Dust Storm Warning 7, NWS Phoenix, AZ

Area Forecast Discussion
National Weather Service Phoenix AZ
415 PM MST Sat Jul 3 2021

.UPDATE...
Updated Aviation

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.SYNOPSIS...
Chances for showers and thunderstorms will continue through this
weekend with decreasing chances by Monday followed by little chance
for the middle of next week. Storms will be common over the higher
terrain and more isolated on the lower elevations. Gusty winds with
localized blowing dust and localized heavy rainfall capable of
producing flash flooding will be the main impacts. Although a
general drying and warming trend with above normal temperatures is
expected next week across most of the region, isolated storm chances
are likely to persist over the eastern Arizona high terrain.

&&

.DISCUSSION...
Latest signals from observational and model data point to an active
evening across south-central Arizona. The atmosphere is
exceptionally moist today with PWATs ranging from 1.5 to 2.0 inches,
placing it in the 95th percentile of climatology for the day. Latest
RAP streamline analysis depicts the inverted trough across
southeastern Arizona, situated between two anticyclones, one across
western Texas and another across northern Arizona. The resulting
mean layer flow is out of the southeast, which will be favorable to
maintain the deeper moisture. Surface dewpoints have only dropped a
few degrees this afternoon and remain in the lower 60s.

Convection has already initiated along the Mogollon Rim, and across
portions of southeastern Arizona near a well-defined vort max.
Morning KPHX sounding indicated relatively strong easterly flow of
30 kt at 600 mb, which will help to steer activity into south-
central Arizona this evening. Consensus from the CAMs including the
HRRR suggests an outflow boundary from storms in the higher terrain
will also provide the lift necessary to overcome any low-level CIN
in the Valley, while also allowing new cells to propagate rapidly
into the deserts south and west of Phoenix. Consequently, PoPs were
increased to around 50 percent in the Phoenix area, and as high as
70 percent near Casa Grande.

HREF ensemble max gusts are around 50 mph in the strongest storms,
and this is not entirely surprising given the anomalously rich low-
level moisture and subsequent dearth of DCAPE. Nevertheless, strong
wind gusts will still be possible in the vicinity of the outflow
boundary as it descends into the lower deserts. However, the greater
threat will likely be the potential for flash flooding, particularly
across the higher terrain of Gila County and within the recent burn
scars. Latest guidance suggests rain rates could reach 1-3 in/hr in
the strongest cells.

&&

.PREVIOUS DISCUSSION...
A shift in the pattern is expected to begin on Sunday with the drier
southerly flow across the western deserts to begin expanding
eastward late in the day as well as drier northwesterly mid level
flow beginning in the afternoon. Abundant boundary layer moisture
will still be present over much of the region on Sunday, but the
drying aloft will begin to have a noticeable effect on storm
activity, especially across the lower deserts. Showers and storms
will again be likely across the eastern Arizona high terrain Sunday
afternoon, but they will likely have a more difficult time
maintaining their westward push into the south-central Arizona
deserts. Can't rule out some isolated to scattered storms affecting
the Phoenix area Sunday, but chances mostly drop into a 15-20% range.

The westerly drying will continue early next week, likely ending
storm chances completely across the lower deserts as early as
Monday. Afternoon surface dew points are forecast to drop into the
40s across the western deserts on Monday and then across the south-
central Arizona deserts on Tuesday. The upper level ridge center is
also seen shifting into Nevada while also strengthening, likely
leading to H5 heights increasing to 592-595dm across the Desert
Southwest. The drying boundary layer and increased heights aloft
should push daytime highs to around 110 degrees in the Phoenix area
to 110-113 degrees across the western deserts. So far NBM guidance
has been keeping temperatures just below excessive heat levels for
next week, but if the upper end of guidance proves true then some
heat products may be needed. After a few days of likely minimal
monsoon storm activity confined to the eastern Arizona high terrain,
there are signs of some moisture return and expansion into the lower
deserts at some point later next week. However, the flow pattern
through next weekend does not look very conducive for deep moisture
advection, likely limiting storm chances across the lower deserts.

&&

.AVIATION...Updated at 2315Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
HREF output shows gusty N/NE winds moving through the metro between
01Z-04Z with greater than a 70% chance of gusts above 30kt. There is
also multiple outflows moving in from the south which could create
collisions and erratic directions. NBM probabilities of storms at
any location is better than 50% with HREF neighborhood probabilities
about the same. Kept VCTS along outflow, then VCSH and variable
winds later this evening. Some dust could be picked up along
outflows as well. Cigs 8K-12K ft AGL are forecast by NBM this
evening and overnight. NBM has nearly 30% chance of rain through
Sunday morning, but cut off mention shortly after midnight. NBM
shows west winds and storm chances less than 15% Sunday afternoon
and evening.

