Flash Flood in Arizona, November 29, 2019

Name: Flash Flood in Arizona, November 29, 2019
Start: 2019-11-29T05:00
End: 2019-11-29T11:00
Location: Arizona

November 29, 2019 · 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.

A powerful Pacific low pressure system moving slowly east across Arizona interacted with deep moisture to produce widespread moderate to heavy rain across south central Arizona during the morning hours on November 29th. In addition to frontal lift, isolated thunderstorms were embedded within that rain bands helping increase rain totals. The heavy rain led to some flash flooding over higher terrain areas east of Phoenix, including near the Woodbury burn scar, during the mid morning hours. Heavy rain on the burn scar resulted in a rapid 4 foot rise in Fish Creek Canyon, as reported by data from Maricopa County Flood Control stream gage. There were no reports of accidents due to the flash flooding. A Flash Flood Warning was in effect at the time of the 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 Nov 29, 3:04 AM MST, 1 hour 56 minutes earlier.

Area forecast discussion, Nov 29, 3:04 AM MST, 1 hour 56 minutes before

Area Forecast Discussion
National Weather Service Phoenix AZ
304 AM MST Fri Nov 29 2019

.SYNOPSIS...
Widespread rain will taper off from west to east this morning with
lingering shower activity this afternoon and tonight over
portions of south-central Arizona. Snow levels will drop rapidly
from west to east today and a Winter Storm Warning remains in
effect above 4500 feet over much of Arizona. Expect much cooler
high temperatures today with readings peaking the 50s on the
deserts. Warmer and drier conditions are expected during weekend
as high pressure builds across the Rockies. Another low pressure
system will bring a chance of rain to the region midweek.

&&

.DISCUSSION...
A north-south oriented cold front was located over western
Maricopa County as of this writing with a narrow band of intense
rainfall. While there is CAPE, the updrafts have been relatively
shallow and thus there has been little to no lightning. But, with
the strong environmental winds and convective mixing, cannot rule
out brief severe level gusts. There is an outside possibility of
a brief and weak non-supercell tornado embedded within the line
at any point. Meanwhile, rainfall rates have exceeded half an
inch in 30 minutes. Stream gauges and law enforcement have
reported flash flooding in various locations spanning eastern
Riverside, Imperial, La Paz, Yuma, and Maricopa Counties since
late yesterday afternoon. In addition to the frontal zone lift,
there is ongoing rainfall west of there due to QG forcing
associated with PVA and jet energy rounding the bottom of the
trough. Very strong southerly winds have accompanied the approach
of the front with peak gusts of 40-50 knots over the metro area.
Behind the front, winds have been much weaker.

Scattered showers have developed ahead of the front over northeast
Maricopa (including metro Phoenix) with amounts generally under
one tenth of an inch so far. With the passage of the front and
the QG forcing, there will be much more to come this morning.
Anticipate the front to reach Sky Harbor by about 4 am. Including
the main batch of follow-on showers behind the more intense band,
much of the precip for metro Phoenix should be over by roughly 9
am. Most of the precip over our higher terrain zones east of
Phoenix will finish a few hours later. However, CAMs indicate
some isolated instability showers in the afternoon (including
metro Phoenix). Including precip since midnight, anticipate
another 0.5 - 1.0 inch for much of metro Phoenix and even 1 - 1.5
in some spots. Anticipate there will be ongoing runoff after the
precip is over - especially over the higher terrain. Thus have
kept the Flash Flood Watch (FFA) going until 5 pm. For southwest
Arizona, the precip should be coming to an end by the time the
Watch expires (5 am) and locations that have already had flooding
will should start to recede. Thus, have not extended the FFA for
that area. For the Winter Storm Warnings, will allow the Joshua
Tree National Park portion to expire at 5 am MST. For our other
area (mainly southern Gila County above 4500ft), snow levels will
continue to fall through the morning and afternoon. Storm total
snow amounts will vary from 1-5 inches between 4500-5500 ft and
5-12 inches above 5500 ft (not a lot of territory above that
elevation within our forecast area).

In the wake of the low pressure system, a ridge will migrate
eastward across the Desert Southwest Saturday and amplify across the
Rockies Sunday. GEFS indicates mid-level heights will remain above
average through early next week, which will translate into above
normal temperatures Monday and Tuesday. There is increasing
likelihood another trough will impact the region during the midweek
period. Both the GEFS and ECMWF-E suggest the potential for
another 0.5-1.0 inch of rain. However, thicknesses point to a warm
system with above normal snow levels.

&&

.AVIATION...Updated at 0627Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:

Strong southerly winds with gusts up to 35 knots are expected
through 10Z as showers gradually increase in coverage and SCT-BKN
ceilings lower to around 4-5 kft. Isolated stronger gusts are
possible ahead of and along the front, particularly with any
convection that is able to mix down higher momentum air aloft
associated with a 50 knot low-level jet. Deeper convection is
generally not expected until the front arrives at the terminals
closer to 10-11Z, along which there should be enough instability
and frontal forcing to produce isolated thunderstorms within a
line of convection. A brief period of IFR-MVFR visibilities and
ceilings are expected with this convective line, with widespread
rain showers behind it through 16-17Z. Southerly wind gusts in
excess of 35 knots will be possible along and ahead of the front,
with westerly wind gusts up to 25 knots expected behind the front.
Ceilings should improve tomorrow with a slight chance of showers
and possibly an elevated thunderstorm or two in the afternoon, but
confidence is too low to include them in the TAF at this time.

