Flash Flooding and Heavy Rain in Arizona, August 5, 2016

Name: Flash Flooding and Heavy Rain in Arizona, August 5, 2016
Start: 2016-08-05T08:30
End: 2016-08-05T11:15
Location: Arizona

August 5, 2016 · NWS PSR · 4 events 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: $50,000
Crop damage: None recorded
Events: 4

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.

Scattered to numerous thunderstorms developed across the greater Phoenix metropolitan area during the morning hours on August 5th and due to high levels of moisture in the atmosphere, the storms quickly generated very heavy rains. Some of the heaviest rains affected the northeastern portion of the greater Phoenix area including communities such as Paradise Valley, Carefree, Cave Creek and Scottsdale. A variety of mesonet weather stations recorded morning rainfall totals ranging from 1.5 inches to over 2.6 inches, and the excessive rain led to episodes of flooding and flash flooding. A number of roads were closed due to flooding and in one case a U-Haul truck was stuck in flood waters. Flash Flood and Areal Flood Warnings were issued due to the heavy rains.

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 5, 5:59 AM MST, 2 hours 31 minutes earlier.

Area forecast discussion, Aug 5, 5:59 AM MST, 2 hours 31 minutes before

Area Forecast Discussion
National Weather Service Phoenix AZ
559 AM MST FRI AUG 5 2016

.UPDATE...Latest Phoenix sounding registered a PWAT of 2.0 inches,
nearly a record for the day. Convection has gotten off to an early
start across the Phoenix metro area and the forecast has been
adjusted to account for these trends. Scattered activity will persist
across mainly Maricopa County this morning, before spreading eastward
this afternoon.

&&

.SYNOPSIS...
A transition to drier conditions is underway, but isolated showers
and thunderstorms will still be possible today across much of
northern and eastern Arizona, including the Phoenix area. Conditions
this weekend into the first half of next week will remain mostly dry
with very limited thunderstorm activity and above normal
temperatures. A return to a more active monsoon pattern is possible
by the middle of next week.

&&

.DISCUSSION...
Latest streamline analysis shows a mid-level trough extending from
California southward into the northern Baja. WV imagery also shows
that much drier air associated with this trough continues to move
steadily eastward. Despite the drying trend, latest consensus among
the hi-res CAMs is that moisture remains sufficient for at least
scattered thunderstorms to develop across the higher terrain east of
Phoenix this afternoon. A few of the WRFs also hint at the
possibility of isolated storms across the lower deserts including the
Phoenix metro area and the latest PoPs were weighted towards the
SREF, which is an increase from the previous official forecast.
Classic inverted-V model soundings also suggest that any storms that
do develop will have the potential to produce heavy rain and strong
wind gusts.

Models remain consistent through early next week, depicting a
gradual drying trend as the southwesterly flow ahead of successive
Pacific Northwest troughs scours out the moisture across the Desert
Southwest. This anomalous pattern also means that heights/thickness
will remain in check, yielding temperatures near or slightly above
average, but certainly well below daily records. The warmest day
appears to be Monday with high temperatures approaching 110 degrees
in Phoenix. Latest GEFS reforecast PoPs indicate the threat for
storms and precipitation will take a hiatus beginning Saturday across
much of the area. Only exception will be across eastern Arizona,
where isolated to scattered thunderstorms will persist in the
vicinity of richer 1000-700 mb mixing ratios.

Models continue to indicate that deeper moisture (perhaps aided by
the mid-level remnants of TC Earl) from the sub-tropics will return
to the area by the middle of next week. Although there are distinct
differences in the magnitude of the moisture, nearly all operational
models and ensemble output show this trend through Friday. The mean
southwesterly flow is also expected to persist, suggesting that
storms will be favored again across at least southeastern Arizona.
Main impact across south-central Arizona may initially be blowing
dust.

&&

.AVIATION...
South-Central Arizona Including KPHX, KIWA, and KSDL:
Enough moisture lingers across the area to not only allow for BKN to
OVC clouds this morning but isolated light rain shower development
within some of these clouds. Added VCSH mention through 5/18z for the
Phoenix area terminals. AM winds to follow typical easterly
directions. By the afternoon, sfc winds may struggle to realize the
switch to west, developing more into southerly winds. Hi-res models
indicate some isolated thunder activity is possible throughout the
Phoenix area today, so hedged initially with VCSH until the day crew
can get a look at the morning model runs.

Chances of showers/storms in the vicinity of the terminals: 30%
Chances of outflow/erratic wind shifts: 45%

More noticeable drying will begin through the weekend, bringing a
stormy week-long period to a close and relegating storms to the
mountains and for even a brief period out of the state by early next
week.

