Heavy Rain in California, August 31, 2016

Name: Heavy Rain in California, August 31, 2016
Start: 2016-08-31T14:50
End: 2016-08-31T16:45
Location: California

August 31, 2016 · NWS PSR · 1 event in 1 county or zone

Where it happened

Every event with a place to put it. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

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The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 1

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.

What happened

The episode as NWS PSR wrote it up.

Thunderstorms developed across portions of eastern Riverside County, to the southeast of Joshua Tree National Park, during the afternoon hours on August 31st. Some of the storms produced locally heavy rainfall that was sufficient to cause episodes of flooding near the town of Desert Center. Trained spotters reported several inches of runoff flowing across Kaiser Road near Highway 177 in Desert Center. The flowing water was below flash flood criteria but sufficient to cause very hazardous conditions for motorists attempting to drive on Kaiser Road. No accidents or injuries were reported as a result of the street flooding.

What forecasters said that day

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 Aug 31, 1:20 PM PST, 1 hour 30 minutes earlier.

Area forecast discussion, Aug 31, 1:20 PM PST, 1 hour 30 minutes before

Area Forecast Discussion
National Weather Service Phoenix AZ
220 PM MST WED AUG 31 2016

.SYNOPSIS...
Deeper monsoon moisture returned to central and southeast Arizona on
Tuesday, enough for a threat of showers and thunderstorms overnight
from Phoenix east and south. A slight chance of afternoon and
evening showers and thunderstorms in central and eastern Arizona
will continued on Thursday. A drier and stable airmass will return
to the region Friday through early next week.

&&

.DISCUSSION...

Tonight and Thursday...

A weak inverted trof from northwest Mexico is still forecast to move
and develop toward the Mexican border southwest of Tucson. With
monsoon moisture in place, a few thunderstorms, some strong, are
expected. The thinking was that northward moving outflow boundaries
could possibly push across northern Pinal and Maricopa counties this
evening. Some with blowing dust.

At 2 pm only isolated storms were noted just southwest of Tucson,
however the disturbance wasn't expected to develop fully at this time.

Additionally, models show that if thunderstorms develop southwest of
Tucson, the northward moving Mexican trof could spread considerable
debris clouds north toward Phoenix overnight for a slight chance of
nocturnal showers.

On Thursday, models forecast even more monsoon moisture, and as the
former Mexican disturbance moves out of southeast AZ and into
southern New Mexico, upper level westerly winds become slightly
difluent from Phoenix eastward. This combined with afternoon
thermodynamics, will result in a slight chance of afternoon and
evening showers and thunderstorms, mostly in south central AZ
including Phoenix.

Friday...monsoon moisture is forecast to thin during the afternoon,
and with much warmer air aloft, any thermodynamically generated
storm activity will favor the mountains east of Phoenix.

Saturday through Wednesday...a dry and stable airmass will spread
into the region from the west. Afternoon temperatures will be near
normal with nearly cloudless skies. No storm activity is expected.

&&

.AVIATION...

South-Central Arizona Including KPHX, KIWA, and KSDL:

Anticipate thunderstorms to struggle to survive over the Valley
floor this afternoon and evening. However, isolated storms are quite
possible near the foothills as well as Pinal County. However,
thunderstorm outflow winds should be expected to affect metro area
TAF sites (including KPHX) during the 23Z-04Z time frame. The most
likely scenario is for relatively weak outflow to move in from the
northeast (mainly affecting KSDL, KDVT) followed by stronger outflow
moving across Pinal County northeastward into metro Phoenix after
02Z (possibly as late as 04Z). The latter will likely have blowing
dust with it. Too early as of this writing to say how low the vsbys
will go - need to see how storms develop first. Overnight,
anticipate some debris clouds (AOA FL100) and isolated weak showers.
Otherwise, surface winds will favor easterly component the rest of
the afternoon and night.

Southeast California/Southwest Arizona including KIPL and KBLH:

Skies will remain clear except perhaps for some scattered debris
clouds AOA FL150. Winds will favor south and southeast directions
the rest of the day and overnight (except perhaps areas close to
high terrain). Another outflow related Gulf surge is possible after
12Z...mainly affecting the Lower Colorado River Valley.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...

Friday through Tuesday:

Southwesterly flow will mainly confine thunderstorm activity to the
higher terrain of northern and eastern Arizona Friday. A drying
trend will then take place Saturday through Monday as a series of
low pressure systems move through the Intermountain West. Breezy
conditions are also expected during the afternoon Saturday and
Sunday across much of the area, however critical thresholds are not
expected to be reached. Moisture values will likely trend upward
again by next Tuesday, though conditions will still remain
unfavorable for thunderstorms.

&&

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

&&

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

Visit us on Facebook...Twitter...and at weather.gov/phoenix

DISCUSSION...Vasquez
AVIATION...AJ
FIRE WEATHER...Hirsch

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

1 heavy rain. Local standard time, as filed.

Heavy Rain, Riverside

When: August 31, 2:50 PM PST to 4:45 PM PST
Where: Riverside County, 0.69 mi S of Desert Center
Reported by: Trained Spotter
Coordinates: 33.710, -115.400

Thunderstorms developed across portions of eastern Riverside County, to the southeast of Joshua Tree National Park, during the afternoon hours on August 31st. Some of the stronger storms produced locally heavy rainfall sufficient to cause episodes of street flooding near the town of Desert Center. At 1525PST, a trained weather spotter in Desert Center reported 4 to 5 inches of water flowing across Kaiser Road near Highway177 in Desert Center. The flooding was not serious enough to be considered flash flooding but did produce hazardous driving conditions for motorists on Kaiser Road. The spotter measured about one quarter of an inch of rain within a 15 minute period. A Small Stream Flood Advisory was issued for the Desert Center vicinity as a result of the locally heavy rain and the street flooding.

What these are

Heavy Rain: Rainfall totals unusual for the place and season that did not produce a flood.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in California in 2016 Every state in 2016 This day in weather history Warnings in California, August 2016

Sources

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 2026-09-24. Each event’s entry at NCEI: 648247.