Southeast California/Southwest Arizona including KIPL and KBLH:

Light to moderate rain showers will continue through 08-09Z at
KBLH and 12Z at KIPL behind the front with BKN-OVC ceilings
generally staying above 5-6 kft. Further east over eastern Yuma
and La Paz Counties, scattered showers and a few thunderstorms
are expected to develop ahead of a frontal line of convection over
the next few hours before moving into south central Arizona.
Frequent southerly 30-40 knot wind gusts with isolated stronger
gusts are expected ahead of and along the front, particularly with
any convection that is able to mix down higher momentum air aloft
associated with a 50 knot low-level jet. Shower activity will end
from W-NW to E-SE on Friday morning as skies gradually clear with
westerly wind gusts up to 35 knots during the afternoon.

&&

.FIRE WEATHER...
Saturday through Wednesday:
Below normal temperatures Saturday will warm to near normal by
Monday under slow drying conditions and light winds. Moisture
levels should remain fairly elevated through early next week with
minimum RH values mostly above 35 percent. The next low pressure
system then looks to approach from the west late Tuesday into
Wednesday bringing increased moisture, rain chances, and breezy
conditions later Wednesday

&&

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

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flash Flood Watch through this afternoon for AZZ534-537>563.

     Wind Advisory until 4 AM MST early this morning for AZZ534-
     537>544-546-548>551-553>555-559.

     Wind Advisory until 9 AM MST this morning for AZZ545-547-552-
     556>558-560>563.

     Winter Storm Warning until midnight MST tonight for AZZ557-558-
     563.

     Flash Flood Watch until 5 AM MST early this morning for
     AZZ530>533-535-536.

CA...Flash Flood Watch until 4 AM PST early this morning for CAZ569.

     Winter Storm Warning until 4 AM PST early this morning for
     CAZ560.

     Wind Advisory until 3 PM PST this afternoon for CAZ560.

&&

DISCUSSION...AJ/Hirsch
AVIATION...Hopper
FIRE WEATHER...Kuhlman

In the hours before

Local storm report, Nov 29, 1:41 AM MST, 3 hours 19 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
141 AM MST FRI NOV 29 2019

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

1124 PM     FLASH FLOOD      2 SSW VICKSBURG         33.71N 113.77W
11/28/2019                   LA PAZ             AZ   LAW ENFORCEMENT

            ***DELAYED REPORT***...TWO VEHICLES STUCK IN
            WASH ALONG VICKSBURG ROAD WITH WATER UP TO
            THE BOTTOM OF ITS CAR DOOR WINDOWS; RELAYED
            BY LA PAZ COUNTY S.O.

&&

LJH

Local storm report, Nov 29, 1:45 AM MST, 3 hours 15 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
145 AM MST FRI NOV 29 2019

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

1253 AM     FLASH FLOOD      4 NW VICKSBURG          33.78N 113.80W
11/29/2019                   LA PAZ             AZ   LAW ENFORCEMENT

            WASHES RUNNING ALONG STATE ROUTE 72 AND
            BECOMING IMPASSABLE AT MILE POSTS 35, 43,
            AND 45; RELAYED BY LA PAZ COUNTY S.O.

&&

LJH

Local storm report, Nov 29, 1:50 AM MST, 3 hours 10 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
150 AM MST FRI NOV 29 2019

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

1249 AM     NON-TSTM WND GST 1 SSE SKY HARBOR AIRPOR 33.43N 112.01W
11/29/2019  M51 MPH          MARICOPA           AZ   ASOS

            PEAK SOUTHERLY WIND GUST OBSERVED AT SKY
            HARBOR; FREQUENT GUSTS BETWEEN 40-50 MPH
            OVER THE PAST COUPLE HOURS.

&&

LJH

Local storm report, Nov 29, 2:07 AM MST, 2 hours 53 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
207 AM MST FRI NOV 29 2019

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

0142 AM     FLASH FLOOD      4 WSW BLYTHE            33.59N 114.66W
11/29/2019                   RIVERSIDE          CA   DEPT OF HIGHWAYS

            ROADWAY FLOODING REPORTED BY CALIFORNIA
            HIGHWAY PATROL AT STATE ROUTE 78 AND SEELEY
            RD.

&&

LJH

The radar

The Phoenix radar (KIWA), 43 km away, was scanning. The volume nearest the first event began at 12:02 UTC.

Open the radar archive at this moment

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Maricopa

When: November 29, 5:00 AM MST to 11:00 AM MST
Where: Maricopa County, 5.6 mi ESE of Tortilla Flat to 5.34 mi ESE of Tortilla Flat
Cause: Heavy Rain
Reported by: Mesonet
Coordinates: 33.511, -111.285

A powerful Pacific low pressure system moving slowly east across Arizona interacted with deep moisture to produce widespread moderate to heavy rain across higher terrain areas east of Phoenix during the morning hours on November 29th. In addition to influence from frontal lift, isolated thunderstorms helped locally increase rain totals. The heavy rain resulted in some flash flooding that occurred around the Woodbury burn scar area. Based on data from a USGS stream gage, heavy rain on the burn scar caused a rapid rise of nearly 4 feet in Fish Creek Canyon, about 5 miles east of the town of Tortilla Flat. The most significant flash flooding occurred around 0815MST. There were no reports of accidents due to the flash flooding. A Flash Flood Warning was in effect at the time of the flooding.

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 2019 Every state in 2019 This day in weather history Warnings in Arizona, November 2019

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 2026-09-30. Each event’s entry at NCEI: 860227.