Flooding in Arizona, February 22 to 26, 2020

Name: Flooding in Arizona, February 22 to 26, 2020
Start: 2020-02-22T12:00
End: 2020-02-26T09:15
Location: Arizona

February 22 to 26, 2020 · NWS PSR · 3 events in 2 counties and zones

Where it happened

Every event with a place to put it. Tap one for its entry below.

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Wind
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Heat and drought
Cold
Fire, smoke and dust
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The toll

Deaths: 0
Injuries: 0
Property damage: $31,000
Crop damage: None recorded
Events: 3

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 strong, wet Pacific upper level low pressure system spread copious amounts of moisture into south central Arizona on Saturday February 22nd; as a result widespread rain developed early in the morning and the moderate to heavy rain persisted for much of the day. The heaviest rainfall amounts occurred over higher terrain areas to the east of Phoenix; most of the rain gages in the area measured between 1.25 and 3 inches with the most significant rain occurring during the morning hours. The excessive rain resulted in a few episodes of areal flooding which included the Sycamore Creek and Tonto Creek basins. During the afternoon hours, local law enforcement reported multiple roads closed due to flooding in the Tonto Creek basin; the closures occurred to the northwest of Lake Roosevelt. An areal flood warning was issued for the basin due to elevated flow in the creek and the warning persisted for several days. In addition, during the evening hours a family of 5 drove into Sycamore Creek, which was flowing heavily, and became stranded necessitating a water rescue.

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 Feb 22, 11:13 AM MST, 47 minutes earlier.

Area forecast discussion, Feb 22, 11:13 AM MST, 47 minutes before

Area Forecast Discussion
National Weather Service Phoenix AZ
1113 AM MST Sat Feb 22 2020

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
A wet Pacific weather system will likely bring light to moderate
rainfall across much of the region today with lingering chances
of showers and possibly a few thunderstorms through early Sunday
morning. Temperatures this weekend will fall back to near or below
normal readings before recovering slightly into early next week.
Dry conditions are expected next Monday into the middle of next
week under generally clear skies along with a steady warming
trend.

&&

.DISCUSSION...
Current water vapor imagery shows a deep plume of subtropical
moisture flowing into the Southwest ahead of a low pressure system
that is currently positioned off the California coast. Objective
analysis shows a tongue of anomalously high precipitable water
values of 1.00 to 1.40 pushing northward into southern Arizona
leading to a coagulation of showers near the Arizona/Mexico border.
The Phoenix radar has been fairly quiet with mostly weak isolated
showers so far.

Shower activity will spread throughout central Arizona, and possibly
as far west as southeast California, as the moisture surges deeper
into the region. Recent forecast trends for storm total QPF have
varied somewhat but deep moisture should lead to higher rainfall
potential. The Phoenix area could see 0.50-1.00" while higher
amounts of 1.25-2.00" may fall over the higher terrain north and
east of the Valley. A Flash Flood Watch is in effect from 5 AM
through 11 PM today for much of central Arizona where showers and/or
thunderstorm are more likely to produce excessive rainfall. Of
particular concern, Tonto Creek is forecast to rise above action
stage as runoff from nearby mountains flows into the basin.

Most shower activity this morning will be light to moderate. By late
morning, some areas may see clearing skies and a few degrees of
afternoon warming. During this time, the low will move over Southern
California improving atmospheric conditions for convection such as
favorable jet streak positioning and dynamics, increasing shear and
higher instability. The latest HREF and several current runs of hi-
resolution models support a broad area 200-500 j/kg of MUCAPE across
central Arizona with the potential for pockets of higher instability
where any clearing is realized. Those conditions combined with
frontal forcing will lend to propitious convective potential. While
coverage of storms is more likely to be isolated than widespread,
any thunderstorms that form may produce heavy rain, hail, and strong
winds. Storms reaching severe criteria cannot be ruled out.

Rain chances are much lower for areas along and west of the Colorado
River. However, a tightening pressure gradient as the low moves over
California will induce strong winds with gusts of 25-40 mph through
Imperial County and eastward into southwestern Arizona.

By Sunday, the aforementioned system will eject to our east allowing
the area dry. Isolated areas of patchy fog may form early Sunday
morning in areas that receive adequate precipitation to saturate air
near the surface and overnight clearing to enhance radiational
cooling. The likeliest places to see fog will be in Pinal County and
southern portions of metro Phoenix. Otherwise, global ensembles show
ridging forming over the western US next week allowing temperatures
to gradually warm each day.

&&

.AVIATION...Updated at 1813Z.

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

Current widespread rainfall across the Phoenix area is expected to
continue until frontal passage (about 23-00Z) with southerly
crosswinds likely for a time ahead of the front. CIGS are also
expected to remain in the 2-5k foot range during this period...with
visibilities as low as 2SM in heavier showers. Once the front
passes, expecting wind shift to sw-ly with CIGS rising into the 5-7k
foot range, and showers becoming more scattered, with noticeable
breaks between the showers. Current though is that best chance for
TS to remain north and east of Phoenix, so confidence is still not
high enough to mention VCTS in the TAFS. Lingering showers will
still be possible through the evening before fully diminishing
Sunday morning. Winds are likely to remain from a sw-ly direction
through the night, with lingering SCT-BKN CIGS in the 4-6k foot
range. Chances for morning fog look low at this time due to this
lingering cloudiness. CIGS to fall into the FEW-SCT range by Sun
afternoon.

