Arizona, 2017

Flash Flood in Arizona, February 28, 2017

February 28, 2017 · NWS PSR · 1 event in 1 county or zone

A large Pacific low pressure system brought considerable moisture to the central deserts on February 28th, and as a result there was considerable urban and small stream flooding as well as numerous flowing washes. This resulted in the need for multiple hydrologic products such as flood advisories and flood warnings.

Where it happened

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

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  • Floods
  • Wind
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  • Heat and drought
  • Cold
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The toll

Deaths
0
Injuries
0
Property damage
$20,000
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.

A large Pacific low pressure system brought considerable moisture to the central deserts on February 28th, and as a result there was considerable urban and small stream flooding as well as numerous flowing washes. This resulted in the need for multiple hydrologic products such as flood advisories and flood warnings. In addition, flash flooding was reported on the west side of Phoenix during the evening hours, near Interstate 10. A swift water rescue was needed as a result of the sudden rise in water near the Hassayampa river near Tonopah.

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 Feb 28, 3:20 PM MST, 2 hours 40 minutes earlier.

Area forecast discussion, Feb 28, 3:20 PM MST, 2 hours 40 minutes before
Area Forecast Discussion
National Weather Service Phoenix AZ
320 PM MST Tue Feb 28 2017

.SYNOPSIS...
Dry conditions can be expected tonight except for a lingering
slight chance of showers early this evening over higher terrain
areas east of Phoenix. Dry conditions and much warmer
temperatures will return for the latter half of the week and the
coming weekend.

&&

.DISCUSSION...
Showers and thunderstorms have declined quite bit with just some
isolated showers over our higher terrain forecast zone east of
metro Phoenix (a bit more numerous over WFO TWC's CWA incl. SE
Pinal and western Graham Counties). The downtrend is due to the
forcing shifting eastward as well as the start of dry advection.
The latter is quite evident further west with dew points over the
Lower Colorado River Valley running 10-20 degrees lower than 24
hours ago. Water is still running in some of the larger washes of
northern Maricopa County and Gila County including the Agua Fria
River, Cave Creek, the Hassayampa River, and Tonto Creek. Of
those: Cave Creek is trending down sharply; the Agua Fria (which
hit Moderate Flood stage at Rock Springs) and the Hassayampa in
Wickenburg are starting to trend down; and the Tonto is just now
leveling off. Will let the warnings continue for now with the
thinking being that there will still be enough flow for a while to
make unbridged crossings impassable within the warning boxes
(especially on Tonto Creek).

Heights, thicknesses trend sharply upward tonight. Given the clear
skies, radiative cooling could help generate some fog but expect
this will be largely offset by the decreasing dew points and some
lingering mixing as a northerly gradient starts to tighten.
Wouldn't be surprised to see some local visibilities down to 5-6
miles but not bad enough to mention fog in the forecast.

UL heights and flow aloft will moderate as high pressure builds
over the West, but a still invigorated sub-tropical jet to our
south will lag trough heights across portions of the Southwest for
the end of the week. The large-scale pattern will remain very
active across the Pacific Northwest and Great Basin, which will
largely keep ML heights suppressed through early next week. Drier
flow off the Pacific will keep our skies mostly clear and once
ridging takes hold of the area and increases thicknesses,
temperatures will undergo a healthy warming trend for the late
week and weekend. Temperatures are likely to reach the low-80s
across many locales for the first weekend of March in the
Southwest. Substantial moisture will be hard-pressed to return to
our area, keeping rain chances near or at zero through the
extended forecast period and possibly beyond.

