Alert archive / Arizona / Flash Flood Warnings in 2018

Flash Flood Warning 31, NWS Phoenix, AZ

July 30, 2018Maricopa County, Arizona

NWS Phoenix, AZ issued this flash flood warning at Jul 30, 2018, 7:24 PM MST for Maricopa County, Arizona. It was in force for 3 hr. 4 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Jul 30, 2018, 7:24 PM MST (02:24 UTC)
Expired: Jul 30, 2018, 10:30 PM MST
In force: 3 hr
Issued by: NWS Phoenix, AZ
Area: Storm-based polygon
Flood severity: None

County Maricopa County, AZ

The radar

The Phoenix radar (KIWA), 60 km from the middle of the area, began a volume at 02:25 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What was reported inside it

Time	Report	Where	Remark
Jul 30, 7:35 PM MST	HEAVY RAIN 0.6	7 N North Scottsdale, AZ	0.60 INCH MEASURED IN 20 MINUTES.
Jul 30, 9:04 PM MST	FLASH FLOOD	7 Sse New River, AZ	SKUNK CREEK WASH FLOWING 5 FOOT DEPTH. NOT OVERFLOWING BANKS AT THIS TIME.
Jul 30, 9:12 PM MST	FLASH FLOOD	7 Sse New River, AZ	FLOODING AT WASH ON MADDOCK ROAD AT 15TH AVE CROSSROADS ROUGHLY 3 FOOT IN DEPTH OVER THE ROAD.
Jul 30, 9:12 PM MST	FLASH FLOOD	7 Sse New River, AZ	FLOODING FROM WASH ROUGHLY 3 FOOT DEPTH OVER MADDOCK ROAD AT 15TH AVENUE CROSSROADS.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

Did it verify

Verified. The Iowa Environmental Mesonet's Cow matched 3 storm reports to this flash flood warning; the first came 100 minutes after it went out.

Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.

The nearest sounding before it

Phoenix, AZ (KPSR), launched 00:00Z, 2.4 hours before the alert went out and 43 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 1123 J/kg
Mixed-layer CIN: -125 J/kg
Mixed-layer LCL: 2603 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: 27 m²/s²
0-3 km storm-relative helicity: 75 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

803 
WGUS55 KPSR 310224
FFWPSR
AZC013-310530-
/O.NEW.KPSR.FF.W.0031.180731T0224Z-180731T0530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Phoenix AZ
724 PM MST MON JUL 30 2018

The National Weather Service in Phoenix has issued a

* Flash Flood Warning for...
  Maricopa County in south central Arizona...

* Until 1030 PM MST.

* At 724 PM MST, Doppler radar indicated thunderstorms producing
  heavy rain across the warned area. Flash flooding is expected to
  begin shortly.

* Some locations that will experience flooding include...
  Phoenix, Scottsdale, Fountain Hills, New River, Cave Creek,
  Carefree, Deer Valley Airport, McDowell Mountain Park, Desert
  Mountain, Scottsdale Airport, Desert Ridge Marketplace, Camp Creek,
  Rio Verde, Anthem and Seven Springs.

* This includes the following highways...
  AZ Interstate 17 between mile markers 217 and 237.
  AZ Route 51 between mile markers 13 and 15.
  AZ Route 101 between mile markers 26 and 40.

LAT...LON 3387 11155 3372 11156 3356 11183 3365 11206
      3378 11223 3401 11213 3398 11184

$$

MS

3 follow-up statements

604 
WGUS75 KPSR 310403
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
903 PM MST MON JUL 30 2018

AZC013-310530-
/O.CON.KPSR.FF.W.0031.000000T0000Z-180731T0530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
903 PM MST MON JUL 30 2018

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1030 PM MST FOR
MARICOPA COUNTY...

At 901 PM MST, Doppler radar indicated thunderstorms have ended 
across the warned area. However, runoff from early storms will 
continue for the next sixty to ninety minutes. Flash flooding is 
expected in the warned area, impacting low water crossings. This 
includes along the Skunk Creek and Cave Creek.

Some locations that will experience flooding include...
Phoenix, Scottsdale, Fountain Hills, New River, Cave Creek, Carefree,
Deer Valley Airport, McDowell Mountain Park, Desert Mountain,
Scottsdale Airport, Desert Ridge Marketplace, Camp Creek, Rio Verde,
Anthem and Seven Springs.

