Flash Flood Warning 21, NWS Phoenix, AZ

688 
WGUS75 KPSR 180437
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
937 PM MST Sun Jul 17 2022

AZC013-180545-
/O.CON.KPSR.FF.W.0021.000000T0000Z-220718T0545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
937 PM MST Sun Jul 17 2022

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1045 PM MST THIS 
EVENING FOR MARICOPA COUNTY...

At 937 PM MST, Doppler radar indicated thunderstorms have ended 
across the warned area. However, between 1 and 1.5 inches of rain 
have fallen. Flash flooding is ongoing or expected to begin shortly.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Radar.

IMPACT...Flash flooding of small creeks and streams, urban areas,
         highways, streets and underpasses as well as other poor
         drainage and low-lying areas.

Some locations that will experience flash flooding include...
  Mesa, Chandler, Gilbert, Freestone Park, Gilbert City Hall, 
  Downtown Mesa, Superstition Springs Mall and Fiesta Mall.

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 3343 11181 3343 11174 3340 11169 3334 11168
      3332 11173 3332 11181 3337 11187 3341 11185

FLASH FLOOD...RADAR INDICATED

$$

18

717 
WGUS75 KPSR 180541
FFSPSR

Flash Flood Statement
National Weather Service Phoenix AZ
1041 PM MST Sun Jul 17 2022

AZC013-180551-
/O.EXP.KPSR.FF.W.0021.000000T0000Z-220718T0545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maricopa AZ-
1041 PM MST Sun Jul 17 2022

...FLASH FLOOD WARNING WILL EXPIRE AT 1045 PM MST THIS EVENING FOR 
MARICOPA COUNTY...

Flood waters have receded. The heavy rain has ended. Flooding is no 
longer expected to pose a threat. Please continue to heed remaining 
road closures.

LAT...LON 3343 11181 3343 11174 3340 11169 3334 11168
      3332 11173 3332 11181 3337 11187 3341 11185

$$

18

Area Forecast Discussion
National Weather Service Phoenix AZ
454 PM MST Sun Jul 17 2022

.UPDATE...
Updated Aviation section.

&&

.SYNOPSIS...
The Excessive Heat Warning for the Imperial Valley and Salton Sea
areas remains in effect today. A slight dip in temps expected
Monday across the foreast area, but overall temperatures will
remain hot with very little change in highs expected for the rest
of the work week. Sufficient monsoonal moisture will be in place
for at least the next week, providing daily opportunities for
shower and thunderstorm activity, especially over the high terrain
in north/east/southeast Arizona but at times across the lower
deserts as well.

&&

.DISCUSSION...
A broad ridge of high pressure remains centered near the 4-corners
region this afternoon with 500 hPa heights near 594 dm over
south-central AZ. Anomalously strong easterly flow continues aloft
with 500 hPa wind speeds of 20-25 kts. Compared to yesterday, PWAT
remains similar at near 1.3-1.6" (highest towards Yuma), but with
some changes noted, including drier air in the mid levels but
more moisture in the boundary layer. Skies are mostly clear at the
moment due to subsidence behind the wave that moved through last
night, but with some convection beginning to form along the Rim.

In the short term, today is expected to mostly be a quiet day,
with the PV anomaly that kicked off yesterday's weather now well
to the southwest of the area. High temperatures will drop slightly
from yesterday and peak around 111F for Phoenix, but this is
still near 5 degrees above normal. In southeast California it will
be just a touch warmer with highs of 111-114F. A few storms along
the higher terrain north and east of Phoenix are certainly
possible.

By this evening model guidance suggests that another weak wave
will begin to impact the area. Anomalous mid level easterly flow
will continue, but some upper level support will also develop with
300 hPa winds of 30-40 kts and a somewhat favorable diffluent
zone aloft. Additionally, PWAT will increase this evening as the
typical Gulf Surge and possibly some diffuse outflow activity
brings additional moisture north. HREF guidance shows a
preferential zone of activity developing in southwest Arizona,
focusing on western Maricopa County through La Paz County.
Probabilities of 30 kt winds or greater surface winds approach
50% in the late evening and overnight hours, with a very marginal
risk of severe level wind possible. The main impacts look to be
lightning, wind, and dust, but localized heavy rain leading to
flooding is also possible. In the Phoenix area conditions look
less favorable, but a few HREF members have shown some activity
over the area and so an isolated thunderstorm is possible (15%
chance.)

Any storm activity should wrap up by mid morning on Monday. For
much of the rest of the week, conditions will probably be mostly
quiet as the center of the high pressure moves either directly
over the forecast area, or close to it. Not only will this help to
squash convection through subsidence, but shear will be much
lower, and there will be less of a tendency for deep moisture
transport into the area. Even though the risk of valley storms
will be low, afternoon storms over the higher terrain should
continue. If the high pressure sets up a little to the west of the
area, it is possible that storm chances in the valleys near
Phoenix could be a bit higher.

In terms of heat, high temperatures will mostly settle near
107-111F for the valleys for the next week. The NBM is showing a
25% chance or better of reaching 110F each day. There is a bit of
a signal for a return to wetter monsoon conditions near the end of
the forecast period as the upper level high moves east again.
Cluster analysis confirms that the model solutions where the
ridge is further east and stronger (with lower heights towards
southern California) offer better moisture return. Most ensemble
systems are showing a decent increase in PWAT and rain chances so
this will be something to keep an eye on going forwards.

&&

.AVIATION...Updated at 2354Z.

