Flash Flood in Arizona, August 13, 2017

Name: Flash Flood in Arizona, August 13, 2017
Start: 2017-08-13T04:00
End: 2017-08-13T07:00
Location: Arizona

August 13, 2017 · 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.

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Cold
Fire, smoke and dust
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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.

Scattered thunderstorms developed across the central deserts during the morning hours on August 13th, and some of the stronger storms affected the area around the community of Casa Grande. The storms produced locally heavy rainfall and with peak rain rates over one inch per hour, the rains were sufficient to cause episodes of flash flooding. Flash flooding was not especially significant or widespread, but it did lead to flooding in the McCartney Ranch subdivision at 0600MST; the subdivision was located about 3 miles north of Casa Grande. A Flash Flood Warning was in effect at the time of the flooding. No injuries were reported.

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 13, 3:15 AM MST, 45 minutes earlier.

Area forecast discussion, Aug 13, 3:15 AM MST, 45 minutes before

Area Forecast Discussion
National Weather Service Phoenix AZ
315 AM MST Sun Aug 13 2017

.SYNOPSIS...
Sufficient moisture remains in place this weekend supporting at
least a few showers and thunderstorms across central and eastern
Arizona. On Monday, a drying trend will end storm chances across the
lower elevations with only limited chances remaining across the
higher terrain. After Tuesday and through the end of the week,
mostly clear skies and dry conditions will prevail with near normal
temperatures.

&&

.DISCUSSION...
Well, the westerlies (which are expected to bring a substantial
drying trend into the area by early this week) have thrown a
curveball weather-wise with "transition-event" type weather
affecting the area for much of last evening and into the early
morning hours today. A disturbance embedded in the westerly flow
yielded better than expected dynamics along with impressive 300mb
divergence (as seen in the SPC mesoanalysis graphics) and produced a
large MCS across south central Arizona. Widespread showers and
thunderstorms have raked the central deserts since late yesterday
evening and the storms are still firing at 3 am. We have issued
numerous flood advisories and flash flood warnings, many of which
remain in effect. Weather has simply been too active to devote much
time to the upcoming forecast, so much of it remains the same as the
previous package. Trends look unchanged, with few if any storms
expected in the area by Tuesday afternoon. With moisture still in
place across south central AZ today, despite the increasing westerly
flow there remains a decent chance for storms today into tonight and
we raised our POPs accordingly. Temps today will stay a few degrees
below seasonal normals over the central deserts due to the clouds
and showers and the effect of this morning rains over the deserts.

Tuesday through Friday look be exceptionally dry for August with
surface dewpoints falling into the 40s and PWATS in a 0.25-0.75 inch
range. Even though we dry out, temperatures will be hindered by
unusually low heights and thicknesses aloft. In fact, H5 heights
only in a 584-588dm range will be common much of the week (typical
for late September, not mid August). Thus, high temperatures near
seasonal normals (or even a few degrees below) seem very likely with
overnight lows locally dipping to a few degrees below normal due to
the drier airmass and efficient nocturnal cooling. Some moisture may
start to seep back into southern Arizona as early as Friday, but
more likely by Saturday as the flow begins to shift more out of the
south to southeast.

&&

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

Outflows from thunderstorms that have developed over the higher
terrain to the north are now moving into the greater Phoenix area at
the present time. Gusty northerly winds in the 15-25 mph range can
be expected over the next couple of hours before becoming easterly
at/just after midnight. Thunderstorms developing over the west
valley at this time could also affect the terminals between now and
midnight, thus will be including VCTS in the terminals during this
period as well. Lesser chances for SHRA/TS after midnight as well,
but confidence is still too low at this point to include anything
more than VCSH at this time. Sct-Bkn mid/high cloud decks likely to
persist into Sunday morning before some clearing in the afternoon.
At this point, shower/TS chances look to be substantially less for
Sunday afternoon/evening.

Southeast California/Southwest Arizona including KIPL and KBLH: No
Little aviation concerns over the next 24 hours as winds remain
southerly at KBLH and from the southeast at KIPL. Showers and storms
should stay well to the east of the terminals.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday:
Unusually dry air will settle over the districts during this time
frame with almost no chance of showers or thunderstorms through the
week. Unlike most mid-monsoon breaks, temperatures will stay near
the seasonal average. With the introduction of drier air, minimum
afternoon humidity levels will fall back to a 10-20% range though
overnight recovery will remain fair to good. Upslope afternoon wind
gusts will be stronger than typical monsoon season levels Tuesday
and Wednesday with the passage of a early fall-like weather
disturbance through northern Arizona.