Southeast California/Southwest Arizona including KIPL and KBLH:
Some cloudiness may enter the airspace around KBLH, otherwise
westerly flow aloft transitioning into the area should keep mostly
clear skies for the terminals today. Light morning winds will give
way to southerly directions for KBLH and southeasterly for KIPL in
the afternoon.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Sunday through Thursday...
Drier westerly flow aloft will push monsoon moisture into eastern AZ
with only a slight chance of afternoon thunderstorms over the higher
terrain of southern Gila County through Tuesday. Accordingly,
minimum humidities continue to decline as well. Overnight recovery
will be fair. Humidities trend upward Wednesday and Thursday and
storm chances return to the lower deserts of Arizona. Winds will
favor familiar diurnal patterns.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected at this time.

&&

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

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

DISCUSSION...Hirsch
AVIATION...Nolte
FIRE WEATHER...AJ

The radar

The Phoenix radar (KIWA), 45 km away, was scanning. The volume nearest the first event began at 15:31 UTC.

Open the radar archive at this moment

Event by event

3 flash flood, 1 heavy rain. Local standard time, as filed.

Flash Flood, Maricopa

When: August 5, 8:30 AM MST to 11:15 AM MST
Where: Maricopa County, 1.81 mi W of Scottsdale Muni to 4.26 mi ESE of Scottsdale Muni
Cause: Heavy Rain
Property damage: $20,000
Reported by: Trained Spotter
Coordinates: 33.619, -111.951

Scattered thunderstorms developed across the northeast portion of the greater Phoenix metropolitan area during the morning hours on August 5th, and the stronger storms produced locally heavy rains with peak rain rates well in excess of 2 inches per hour. The heavy rain led to episodes of flash flooding over portions of north Scottsdale which resulted in a number of road closures. According to a trained weather spotter in north Scottsdale, 1 inch of rain fell in 20 minutes ending at 0931MST and this resulted road closures at Hayden Loop and Frank Lloyd Wright roadway due to flooding. In addition, the center lane of Frank Lloyd Wright road at the Scottsdale airport was flooded. Finally, the right line of Northsight Boulevard at Frank Lloyd Wright road became flooded due to the intense and heavy rains.

Heavy Rain, Maricopa

When: August 5, 8:30 AM MST to 11:00 AM MST
Where: Maricopa County, 3.52 mi ESE of Phoenix Deer Vly Arp
Reported by: Trained Spotter
Coordinates: 33.670, -112.020

Thunderstorms with locally heavy rain developed across the northeast portion of the greater Phoenix metropolitan area during the morning hours on August 5th. Some of the heaviest rain fell across portions of north Scottsdale and areas east of Deer Valley. A mesonet station 5 miles east of Deer Valley measured 1.54 inches of rain as a storm total ending at 1100MST. Earlier in the same area, a trained weather spotter reported curb-to-curb flooding located about one quarter mile south of the intersection of Cave Creek Road and Union Hills Road. The flooding occurred at 0906MST.

Flash Flood, Maricopa

When: August 5, 8:30 AM MST to 11:15 AM MST
Where: Maricopa County, 0.74 mi WSW of Cactus to 1.12 mi SW of Cactus
Cause: Heavy Rain
Property damage: $30,000
Reported by: Broadcast Media
Coordinates: 33.575, -112.061

Thunderstorms with very heavy rain developed across the northeastern portion of the greater Phoenix metropolitan area during the morning hours on August 5th; some of the stronger storms produced peak rain rates in excess of 2 inches per hour. Very heavy rain and flash flooding occurred 7 miles southeast of Deer Valley and to the northeast of Phoenix Mountain Park. At 0930MST local broadcast media reported flash flooding which resulted in one car being stuck in flood waters near Cave Creek and Hatcher Roads. One person needed to be rescued from the stranded automobile. A Flash Flood Warning was issued for the area at 0930MST and the warning remained in effect through 1115MST.

Flash Flood, Maricopa

When: August 5, 9:00 AM MST to 11:15 AM MST
Where: Maricopa County, 5.28 mi N of Scottsdale Muni to 6.49 mi NNE of Scottsdale Muni
Cause: Heavy Rain
Reported by: Broadcast Media
Coordinates: 33.696, -111.925

Thunderstorms with very heavy rains developed across the far northeast portion of the greater Phoenix metropolitan area during the morning hours on August 5th. Some of the heaviest rains occurred in communities such as north Scottsdale and Paradise Valley. As of 1000MST, multiple mesonet weather stations measured storm totals of 1.5 inches or more in the area; one station near Desert Highlands Golf Club measured at total of 1.54 inches. The heavy rains led to episodes of flash flooding which resulted in road closures and vehicles trapped in flood waters. At 1000MST local broadcast media reported a U-Haul truck stuck in flood waters 6 miles north of north Scottsdale, near the intersection of North Scottsdale Road and East Happy Valley Road. At the same time another broadcast media reported roads closed due to flash flooding 7 miles south of Carefree, near the intersection of East Jomax and North Pima roads. No injuries were reported due to the flash flooding. A Flash Flood Warning was issued for the area beginning at 0920MST and it remained in effect through 1115MST.

What these are

Flash Flood: Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.
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 Arizona in 2016 Every state in 2016 This day in weather history Warnings in Arizona, 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: 647017, 647018, 647036, 647021.