Hail and Damaging Winds in Arizona, August 2, 2018

Name: Hail and Damaging Winds in Arizona, August 2, 2018
Start: 2018-08-02T18:45
End: 2018-08-02T22:30
Location: Arizona

August 2, 2018 · NWS PSR · 7 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

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: $117,000
Crop damage: None recorded
Events: 7

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 cluster of very strong thunderstorms moved steadily north and across the west and northwest portions of the greater Phoenix area, including communities of Sun City and Surprise, during the evening hours on August 2nd. The more intense thunderstorms managed to produce unusually heavy amounts of rainfall; there was a confirmed report of 2.9 inches measured in the town of Surprise. Large hail also was reported in the area with diameters in excess of one inch. In addition, some of the storms generated very strong and gusty outflow winds well in excess of 60 mph. The winds downed numerous trees in the vicinity of the Loop 303 and West Bell Road, and also cracked windows in some homes. Despite the intense rainfall, flash flooding was not reported; there were instances of street flooding and an Urban and Small Stream Flood Advisory was issued for the area as a result.

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 2, 12:42 PM MST, 6 hours 3 minutes earlier.

Area forecast discussion, Aug 2, 12:42 PM MST, 6 hours 3 minutes before

Area Forecast Discussion
National Weather Service Phoenix AZ
1242 PM MST Thu Aug 2 2018

.SYNOPSIS...
High pressure will meander across the southwest United States
resulting in slightly above average temperatures, but a gradual
decrease in thunderstorm chances through the weekend, especially
across the lower deserts. More significant moisture will return to
the region by early next week as high pressure builds to the
northwest. Temperatures will consistently remain a few degrees
above normal.

&&

.DISCUSSION...

Visible satellite shows thunderstorm activity gradually increasing
area-wide early this afternoon, and continues to reveal a few
notable features that may support an increase in thunderstorm
potential later this afternoon and evenings. A fast-moving
gravity wave is moving across south-central Arizona, and has
appeared to already enhance convection across south of the Tucson
area. Earlier mid-level cloudiness continues to diminish near the
Phoenix area, while convection becomes more widespread across the
Rim and White Mountains.

The latest hi-res convective allowing guidance continues to
indicate a cluster or two of storms developing across Pima County
into southwest Maricopa and Pinal Counties later this afternoon.
Although steering flow is quite weak, thunderstorms are expected
to propagate and develop towards the Phoenix area later this
afternoon and evening. With weak large-scale forcing for ascent
and new thunderstorm convective development largely dependent on
outflow boundaries, coverage is still uncertain. Can't rule out a
few strong wind gusts, locally heavy rain, and patchy blowing
dust with any thunderstorms/outflows that develop. Farther west,
thunderstorms developing over the higher terrain of northern Baja
County are approaching western Imperial County in association with
a remnant MCV. Additional convection has been noted across JTNP.
Blowing dust and locally strong wind gusts will accompany any
storms that develop.

The upper ridge across the western CONUS will
remain dampened through the weekend by a belt of moderate
westerlies across the Great Basin, which will keep our
temperatures slightly above normal. Within this regime, drier air
aloft will also overspread the region this weekend and result in a
downtick in thunderstorm activity area-wide. However, there will
still be enough moisture around to support a few thunderstorms
over southern Gila County.

By next week, a seasonably strong upper trough will develop off
the Pacific Northwest coast, and correspond with a significant
amplification of the upper ridge over the western CONUS. The
parent anticyclone will shift northwestward towards the Great
Basin while simultaneously strengthening. While this may result in
a gradual warming trend for southeast California, it should be far
enough removed to keep excessive heat concerns at bay for the time
being. During this time period, moisture will return back closer
to seasonal normals for August, and bring back daily chances for
thunderstorms. This should set up a Type II monsoonal pattern and
place south-central Arizona within east-northeast flow aloft.
Temperatures should also remain fairly consistent during this
period.

&&

.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:
Based on observational data and preponderance of latest high
resolution model output, it looks far more likely that sct
thunderstorms will impact the Phoenix metro, and particularly KPHX.
The pattern conceptually matches storms forming over SW Maricopa Co
generating outflow and blowing dust moving north towards the
terminals. Potentially aided by lift from the Estrellas, storms
could directly impact KPHX and have added a Tempo group around 02Z.

The most likely time frame of IFR conditions due to TSRA and BLDU
looks to be 02Z-05Z with showers lingering for a few more hours
afterwards. Gusty SSW winds with the outflow would become extremely
variable in direction with the passage of any storms, and wake low
development could cause a period of gusty north winds washing back
into terminal locations. Not convinced coverage will be that
extensive throughout the metro and only included VCTS for KIWA and
KSDL sites, though BLDU could become a problem at these location as
well.