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

Midtropospheric high pressure is centered over northwest New
Mexico this afternoon generating southeasterly steering flow for
thunderstorms. Thus, the storms on the Rim have been reluctant to
move toward the Valley floor. However, outflow from those storms
(and any others for that matter) can generate new storms closer to
the metro area which in turn could lead to outflow causing a wind
shift at the TAF sites. So far, the outflow from the Rim storms
appears to be weakening though some new development has been
generated south of the Rim over eastern Gila County. In addition
to the Rim storms, there is also activity over Pima and eastern
Pinal County. At this time, the TAF sites most likely to see a
shift away from the current westerly surface winds are KIWA and
KSDL. But, the preexisting westerly winds will make it hard for
outflow from the northeast and/or southeast to overspread the
Valley floor this evening. Thus, the 00Z TAF package does not have
a direction change at KPHX or KDVT. In fact, in the absence of any
outflows, westerly winds will remain gusty long past sunset and
possibly past midnight. In the overnight hours, isolated to
scattered showers with embedded thunderstorms, are anticipated to
pass through western Maricopa County (and Yuma and La Paz
Counties) as a disturbance moves through before clearing from
southeast to northwest after 12Z. Those showers could brush the
metro area but confidence too low to reflect in the TAFs.
Otherwise, anticipate a batch of increasing mainly high clouds.
During the day Monday, anticipate westerly winds to prevail (with
afternoon gustiness) but with even lower likelihood of storms
affecting the metro area.

Southeast California/Southwest Arizona including KIPL and KBLH:

South and southeasterly surface winds will prevail through Monday.
During the overnight hours, anticipate isolated to scattered
showers, with embedded thunderstorms, to pass through La Paz and
Yuma Counties and possibly over the Lower Colorado River Valley.
Confidence in SHRA/TSRA occurring at KBLH is too low to reflect in
the TAF at this time. But, that activity could create variable
wind directions. Otherwise, anticipate an increase in mainly high
clouds tonight followed by decreasing clouds from southeast to
northwest during the day Monday.

&&

.FIRE WEATHER...
Sufficient monsoonal moisture will remain in place, resulting in
daily opportunities for shower and thunderstorm activity (best
chances across the high terrain in north/east/southeast Arizona).
MinRH values will remain mostly above 15% with overnight
recoveries between 30-50% across the lower deserts and 50-80%
across the higher terrain areas. Winds will remain fairly light
most of the time, with the exception being some enhanced afternoon
upslope breeziness as well as any thunderstorm activity resulting
in strong and erratic winds. Slightly cooler conditions as we
head into the week with daily readings dropping closer to normal.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Excessive Heat Warning until 8 PM PDT this evening for CAZ562-
     563-566-567.

&&

DISCUSSION...Hodges
AVIATION...AJ
FIRE WEATHER...Feldkircher

Special Weather Statement
National Weather Service Phoenix AZ
810 PM MST Sun Jul 17 2022

AZZ543-544-546-548-549-180400-
Fountain Hills/East Mesa AZ-Scottsdale/Paradise Valley AZ-
East Valley AZ-Central Phoenix AZ-North Phoenix/Glendale AZ-
810 PM MST Sun Jul 17 2022

...A strong thunderstorm will impact portions of Maricopa County
through 900 PM MST...

At 810 PM MST, Doppler radar was tracking a strong thunderstorm over
Falcon Field Airport, or over Mesa, moving west at 25 mph.

HAZARD...Wind gusts up to 50 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Phoenix, Mesa, Scottsdale, Gilbert, Tempe, Paradise Valley, East
Mesa, Mesa Riverview Mall, Tempe Marketplace, Papago Park, Piestewa
Peak Park, Arizona Mills Mall, Falcon Field Airport, Salt River
Indian Community, Downtown Mesa, South Phoenix, Superstition Springs
Mall, Downtown Phoenix, Downtown Scottsdale and Arizona State
University.

This includes the following highways...
AZ Interstate 10 between mile markers 145 and 156.
AZ Interstate 17 between mile markers 195 and 198.
AZ Route 51 between mile markers 1 and 13.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3348 11162 3337 11166 3337 11212 3365 11203
TIME...MOT...LOC 0310Z 104DEG 21KT 3345 11173

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH

18

Special Weather Statement
National Weather Service Phoenix AZ
820 PM MST Sun Jul 17 2022

AZZ547-556-558-562-563-180400-
Southeast Gila County AZ-Tonto Basin AZ-Globe/Miami AZ-
Rio Verde/Salt River AZ-Pinal/Superstition Mountains AZ-
820 PM MST Sun Jul 17 2022

...A strong thunderstorm will impact portions of Gila and Maricopa
Counties through 900 PM MST...

At 819 PM MST, Doppler radar was tracking a strong thunderstorm 13
miles north of Claypool, or 14 miles east of Roosevelt, moving west
at 20 mph.

HAZARD...Wind gusts up to 50 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Roosevelt, Roosevelt Dam, Tonto National Monument and Roosevelt
Estates.

This includes AZ Route 188 between mile markers 225 and 247.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

If on or near Lake Roosevelt, get out of the water and move indoors
or inside a vehicle. Remember, lightning can strike out to 10 miles
from the parent thunderstorm. If you can hear thunder, you are close
enough to be struck by lightning. Move to safe shelter now! Do not
be caught on the water in a thunderstorm.

&&

LAT...LON 3379 11113 3376 11099 3364 11092 3368 11084
      3365 11078 3353 11079 3349 11120 3383 11119
TIME...MOT...LOC 0319Z 091DEG 18KT 3362 11088

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH

18