Southeast California/Southwest Arizona including KIPL and KBLH:

Showers have generally moved east of the Colorado River, with
additional showers unlikely through the rest of the TAF period, but
still cannot fully rule out isolated convection in the afternoon.
Winds will be the bigger impact during the period, with speeds up to
15-20 kts and gusts to 25-30 kts out of the west at KIPL and more
out of the south-southwest at KBLH during the afternoon. Surface
winds should gradually subside during the overnight hours at both
locations. FEW-SCT mid and high clouds should prevail through most
of the period.

&&

Monday through Friday:
No significant changes to the extended outlook...Conditions will
continue to dry with minimum RH values dropping into the 10-25%
range by midweek and declining overnight recoveries. Winds will
behave more typical for the week with directions favoring
terrain/diurnal trends. Speeds will also remain fairly light
outside of occasional afternoon breezes.

&&

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

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flash Flood Watch through this evening for AZZ534-537-538-
     540>553-555>558-560>563.

CA...Wind Advisory from 10 AM this morning to 10 PM PST this evening
     for CAZ562.

&&

DISCUSSION...Deems
AVIATION...Percha/Benedict
FIRE WEATHER...Deems

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

3 flood. Local standard time, as filed.

Flood, Gila

When: February 22, 12:00 PM MST to 7:00 PM MST
Where: Gila County, 3.27 mi SSE of Globe to 1.31 mi SE of Little Acres
Cause: Heavy Rain
Property damage: $1,000
Reported by: Law Enforcement
Coordinates: 33.354, -110.765

A strong Pacific low pressure system spread copious amounts of moisture into south central Arizona during the day on Saturday February 22nd; this led to widespread moderate to heavy rain which began in the morning hours. Although rain rates were never overly high, the steady rain allowed for some locations to pick up upwards of 3 inches during the day and some areal flooding occurred as a result. Flooding occurred in the area around Globe; as reported by the Gila County Sheriff's Office at 1536MST flooding caused the Beer Tree Crossing at Pinal Creek to become closed. The closure was about 1 mile to the southeast of Globe. While there were no flood warnings issued, an areal flood advisory was put into effect shortly after the report of the closure at the Beer Tree Crossing.

Flood, Gila

When: February 22, 1:00 PM MST to February 26, 9:15 AM MST
Where: Gila County, 7.91 mi NNW of Government Hill to 4.83 mi SSE of Punkin Center
Cause: Heavy Rain
Property damage: $5,000
Reported by: Law Enforcement
Coordinates: 33.773, -111.211

A strong upper level low pressure system spread copious amounts of moisture into south-central Arizona on Saturday February 22nd; this lead to widespread moderate to heavy rain across the high terrain to the northeast of Phoenix. Significant amounts of rain fell in the Tonto Creek basin with gage reports in the area measuring as high as 3 inches during the event. This led to areal flooding in the basin which resulted in several low water crossings becoming inundated. At 1303MST local law enforcement reported a cross road at Tonto Creek closed due to flooding. Later in the afternoon, at about 1713MST, law enforcement reported that the Bar X crossing at Tonto Creek was closed due to the flooding. Both closures were reported by GCSO. In addition, the AHAPS stream gage called Tonto Creek at Roosevelt measured flow significantly above action stage on Saturday, and the elevated flow continued into the middle of the following week. An Areal Flood Warning was issued due to the elevated streamflow. Flow above action stage results in flooding of several low water crossings in the creek.

Flood, Maricopa

When: February 22, 3:45 PM MST to 11:00 PM MST
Where: Maricopa County, 8.37 mi E of Ft McDowell to 10.22 mi E of Ft McDowell
Cause: Heavy Rain
Property damage: $25,000
Reported by: Broadcast Media
Coordinates: 33.650, -111.537

A strong Pacific upper low spread copious amounts of moisture into south-central Arizona on Saturday February 22nd; this led to widespread moderate to heavy rain across higher terrain areas to the northeast of Phoenix. The excessive rain resulted in some areal flooding during the afternoon and evening hours, affecting the Sycamore Creek basin. According to local broadcast media, at roughly 2115MST a family of 5 drove their vehicle into Sycamore Creek, about 7 miles to the north-northwest of Saguaro Lake. Due to flowing water in the creek, their vehicle became stuck and necessitated a water rescue. There were several other vehicles trapped on river banks awaiting the waters to recede so that they could proceed. There were no reports of accidents, injuries or fatalities. At the time there were no flood warnings in effect for the area as heavy rain had ended a long time ago.

What these are

Flood: Flooding that develops more slowly than a flash flood: rivers leaving their banks, or water standing over land for an extended time.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Arizona in 2020 Every state in 2020 This day in weather history Warnings in Arizona, February 2020

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: 870338, 870334, 870340.