Southeast California/Southwest Arizona including KIPL and KBLH:
Thunderstorm chances and associated impacts are the primary aviation
concerns this afternoon and evening. Storms were already developing
along the Baja spine this morning, and steering flow could drive
TSRA into KIPL this afternoon. Chances of directly impacting the
terminal location is too small to include in this TAF package, with
only a wind shift currently noted. Storm chances at KBLH are much
less, and the typical south winds should prevail.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Sunday through Thursday:
Thunderstorm chances will be more relegated to higher terrain
areas of Gila County on Sunday as the overall atmospheric moisture
content declines. As high pressure redevelops to the northwest,
moisture will return to the area and bring an increase in
thunderstorm chances to the lower deserts. Otherwise, minimum
humidities will remain in a 15-30% range following fair to good
overnight recovery. Apart from thunderstorms, winds will be light
except for typical afternoon and evening upslope breeziness.
Little temperature trend expected during the five day period, with
high temperatures remaining a few degrees or so above seasonal
normals each day.

&&

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

&&

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

DISCUSSION...Rogers
AVIATION...MO
FIRE WEATHER...Rogers/CB

In the hours before

Local storm report, Aug 2, 6:38 PM MST, 7 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
638 PM MST THU AUG 2 2018

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

0624 PM     DUST STORM       4 E AHWATUKEE FOOTHILLS 33.31N 111.99W
08/02/2018                   MARICOPA           AZ   TRAINED SPOTTER

            SPOTTER REPORTS VISIBILITY OF LESS THAN 1/4
            MILE AND DROPPING.

&&

TD

Local storm report, Aug 2, 6:39 PM MST, 6 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
639 PM MST THU AUG 2 2018

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

0635 PM     DUST STORM       3 WNW GILBERT           33.36N 111.84W
08/02/2018                   MARICOPA           AZ   TRAINED SPOTTER

            TRAINED SPOTTER REPORTS 1/4 MILE VISIBILITY
            IN BLOWING DUST.

&&

MP

Local storm report, Aug 2, 6:40 PM MST, 5 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
640 PM MST THU AUG 2 2018

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

0626 PM     DUST STORM       2 E CHANDLER            33.29N 111.82W
08/02/2018                   MARICOPA           AZ   TRAINED SPOTTER

            SPOTTER REPORTS VISIBILITY LESS THAN 1/4
            MILE DUE TO DUST AND WINDS OF ABOUT 20MPH.

&&

TD

Local storm report, Aug 2, 6:41 PM MST, 4 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
641 PM MST THU AUG 2 2018

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

0627 PM     DUST STORM       PHOENIX MESA GATEWAY    33.31N 111.66W
08/02/2018                   MARICOPA           AZ   AWOS

            MESA GATEWAY AWOS REPORTS 1/8 MILE
            VISIBILITY IN BLOWING DUST.

&&

MP

Local storm report, Aug 2, 6:42 PM MST, 3 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
642 PM MST THU AUG 2 2018

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

0629 PM     DUST STORM       3 NNW CHANDLER          33.33N 111.89W
08/02/2018                   MARICOPA           AZ   TRAINED SPOTTER

            SPOTTER REPORTS NEAR ZERO VISIBILITY DUE TO
            DUST.

&&

TD

Local storm report, Aug 2, 6:44 PM MST, 1 minute before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
644 PM MST THU AUG 2 2018

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

0630 PM     DUST STORM       5 ENE SUN LAKES         33.25N 111.79W
08/02/2018                   MARICOPA           AZ   PUBLIC

            SPOTTER REPORTS VISIBILITY OF LESS THAN 1
            MILE DUE TO DUST.

&&

TD

The radar

The Phoenix radar (KIWA), 77 km away, was scanning. The volume nearest the first event began at 01:47 UTC.

Open the radar archive at this moment

Event by event

4 thunderstorm wind, 2 hail, 1 heavy rain. Local standard time, as filed.

Thunderstorm Wind, Maricopa

When: August 2, 6:45 PM MST to 7:30 PM MST
Where: Maricopa County, 2.07 mi S of Beardsley
Measured: 61 kt (70 mph) estimated gust
Property damage: $30,000
Reported by: Trained Spotter
Coordinates: 33.640, -112.380

A large cluster of thunderstorms moved steadily north and across the western portion of the greater Phoenix area during the evening hours on August 2nd. Some of the stronger storms generated gusty damaging outflow winds that affected communities such as Sun City West and Waddell. According to a trained weather spotter located about 2 miles southwest of Sun City West, at 1845MST gusty winds estimated to be as high as 70 mph downed about 20 trees with diameters of 3 to 4 inches. Several larger trees with 8 inch diameter trunks were also downed. The downed trees were located along Bell Road between Litchfield and Reems Roads. Between 1845MST and 1930MST, multiple reports of downed trees were received from the public as well as trained spotters; most of the reports were near Bell Road between the Loop 303 and Litchfield road.

