Arizona, 2017Heavy Rain in Arizona, July 22, 2017
July 22, 2017 · NWS PSR · 1 event in 1 county or zone
Scattered monsoon thunderstorms developed to the east of Phoenix during the afternoon hours on July 22nd and some of the stronger storms were focused across the far east portions of the greater Phoenix area including some higher terrain locations such as Superior. Locally heavy rainfall was observed; a trained spotter near the town of Superior measured almost three quarters of an inch within a…
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- Deaths
- 0
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- 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.
Scattered monsoon thunderstorms developed to the east of Phoenix during the afternoon hours on July 22nd and some of the stronger storms were focused across the far east portions of the greater Phoenix area including some higher terrain locations such as Superior. Locally heavy rainfall was observed; a trained spotter near the town of Superior measured almost three quarters of an inch within a 20 minute period. The rain led to small stream flooding and necessitated the issuance of a Flood Advisory across communities such as Sunflower, Roosevelt, Four Peaks and Punkin Center. Flash Flooding was not observed however.
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 Jul 22, 1:27 PM MST, 33 minutes earlier.
Area forecast discussion, Jul 22, 1:27 PM MST, 33 minutes before
Area Forecast Discussion
National Weather Service Phoenix AZ
127 PM MST Sat Jul 22 2017
.SYNOPSIS...
Thunderstorm activity...most numerous over the higher
terrain...will continue through the weekend with chances expanding
into southeast California Monday. Additional cloud cover and a
moist atmosphere will lead to seasonally cool temperatures through
early next week. Drier southwesterly flow aloft develops next
week. This will lead to drier air and warmer temperatures along
with fewer storms region-wide.
&&
.DISCUSSION...
Today through Monday:
Analysis of the 500 millibar level shows the center of the anti-
cyclonic rotation situated over Utah. The GOES-16 experimental
moisture channel shows some upper level subsidence with drier air
aloft in association with the anti-cyclone, although some upper
level moisture is trying to filter in. There is ample low level
moisture as this morning's surface analysis indicated dew points
above 60 degrees across the lower desert, while the 12Z sounding
revealed thick moisture up to 500mb, and nearly 1.9 inches of
precipitable water.
Satellite imagery also reveals an inverted trough lurking over
Sonora, Mexico with ongoing convection that has allowed storms to
form over southeast Arizona this morning. For central Arizona,
storms are initiating over the White Mountains and the Rim in
response to another wave discernible in the 500mb wind field. The
steering flow will be from north to south again which may be
favorable for storms, and associated outflows, to make way into
the lower desert. The Storm-Scale Ensemble of Opportunity (SSEO)
highlights all of Gila County and a portion of northeastern
Maricopa and Pinal counties as having the greatest chance for
storms. Given the ample low level moisture, thunderstorms will be
capable of producing heavy rains. Therefore, flooding will
continue to be the primary concern.
Thunderstorm chances will continue into Sunday and Monday,
especially as the aforementioned lurking inverted trough
continues to its westward journey. As the trough approaches,
favorable atmospheric dynamics for storms should spread over the
southern half of Arizona and into southeast California. All places
look to have some chance for rain, including Yuma and El Centro,
which have largely been left out of the monsoon activity so far.
Again, flooding looks to be the primary concern; however,
southeasterly steering winds both Sunday and Monday could lead to
blowing dust issues for I-10 corridor between Phoenix and Tucson.
Tuesday through Saturday:
We start to see a break in monsoon activity as dry southwesterly
flow starts to develop and pushes moisture north and east. This
will keep thunderstorm chances confined to the higher terrain
north and east of Phoenix each afternoon. With the steering flow
out of the southwest, it's going to be extremely difficult for
outflows and/or thunderstorms that develop over the higher
terrain to propagate into the lower deserts.
Although still too far out for much confidence, it's looking like
the 500 mb high starts to center itself around the four corners.
This would provide us with that moist easterly flow we need to
get an increase in monsoonal moisture and increased chances for
thunderstorms across the lower deserts again.
&&
.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:
Isolated light showers/virga will brush northern and eastern
portions of metro Phoenix through 15Z before dissipating.
Probability of passing directly over the TAF sites too low to
insert TEMPO in the TAFs for those showers. Otherwise, variable
mid clouds this morning. More clouds and scattered light showers
over the higher terrain north and east of metro Phoenix this
morning. Later today, look for thunderstorm development once again
over the favored higher terrain locations. With northeasterly
steering flow, expect northern and eastern portions of metro
Phoenix to be affected by storms. However, confidence too low on
timing and locations of storms to reflect in TAFs but expect to at
least see some outflows after 00Z. Otherwise surface winds will
follow familiar diurnal patterns.
Southeast California/Southwest Arizona including KIPL and KBLH:
Skies will be mostly clear today and tonight. An exception will be
La Paz County where isolated thunderstorm development is possible
this afternoon and evening. Surface winds will follow familiar warm
season patterns favoring south and southeast directions.
Aviation discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Monday through Friday:
Shower and thunderstorm potential expands westward into southeast
California Monday with minimum humidities well above 20% across
the forecast area. A drying trend begins Tuesday with declining
humidities and an eastward retreat of storm chances. Overnight
humidity recovery remains fair to good. Apart from thunderstorms,
winds will follow familiar warm season patterns.
&&
.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...Deemer/Hernandez
AVIATION...AJ
FIRE WEATHER...AJ
Heavy Rain, Pinal
- When
- July 22, 2:00 PM MST to 5:45 PM MST
- Where
- Pinal County, 1.38 mi N of Superior
- Reported by
- Trained Spotter
- Coordinates
- 33.300, -111.100
Scattered thunderstorms developed across the far eastern portion of the greater Phoenix area, including higher terrain locations of far northeast Maricopa County, during the afternoon hours on July 22nd. Locally heavy rain was observed in some locales, including the community of Superior. At 1615MST a trained spotter 1 mile northeast of Superior measured 0.74 inches of rain within a 20 minute period. Locally heavy rain such as this necessitated the issuance of a Small Stream Flood Advisory for areas near to and to the north of Superior. The advisory was issued at 1552MST and ran through 1745MST.
- 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.
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