&&

.AVIATION... South-Central Arizona including KPHX, KIWA,and KSDL:

The rain showers have departed the area to the east leaving mostly
SCT low clouds from 4-9Kft with only short periods of BKN cigs near
6Kft. expected til 23Z. Very breezy westerly winds with gusts of 20-
22 kt. will continue until early evening. Tonight expect light
diurnal winds and mostly clear skies.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

Expect mostly clear skies with occasionally breezy westerly and
northerly component winds with gusts of 16-18 kt. during the
afternoon. Diurnal winds should taper off during the evening to
about 5-10 kt.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Thursday through Monday...Dry west to southwesterly flow aloft with
a strong warming trend. Lower desert afternoon temperatures are
foreast to be in the lower 80s this weekend and Monday. Minimum
relative humidity in the 15 to 20 percent range. North to northeast
surface wind 8 to 12 mph Thursday and Friday, becoming light and
variable under 10 mph this weekend. Good overnight recovery.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter reports will not be needed through the weekend.

&&

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

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

DISCUSSION...AJ/Nolte
AVIATION...Sawtelle
FIRE WEATHER...Vasquez

In the hours before

Local storm report, Feb 28, 12:10 PM MST, 5 hours 50 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
1210 PM MST TUE FEB 28 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1200 PM     HAIL             4 W EAST MESA           33.41N 111.75W
02/28/2017  U0.25 INCH       MARICOPA           AZ   TRAINED SPOTTER

            .

&&

PI
Local storm report, Feb 28, 12:19 PM MST, 5 hours 41 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
1219 PM MST TUE FEB 28 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1206 PM     HAIL             3 NW NORTH SCOTTSDALE   33.66N 111.93W
02/28/2017  E0.50 INCH       MARICOPA           AZ   TRAINED SPOTTER

            .

&&

PI
Local storm report, Feb 28, 12:22 PM MST, 5 hours 38 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
1222 PM MST TUE FEB 28 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1215 PM     HAIL             1 N PHOENIX             33.46N 112.07W
02/28/2017  E0.50 INCH       MARICOPA           AZ   PUBLIC

            .

&&

PI
Local storm report, Feb 28, 12:25 PM MST, 5 hours 35 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
1225 PM MST TUE FEB 28 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1220 PM     HAIL             4 W APACHE JUNCTION     33.41N 111.61W
02/28/2017  E0.50 INCH       MARICOPA           AZ   TRAINED SPOTTER

            .

&&

PI/RT
Local storm report, Feb 28, 12:30 PM MST, 5 hours 30 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
1230 PM MST TUE FEB 28 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1227 PM     HAIL             2 ESE SCOTTSDALE        33.48N 111.89W
02/28/2017  E0.25 INCH       MARICOPA           AZ   TRAINED SPOTTER

            .

&&

PI
Local storm report, Feb 28, 12:33 PM MST, 5 hours 27 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
1233 PM MST TUE FEB 28 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1231 PM     HAIL             2 NNW ARIZONA STATE UNI 33.45N 111.95W
02/28/2017  U0.25 INCH       MARICOPA           AZ   NWS EMPLOYEE

            .

&&

PI

The radar

The Phoenix radar (KIWA), 113 km away, was scanning. The volume nearest the first event began at 01:01 UTC.

Open the radar archive at this moment

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Maricopa

When
February 28, 6:00 PM MST to 10:00 PM MST
Where
Maricopa County, 1.85 mi N of Wintersburg to 4.05 mi ENE of Tonopah
Cause
Heavy Rain
Property damage
$20,000
Reported by
Broadcast Media
Coordinates
33.447, -112.875

A wet Pacific storm system moving through Arizona led to urban and small stream flooding in the greater Phoenix area on February 28th and caused many area washes and rivers to flow. As a result, flash flooding was observed on the west side of Phoenix near the community of Tonopah and along Interstate 10. According to local broadcast media, at 2100MST a swift water rescue of a man trapped in a vehicle occurred near Tonopah. A nearby Hassayampa river gauge with roughly zero flow jumped to 800 cubic feet per second in a matter of minutes with a flow depth of 2.5 feet reported. The fast water trapped the man and thus the need for the water rescue.

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.

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

The same day elsewhere

More

Every storm in Arizona in 2017Every state in 2017This day in weather historyWarnings in Arizona, February 2017

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: 687645.