashes detected.
For the rest of this afternoon, light to moderate showers are
anticipated to continue east of Phoenix but lingering moisture
farther west could allow a few to develop over the lower desert.
Otherwise, skies will continue to clear across the rest of the
forecast area through the rest of today and tonight.
Another embedded shortwave within broad western troughing is anticipated
to strengthen and dig into the Southwest tomorrow following a similar
trajectory as yesterday`s wave. Ensemble guidance indicates a strong
850 mb jet of 35-45 kt winds will form and stretch across the forecast
area late Thursday morning and afternoon. Meanwhile, the latest
available ECMWF EFI retains indications for strong wind potential
across a wide portion of south-central Arizona and southeast
California tomorrow. Wind speeds of 15-30 mph will be common while
gusts exceeding 40 mph are anticipated. As such, Wind Advisories
have been issued for much of the forecast area.
With these winds, blowing dust will also be a concern. While rain has
fallen in some areas since Tuesday, rainfall amounts and coverage
may not have been enough to tamper the blowing dust potential. The
areas most prone to blowing dust are Pinal County south of Phoenix
and portions of southeast California but other areas could see
isolated/scattered impacts from blowing dust. While not every location
might see reduced visibility from dust, Blowing Dust Advisories
have been issued to highlight the increased threat. Localized areas
of reduced visibility below 1/4 mile are also possible, such as
where dust channels form, depending on local landuse. If blowing
dust does occur, lofted blowing dust could linger over many areas
through tomorrow evening.
An inland trajectory of this system will keep moisture levels fairly
low, but there should be sufficient moisture for at least scattered
light showers starting Thursday evening after the passage of the
cold front across the central and eastern Arizona high terrain.
Precip chances mainly over the high terrain are likely to continue
into Friday, and possibly Saturday, if this turns into another
closed low. Given the low moisture levels, latest forecast QPF
amounts are rather low with storm totals less than 0.25" across
much the high terrain and likely little if anything over the
south-central Arizona deserts. Snow levels are likely to drop to
5500-6000 feet at times during the event, but accumulating snows
should mostly be relegated to the Mogollon Rim and the White
Mountains.
Temperatures will remain near to below normal the next few days as
tomorrow`s system reinforces a cooler airmass. Highs fluctuate between
the upper 60s/low 70s to the mid 70s through Friday before ridging
aloft supports a warming trend this weekend. If Thursday`s system
is slow to eject eastward and lingers, the warm up could be
delayed by a day or so. Nevertheless, afternoon highs have a 70%
chance of reach 80 degrees across SE CA and SW AZ by Saturday, and
98% chance of reaching 85 degrees by Monday. Farther east in the
Phoenix area, there is a 50% chance for highs reaching 80 degrees
by Saturday and 73% chance for reaching 85 degrees by Monday.
&&
.AVIATION...Updated at 0010Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Moderate westerly component winds will taper off and become light
and variable to light and a southerly component by early to mid
evening. Winds will transition to an easterly component shortly
after midnight tonight. FEW-SCT decks aoa 8 kft are expected to
dissipate early this evening. Elevated southeasterly winds mid
morning Thu to transition first to southerly during the late
morning, then to westerly in the early afternoon. Westerly winds
on Thu likely to become rather strong and gusty by mid-late
afternoon as a rather robust Pacific weather system moves into the
region.Gusts upwards of 20-30 kt are possible. These strong winds
likely to produce areas of blowing dust as well, but confidence
is still too low at this point to include BLDU at KPHX. A more
likely concern will be slant-range visibility reductions for
aircraft on approach into the terminals. BKN-OVC mid-level CIGS
likely to return as well during the day on Thu near 16-18 kft
along with isolated sprinkles and virga.
Southeast California/Southwest Arizona including KIPL and KBLH:
Winds will favor a northwest-west-southwesterly component during
the early evening, with winds at KBLH to become southerly late
tonight along with some LLWS developing Thu morning as shown in
the TAF. Westerly winds at KIPL and southerly winds at KBLH likely
to become rather strong and gusty by mid-late morning on Thu as a
rather robust Pacific weather system moves into the region. Gusts
upwards of 25-35 kt are possible. These strong winds likely to
produce areas of blowing dust as well with visibilities falling to
4-6 sm in BLDU at the sites. In addition, slant-range visibility
reductions for aircraft on approach into the terminals are
expected. BKN mid-high level CIGS likely to return as well during
the day on Thu.
&&
.FIRE WEATHER...
Saturday through Wednesday:
Winds are anticipated to follow more typical patterns with speeds
mostly at or below 10-15 mph in the afternoon. The area will
undergo a warming and drying trend with temps reaching the mid 70s
to mid 80s across the board. This will cause afternoon min RH
values to frequently drop into the 8-15% range. Overnight
recoveries will also decline a few percentages each day and
eventually settle into the 20-40% range early next week.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Blowing Dust Advisory from 11 AM to 8 PM MST Thursday for
AZZ530>540-542>544-546-548-550-551-553>555-559.
Wind Advisory from 11 AM to 8 PM MST Thursday for AZZ530>563.
CA...Blowing Dust Advisory from 11 AM to 8 PM PDT Thursday for
CAZ563>570.
Wind Advisory from 11 AM to 8 PM PDT Thursday for CAZ560-561-
563>570.
Wind Advisory from 5 AM Thursday to 5 AM PDT Friday for CAZ562.
&&
$$
DISCUSSION...AD/Khulman
AVIATION...Sawtelle/Percha
FIRE WEATHER...AD