Thunderstorm Wind, Maricopa

When: August 2, 6:45 PM MST
Where: Maricopa County, 1.8 mi NW of Waddell
Measured: 61 kt (70 mph) estimated gust
Property damage: $75,000
Reported by: Public
Coordinates: 33.640, -112.450

A large cluster of very strong thunderstorms moved steadily to the north across the western portion of the greater Phoenix area during the evening hours on August 2nd. Some of the storms affected homes from the town of Surprise westward past the Loop 303 highway. The more intense thunderstorms generated damaging outflow winds; according to a public report gusty microburst winds estimated to be at least 70 mph in strength generated minor to moderate roof damage to many houses in a subdivision located north of Bell Road and west of the Loop 303. The homes were located just to the southeast of Arizona Traditions Golf Club.

Thunderstorm Wind, Maricopa

When: August 2, 6:48 PM MST to 6:50 PM MST
Where: Maricopa County, 1.86 mi ENE of Waddell
Measured: 56 kt (64 mph) estimated gust
Property damage: $4,000
Reported by: Public
Coordinates: 33.630, -112.400

A cluster of very strong thunderstorms moved steadily north and across the western portion of the greater Phoenix area during the evening hours on August 2nd. Some of the more intense storms produced gusty and damaging outflow winds that affected communities such as Waddell and Surprise. According to a report from the public, about 2 miles northwest of Waddell and just west of Surprise, strong outflow winds downed several trees and cracked the window in one of the homes in the area. Wind gusts were estimated to be as high as 65 mph. No injuries were reported.

Hail, Maricopa

When: August 2, 6:55 PM MST
Where: Maricopa County, 1.8 mi NW of Waddell
Measured: 1 in hail
Reported by: Public
Coordinates: 33.640, -112.450

A cluster of strong thunderstorms moved north across the western portion of the greater Phoenix area during the evening hours on August 2nd. A few of the more intense storms generated large hail and affected areas west of the Loop 303 highway and along Bell Road. According to a trained spotter, large hail was measured about 4 miles northwest of Waddell, to the west of the Loop 303 highway and along Bell Road. The hailstones had a diameter of around one inch. No damaged was reported due to the large hail.

Hail, Maricopa

When: August 2, 7:20 PM MST
Where: Maricopa County, 1.38 mi N of Waddell
Measured: 0.88 in hail
Property damage: $2,000
Reported by: Public
Coordinates: 33.640, -112.430

A cluster of strong thunderstorms moved steadily north across the western portion of the greater Phoenix area during the evening hours on August 2nd. Some of the stronger storms generated large hail in addition to intense rainfall. According to a report received from the public, large hail fell about 3 miles northwest of Waddell, near the intersection of Cotton Road and Bell Road, just west of the Loop 303 highway. At least one of the hailstones had a diameter measured to be 0.88 inches. At the same time of the hail, a downburst occurred that blew down 2 trees.

Heavy Rain, Maricopa

When: August 2, 7:45 PM MST to 10:30 PM MST
Where: Maricopa County, 1.8 mi NE of Waddell
Property damage: $5,000
Reported by: Trained Spotter
Coordinates: 33.640, -112.410

A cluster of very strong thunderstorms moved steadily north across the western portion of the greater Phoenix area during the evening hours on August 2nd. Some of the stronger storms produced intense rainfall with peak rain rates well in excess of one inch per hour. The heavy rains led to local street flooding west of Surprise and near Sun City West, especially along Bell Road. According to a trained weather spotter, at 1915MST very heavy rain was measured along Bell Road just to the east of the Loop 303 highway. 2.05 inches of rain was measured in the area. Downbursts accompanied the heavy rain which caused trees in the area to be downed. Heavy rain led to street flooding and the Surprise Police Department closed Sunrise Boulevard at Bell Road due to water across the road. An Urban and Small Stream Flood Advisory was issued for the area at 1934MST and it remained in effect until 2230MST. There were other heavy rain reports in the area, based on CocoRAHS weather station observations. One such station to the southeast of the Loop 303 and Bell Road intersection measured 1.18 inches of rain. The most significant report came from another CocoRAHS station in Surprise that measured a storm total rainfall of 2.90 inches. The station ID was AZ-MR-42. There were no flash flooding reports in Surprise, despite the very heavy rainfall that occurred.

Thunderstorm Wind, Maricopa

When: August 2, 7:53 PM MST to 7:55 PM MST
Where: Maricopa County, 4.42 mi SW of Wittmann
Measured: 52 kt (60 mph) estimated gust
Property damage: $500
Reported by: Trained Spotter
Coordinates: 33.740, -112.590

A large cluster of intense thunderstorms moved north through the western portion of the greater Phoenix area during the evening hours on August 2nd. Some of the stronger storms produced gusty and damaging outflow winds and affected areas around the community of Wittmann. A trained weather spotter reported that a wind gust, estimated to be about 60 mph in strength, snapped a branch off of one of his trees. The branch had a diameter of 5 inches.

What these are

Thunderstorm Wind: Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.
Hail: Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
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 2018 Every state in 2018 This day in weather history Warnings in Arizona, August 2018

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: 762997, 763051, 763019, 763022, 763023, 763027, 763021.