This includes the following highways...
AZ Interstate 17 between mile markers 217 and 237.
AZ Route 51 between mile markers 13 and 15.
AZ Route 101 between mile markers 26 and 40.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

Be especially cautious at night when it is harder to recognize the
dangers of flooding.

&&

LAT...LON 3387 11155 3372 11156 3356 11183 3365 11206
      3378 11223 3401 11213 3398 11184

$$

Iniguez

794 
WGUS75 KPSR 310421
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
921 PM MST MON JUL 30 2018

AZC013-310530-
/O.CON.KPSR.FF.W.0031.000000T0000Z-180731T0530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
921 PM MST MON JUL 30 2018

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1030 PM MST FOR
MARICOPA COUNTY...

At 919 PM MST, flash flooding was reported along the Skunk Creek, 
near the intersection of Desert Hills Drive and 15th Avenue. 
Additional flooding is likely along other washes in the warned area 
as water continues to drain from thunderstorms earlier this evening.

Some locations that will experience flooding include...
Phoenix, Scottsdale, Fountain Hills, New River, Cave Creek, Carefree,
Deer Valley Airport, McDowell Mountain Park, Desert Mountain,
Scottsdale Airport, Desert Ridge Marketplace, Camp Creek, Rio Verde,
Anthem and Seven Springs.

This includes the following highways...
AZ Interstate 17 between mile markers 217 and 237.
AZ Route 51 between mile markers 13 and 15.
AZ Route 101 between mile markers 26 and 40.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

Be especially cautious at night when it is harder to recognize the
dangers of flooding.

&&

LAT...LON 3387 11155 3372 11156 3356 11183 3365 11206
      3378 11223 3401 11213 3398 11184

$$

Iniguez

594 
WGUS75 KPSR 310526
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
1026 PM MST MON JUL 30 2018

AZC013-310535-
/O.EXP.KPSR.FF.W.0031.000000T0000Z-180731T0530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
1026 PM MST MON JUL 30 2018

...THE FLASH FLOOD WARNING FOR MARICOPA COUNTY WILL EXPIRE AT 1030 PM
MST...

The heavy rain has ended and flood waters have receded. Flooding is 
no longer expected to pose a threat.

LAT...LON 3387 11155 3372 11156 3356 11183 3365 11206
      3378 11223 3401 11213 3398 11184

$$

Iniguez

What forecasters said that day

The local office's own words before this flash flood warning went out, 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 this flash flood warning went out at Jul 30, 5:43 PM MST, 1 hour 41 minutes earlier.

Area forecast discussion, Jul 30, 5:43 PM MST, 1 hour 41 minutes before

Area Forecast Discussion
National Weather Service Phoenix AZ
543 PM MST Mon Jul 30 2018

.UPDATE...
Updated Aviation section.

&&

.SYNOPSIS...
The Monsoon High will predominate across the Desert Southwest
through early next week, resulting in temperatures a few degrees
above normal. Storms will be most favored across the higher terrain
east of Phoenix, though there will be a slight chance of
thunderstorms across south-central Arizona each day.

&&

.DISCUSSION...
Today: It looks like clouds were able to clear out early enough
this morning to provide us with sufficient day time heating today.
The upper-level ridge continues to meander near southern Nevada,
providing us with another day of mid-level easterlies. Sufficient
moisture continues to exist across the southern half of the state
with PWs ranging from 1 to 2 inches and the greatest moisture
existing from Maricopa county westward into southeast California.
Currently, scattered storms have already started to develop over
the higher terrain of Gila county, with some isolated stronger
storms apparent on radar. According to the SPC mesoanalysis page,
CAPE values in this region range from 1000 to 2500 J/kg with very
little CIN. In addition, DCAPE values in this same region are
around 1000 to 1300, so stronger storms that develop will have the
potential to produce strong downdrafts. With the steering flowing
being out of the east-northeast, expect activity to continue to
push westward, with most CAMs indicating an outflow boundary
pushing across the western portion of our forecast area, starting
in Gila county around 22Z/23, then pushing through the PHX metro
somewhere between 00Z to 03Z, then exiting Maricopa county
somewhere between 04Z and 05Z. Some of these models also
continue to indicate that the outflow boundary could even push
further westward into La Paz and Yuma county and potentially as
far west as southeast California. So the main question is, will
these outflows be strong enough to generate additional storms over
the lower deserts? The forecast soundings for PHX, show up to
2000 J/kg of CAPE, however there is a pretty moderate cap so it
would take a strong outflow boundary to trigger additional storms
across the lower deserts. Most CAMs remain pretty optimistic today
and do have thunderstorms over the Phoenix metro, so it's not
completely out of the question today and chances definitely look
better than yesterday.