&&

.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...CB/MO/Kuhlman
AVIATION...Percha
FIRE WEATHER...MO

In the hours before

Local storm report, Aug 12, 11:50 PM MST, 4 hours 10 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
1150 PM MST SAT AUG 12 2017

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

1033 PM     FLASH FLOOD      2 N GOODYEAR            33.46N 112.41W
08/12/2017                   MARICOPA           AZ   PUBLIC

            SOME ROADS IMPASSABLE DUE TO FLOODING NEAR
            SARIVAL & MCDOWELL. - CORRECTION ISSUED FOR
            EVENT TYPE.

&&

MP

Local storm report, Aug 12, 11:52 PM MST, 4 hours 8 minutes before

PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE PHOENIX AZ
1152 PM MST SAT AUG 12 2017

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

1040 PM     FLASH FLOOD      2 NNW GOODYEAR          33.47N 112.42W
08/12/2017                   MARICOPA           AZ   PUBLIC

            8-10 INCHES OF WATER IN THE ROADWAY. NEAR W
            ALMERIA RD AND N 160TH AVE. CORRECTION
            ISSUED FOR EVENT TYPE.

&&

MP

Local storm report, Aug 12, 11:53 PM MST, 4 hours 7 minutes before

PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE PHOENIX AZ
1153 PM MST SAT AUG 12 2017

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

1052 PM     FLASH FLOOD      3 NNW GOODYEAR          33.48N 112.42W
08/12/2017                   MARICOPA           AZ   LAW ENFORCEMENT

            ADOT REPORTS L-303 SB EXIT AT THOMAS WAS
            FLOODED. CORRECTION ISSUED FOR EVENT TYPE.

&&

MP

Local storm report, Aug 13, 1:54 AM MST, 2 hours 6 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
154 AM MST SUN AUG 13 2017

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

0111 AM     FLASH FLOOD      3 SSW GUADALUPE         33.32N 111.97W
08/13/2017                   MARICOPA           AZ   LAW ENFORCEMENT

            WATER RESCUE NEAR I-10 AND RAY RD.

&&

CK

Local storm report, Aug 13, 2:46 AM MST, 1 hour 14 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
246 AM MST SUN AUG 13 2017

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

0226 AM     FLASH FLOOD      2 ENE TOLLESON          33.46N 112.22W
08/13/2017                   MARICOPA           AZ   LAW ENFORCEMENT

            WATER RESCUE AT I-10 AND N 75TH AVE.

&&

CK

Local storm report, Aug 13, 3:23 AM MST, 37 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
323 AM MST SUN AUG 13 2017

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

0318 AM     FLASH FLOOD      1 SW GLENDALE           33.52N 112.20W
08/13/2017                   MARICOPA           AZ   LAW ENFORCEMENT

            WATER RESCUE NEAR N 67TH AVE AND W BETHANY
            HOME RD.

&&

CK

The radar

The Phoenix radar (KIWA), 39 km away, was scanning. The volume nearest the first event began at 10:57 UTC.

Open the radar archive at this moment

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Pinal

When: August 13, 4:00 AM MST to 7:00 AM MST
Where: Pinal County, 2.57 mi E of Casa Grande Arpt to 2.23 mi W of Casa Grande Arpt
Cause: Heavy Rain
Reported by: Broadcast Media
Coordinates: 32.944, -111.726

Scattered thunderstorms developed in the area around Casa Grande during the morning hours on August 13th and some of the stronger storms produced locally heavy rains with peak rain rates over one inch per hour. The intense rain led to an episode of flash flooding about 3 miles north of Casa Grande. At 0600MST, a broadcast media report from Fox 10 news indicated that there was early morning flooding in the McCartney Ranch subdivision. Images were shown of cars on the streets with water up to the middle of the car's tires. A Flash Flood Warning was in effect during the flooding; it was issued at about 0400MST and was in effect through 0700MST.

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

Every storm in Arizona in 2017 Every state in 2017 This day in weather history Warnings in Arizona, August 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: 713598.