A deep trough with a very strong jet streak produced gradient wind gusts at the surface up to 50-55 mph. The strong winds generated widespread blowing dust across Southeast California.
Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS PSR wrote it up.
A deep trough with a very strong jet streak produced gradient wind gusts at the surface up to 50-55 mph. The strong winds generated widespread blowing dust across Southeast California. A channel of dense blowing dust was reported along Interstate-10 in eastern Riverside County in the afternoon of the 11th. The dust impeded traffic, but no accidents were reported.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Phoenix, AZ wrote its last area forecast discussion before the first event at Oct 11, 1:10 PM PST, 1 hour 55 minutes earlier.
Area Forecast Discussion
National Weather Service Phoenix AZ
210 PM MST Mon Oct 11 2021
.SYNOPSIS...
Windy conditions will continue this afternoon and evening as a
strong low pressure system drops into the Desert Southwest. There
will also be a slight chance of a shower this evening just ahead
of a cold front. Exceptionally cool conditions will arrive Tuesday
with high temperatures struggling to even reach the 70 degree
mark across the Arizona lower deserts. A gradual warmup will begin
in the middle of the week with temperatures warming back to near
normal for next weekend.
&&
.DISCUSSION...
The low pressure system responsible for the windy conditions
continues to plunge southward through the Sierra Nevada of central
California. The well-defined vort max evident on water vapor will
blast through southeastern California this afternoon and winds
will then increase in response to a tightening pressure gradient.
Latest visible satellite imagery already reveals areas of blowing
dust near the Salton Sea. The dust is expected to expand rapidly
eastward this afternoon and this evening, and a Blowing Dust
Advisory has been issued for the lower deserts.
Latest deterministic models continue to trend even stronger with
the wind fields 850 mb and below. Wind gusts will be maximized
later this afternoon across southeastern California, and this
evening across central Arizona just ahead of the eastward
advancing cold front. Latest forecast soundings and HREF ensemble
maxes suggest peak gusts to 55 mph will not be out of the question
across the western deserts. Peak gusts could also reach up to 45
mph in the Phoenix area, which will certainly be strong enough to
send decorations airborne. Wind gusts up to 70 will also be
possible along I-8 in extreme southwestern Imperial County.
In addition to the wind, there will be a threat of isolated
showers later this evening, particularly across northern Maricopa
County and the higher terrain north and east of Phoenix where IVT
and orographic lift will be maximized. However, general consensus
from the CAMs indicates that any rain that develops will be light
and brief.
The strong cold advection Tuesday in the wake of the system will
be the other big story. NBM has been consistent indicating a
forecast high of only 70 degrees for Phoenix Tuesday, which
equates to more than 20 degrees below normal. There is also a 35
percent chance the high temperature will not even reach 70
degrees. Tomorrow’s high temperature is expected to be second
coolest for the date, only eclipsed by a high of 66 degrees in
1947! It may also be the coolest day this early in the season
since a high temperature of 70 degrees was observed on October
2nd, 1959!
&&
.PREVIOUS DISCUSSION...
The coldest night of the week still looks like Wed morning
(roughly the second morning after fropa). Lows on Wed morning
remain cold and plummet to the upper 40s to low 50s in Phoenix,
and even the low to mid 40s in some lower desert locales. Lows
around Globe fall to the upper 30s, with the low-mid 20s likely at
Hilltop. As a result the first freeze warning of the season is
possible for parts of Gila Cty for Wed morning.
For the second half of the week Clusters favor a broad W-Central
CONUS dry trough, followed by a W CONUS ridge by Friday and a
W-Cent CONUS ridge for the weekend. This pattern sequence should
result in a slow warming trend for the second half of the week
with temperatures remaining below normal in the 70s through Thu,
and the low to mid 80s for Fri. Then by Saturday and Sunday near
normal highs in the upper 80s to around 90 degrees are supported.
&&
.AVIATION...Updated at 1749Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
After easterly winds up to 10 kts through mid morning, winds will
become a far more larger issue starting late morning through this
evening as a strong storm system approaches and moves through the
region. A period of southerly cross runway winds are likely late
morning before veering towards the SSW in the afternoon and then
the WSW in the evening. Gusts around 25 kts will be likely by late
afternoon, then closer to 30-35 kts this evening with a cold
frontal passage. The strongest wind speeds should be between 04Z
and 06Z. These elevated wind speeds may also lead to areas of patchy
blowing dust during/just after frontal passage. Lofted blowing dust
could also lead to slant-range visibility issues late tonight as
well. Although precipitation and storm chances will be better north
and east of terminals with this storm system, there is still a
slight chance (10%) that showers and isolated storms could develop
near terminals, primarily after 00Z. Winds are expected to gradually
diminish during the day on Tuesday, but remain solidly from a
westerly direction into the evening hours.
Southeast California/Southwest Arizona including KIPL and KBLH:
Clear skies with light W to SSW winds, becoming variable at times,
will continue through much of this morning. Wind speeds will
increase markedly this afternoon with gusts in excess of 25-35
kts. By the late afternoon/early evening gusts will be approaching
40 kts, and even potentially exceeding 40 kts briefly. Blowing
dust may restrict local visibilities as well as becoming lofted
and impacting slantwise visibility late afternoon/evening before
gusts begin to weaken later in the evening. Skies will primarily
remain clear through the period. Winds are expected to gradually
diminish during the day on Tuesday, but remain solidly from a
westerly or northwesterly direction into the evening hours.
&&
.FIRE WEATHER...
Wednesday through Sunday:
A gradual warming trend is expected through the period but with
highs remaining below normal through Fri, and near normal by Sat.
Winds will be mostly light and diurnal/terrain influenced.
Otherwise, afternoon min RH values will mostly fall between 11-18%
through late this week and a few percentages drier by the
weekends. Overnight recoveries reach 25-45% through the late week
will fall a little to 25-40% next weekend.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Blowing Dust Advisory until midnight MST tonight for AZZ534-
537>540-542>544-546-548-550-551-553-554-559.
Wind Advisory from 6 PM to 11 PM MST this evening for AZZ537-
540>544-546-548>551-553-555.
Wind Advisory from 7 PM this evening to 2 AM MST Tuesday for
AZZ545-547-552-556>558-560>563.
Freeze Warning from 7 PM Tuesday to 8 AM MST Wednesday for
AZZ563.
Blowing Dust Advisory until midnight MST tonight for AZZ530>533-
535-536.
Wind Advisory until 9 PM MST this evening for AZZ530>536-538-539.
Wind Advisory until 11 PM MST this evening for AZZ554-559.
CA...Blowing Dust Advisory until midnight PDT tonight for CAZ560-561-
563>570.
Wind Advisory until 9 PM PDT this evening for CAZ564-568>570.
Wind Advisory until 10 PM PDT this evening for CAZ563-565>567.
High Wind Warning until 1 AM PDT Tuesday for CAZ562.
High Wind Warning until midnight PDT tonight for CAZ560-561.
&&
DISCUSSION...Hirsch
PREVIOUS DISCUSSION...Sawtelle
AVIATION...Kuhlman/Percha
FIRE WEATHER...SawtelleThe national radar mosaic for the moment the first event began.
1 dust storm. Local standard time, as filed.
Video on social media from a broadcast meteorologist showed visibilities dropping as low a a quarter mile in blowing dust across Interstate-10, roughly 35 miles west of Blythe. Traffic was slowed due to the lowered visibilities. No accidents were reported.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2021Every state in 2021This day in weather historyWarnings in California, October 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-10-01. Each event’s entry at NCEI: 990516.