Tuesday-Monday:
Little change in the pattern is anticipated as the aforementioned
Monsoon High persists and meanders across the Desert Southwest.
This will generally result in temperatures a few degrees above
normal and well below records. Latest NAEFS percentiles indicate
low-level mixing ratios near climatology, which will generally
favor the Mogollon Rim and higher terrain for storm activity.
However, it is possible that scattered thunderstorms will
materialize across central Arizona one or two days this week,
despite the PoPs near Climo.

Latest operational GFS and ECMWF depict a well-defined inverted
trough approaching the region late in the weekend or early next
week. This will likely enhance the threat for precipitation along
with other monsoon hazards including strong winds and blowing
dust.

&&

.AVIATION...

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

Strong storms that are ongoing in Gila County and are beginning to
push into far northeastern Maricopa County should at least push an
outflow through KIWA and KSDL around 0130Z and possibly KPHX most
likely after 02Z. These storms would arrive earlier if they
maintained their current intensity and W-SW progress, but some
weakening is still expected based on recent daily trends. It is
worth noting that more hi-res models, including the most recent
HRRR runs and a few of the HREF runs, are pushing at least some of
this convective activity into the lower deserts than yesterday.
The earlier initiation of storms relative to yesterday makes this
more likely as well, so we have added VCTS into KIWA and KSDL from
0130-03Z. We kept VCSH for KPHX since the storms may not be able
to hold together that far west assuming the outflows push ahead of
the storms. However, the strongest thunderstorm cells near Payson
may be able to push into lower deserts and hold together after
sunset due to a shortwave that may be rotating around the ridge
aloft. If this occurs, we will amend as needed. Otherwise, expect
easterly winds to return late overnight with the normal diurnal
progression to westerly by early afternoon tomorrow. Thunderstorm
chances for the lower deserts will be lower tomorrow without the
additional shortwave forcing.

Southeast California/Southwest Arizona including KIPL and KBLH:

Aviation impacts are generally not expected through tomorrow
afternoon aside from some midlevel clouds at KIPL and high clouds
at KBLH. There is a low chances of thunderstorms making it into La
Paz or Yuma Counties that may push a few outflows into the TAF
sites, but chances are too low to include at this time. Apart
from outflows, southeasterly winds at KIPL and southerly winds at
KBLH below 10 knots will be favored.

Aviation Discussion not updated for amended TAFs.

&&

FIRE WEATHER...

Thursday through Monday:

Anticipate a familiar Monsoon weather pattern this week with storm
activity occurring mainly over the higher terrain of Arizona with
only slight chances over the lower deserts. Storm chances depart
from southeast California and southwest AZ on Friday through
Monday as atmospheric moisture content aloft declines somewhat.
Otherwise, minimum humidities will remain above 15% on the lower
deserts (upper teens to mid 20s; mid 20s to mid 30s higher
terrain). Overnight recovery will remain good. Apart from
thunderstorms, winds will be light except for typical afternoon
and evening breeziness.

&&

.SPOTTER INFORMATION STATEMENT...
Skywarn amateur radio Nets may need to be activated for this
afternoon and evening. Spotters should follow standard reporting
procedures.

&&

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

DISCUSSION...Hernandez
AVIATION...AJ
FIRE WEATHER...AJ

In the hours before

Local storm report, Jul 30, 6:51 PM MST, 33 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
651 PM MST MON JUL 30 2018

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

0650 PM     DUST STORM       9 SE QUEEN CREEK        33.13N 111.55W
07/30/2018                   PINAL              AZ   TRAINED SPOTTER

            VISIBILITY LESS THAN 1/2 MILE.

&&

MP

Local storm report, Jul 30, 7:01 PM MST, 23 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
701 PM MST MON JUL 30 2018

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

0635 PM     TSTM WND GST     10 WSW SUNFLOWER        33.84N 111.64W
07/30/2018  E66 MPH          MARICOPA           AZ   PUBLIC

            BARTLETT LAKE.

&&

MP

Local storm report, Jul 30, 7:14 PM MST, 10 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
714 PM MST MON JUL 30 2018

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

0700 PM     DUST STORM       6 NW EAST MESA          33.48N 111.75W
07/30/2018                   MARICOPA           AZ   TRAINED SPOTTER

            REPORT OF 100 YARDS OF VISIBILITY AT VAL
            VISTA AND THOMAS ROAD.

&&

MS

Local storm report, Jul 30, 7:17 PM MST, 7 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
717 PM MST MON JUL 30 2018

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

0645 PM     DUST STORM       6 WSW CAVE CREEK        33.80N 112.07W
07/30/2018                   MARICOPA           AZ   TRAINED SPOTTER

            100 FOOT VISIBILITY IN BLOWING DUST. WIND
            GUSTS TO 40 MPH.

&&

MP

Local storm report, Jul 30, 7:19 PM MST, 5 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
719 PM MST MON JUL 30 2018

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

0705 PM     DUST STORM       6 NNE SANTAN            33.22N 111.75W
07/30/2018                   MARICOPA           AZ   TRAINED SPOTTER

            1/2 MILE VISIBILITY IN BLOWING DUST. WIND
            GUSTS TO 40 MPH.

&&

MP

Local storm report, Jul 30, 7:23 PM MST, 1 minute before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
723 PM MST MON JUL 30 2018

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

0713 PM     TSTM WND GST     2 NE DEER VALLEY        33.69N 112.08W
07/30/2018  E74 MPH          MARICOPA           AZ   ASOS

            74 MPH WIND GUST AT DEER VALLEY ASOS.

&&

MP

The office that day

Everything else NWS Phoenix, AZ issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 30, 5:33 PM MST	Flash Flood Warning	PSR	Gila	3 hr
Jul 30, 5:42 PM MST	Special Weather Statement	PSR		48 min
Jul 30, 6:13 PM MST	Special Weather Statement	PSR		47 min
Jul 30, 6:16 PM MST	Severe Thunderstorm Warning	PSR	Maricopa	29 min
Jul 30, 6:20 PM MST	Dust Storm Advisory	PSR	Maricopa, Pinal	40 min
Jul 30, 6:26 PM MST	Special Weather Statement	PSR		49 min
Jul 30, 6:35 PM MST	Special Weather Statement	PSR	Pinal	40 min
Jul 30, 6:48 PM MST	Special Weather Statement	PSR		42 min
Jul 30, 6:57 PM MST	Dust Storm Warning	PSR	Maricopa, Pinal	48 min
Jul 30, 7:08 PM MST	Dust Storm Advisory	PSR	Maricopa, Pinal	52 min
Jul 30, 7:12 PM MST	Severe Thunderstorm Warning	PSR	Maricopa	33 min
Jul 30, 7:23 PM MST	Severe Thunderstorm Warning	PSR	Maricopa	52 min
Jul 30, 7:30 PM MST	Dust Storm Advisory	PSR	Maricopa, Pinal	60 min
Jul 30, 7:40 PM MST	Flash Flood Warning	PSR	Maricopa, Pinal	3 hr
Jul 30, 7:46 PM MST	Severe Thunderstorm Warning	PSR	Maricopa	44 min
Jul 30, 8:10 PM MST	Dust Storm Warning	PSR	Maricopa, Pinal	65 min
Jul 30, 8:21 PM MST	Special Weather Statement	PSR		39 min
Jul 30, 8:25 PM MST	Dust Storm Warning	PSR	Maricopa, Pinal	65 min
Jul 30, 8:39 PM MST	Areal Flood Advisory	PSR	Maricopa	2 hr
Jul 30, 8:58 PM MST	Flash Flood Warning	PSR	Maricopa	2 hr
Jul 30, 9:15 PM MST	Dust Storm Advisory	PSR	La Paz, Maricopa, Yuma	60 min
Jul 30, 9:33 PM MST	Flash Flood Warning	PSR	Maricopa	117 min
Jul 30, 10:07 PM MST	Dust Storm Advisory	PSR	La Paz, Yuma	38 min

Nearby

Flash Flood Warnings in Arizona, 2018 Every flash flood warning in 2018

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.