Southeast California/Southwest Arizona including KIPL and KBLH:
Southeast to southwest winds are forecast during the periods with
speeds mostly below 12kt. HREF output shows a weakening outflow
boundary hitting KBLH later tonight though probabilities of greater
than 30kt is 10% or less. Cloud heights will be 12K ft and above
with NBM showing less coverage tomorrow.

&&

.FIRE WEATHER...
Tuesday through Saturday:
Moisture will decrease gradually through the midweek period, which
will generally confine the threat of storms to eastern Arizona. A
return of deeper moisture looks possible late next week with storm
chances potentially increasing and expanding westward across
Arizona. Temperatures for the bulk of the period will run a few to
several degrees above normal. Min RH values will drop into the 10-
15% range over southeast California and southwest Arizona and 15-25%
range over south central Arizona with the highest values over the
higher terrain north and east of Phoenix. Max RHs will recover into
the 30-45% range for most locations. Apart from thunderstorms, wind
patterns will follow diurnal patterns.

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

&&

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

&&

DISCUSSION...Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...18
FIRE WEATHER...Hirsch/Hopper/Kuhlman

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
543 PM MST SAT JUL 3 2021

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

0538 PM     DUST STORM       1 WSW WITTMANN          33.77N 112.54W
07/03/2021                   MARICOPA           AZ   TRAINED SPOTTER

            LESS THAN 1.4 MILE VISIBILITY.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
544 PM MST SAT JUL 3 2021

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

0532 PM     DUST STORM       5 WNW SUN LAKES         33.25N 111.95W
07/03/2021                   MARICOPA           AZ   PUBLIC

            REPORTS OF LOCAL 1/4 MILE VISIBILITY NEAR
            I-10 AND HWY 347.

&&

Special Weather Statement
National Weather Service Phoenix AZ
620 PM MST Sat Jul 3 2021

AZZ537-540>544-546>550-040200-
South Mountain/Ahwatukee AZ-Fountain Hills/East Mesa AZ-
Scottsdale/Paradise Valley AZ-Buckeye/Avondale AZ-
Cave Creek/New River AZ-East Valley AZ-Central Phoenix AZ-
Deer Valley AZ-Northwest Valley AZ-Rio Verde/Salt River AZ-
North Phoenix/Glendale AZ-
620 PM MST Sat Jul 3 2021

...SIGNIFICANT WEATHER ADVISORY FOR MARICOPA COUNTY UNTIL 700 PM
MST...

At 619 PM MST, Doppler radar was tracking several strong
thunderstorms across the Phoenix metro area. Movement was south at 5
mph.

Winds in excess of 40 mph will be possible with these storms.

Locations impacted include...
Phoenix, Mesa, Chandler, Glendale, Scottsdale, Gilbert, Tempe,
Peoria, Surprise, Avondale, Goodyear, Buckeye, El Mirage, Fountain
Hills, Paradise Valley, Tolleson, Youngtown, Waddell, Laveen and
Cashion.

This includes the following highways...
AZ Interstate 10 between mile markers 116 and 159.
AZ Interstate 17 between mile markers 195 and 225.
AZ Route 51 between mile markers 1 and 15.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

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LAT...LON 3337 11258 3331 11210 3334 11167 3355 11163
      3378 11162 3382 11212 3380 11256 3355 11260
TIME...MOT...LOC 0119Z 002DEG 5KT 3357 11243 3353 11211 3355 11177

SDB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
621 PM MST SAT JUL 3 2021

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

0550 PM     TSTM WND GST     5 NE SURPRISE           33.71N 112.28W
07/03/2021  M39 MPH          MARICOPA           AZ   PUBLIC

            SPOTTER REPORTED 2 SMALL TREES DOWN (4-8
            INCH DIAMETER). NEARBY OBSERVATION OF 39 MPH
            WIND GUST.

&&

Special Weather Statement
National Weather Service Phoenix AZ
631 PM MST Sat Jul 3 2021

AZZ547>549-551>553-555>558-040215-
Fountain Hills/East Mesa AZ-Mazatzal Mountains AZ-Tonto Basin AZ-
Northwest Pinal County AZ-East Valley AZ-
Southeast Valley/Queen Creek AZ-Apache Junction/Gold Canyon AZ-
Superior AZ-Rio Verde/Salt River AZ-Pinal/Superstition Mountains AZ-
631 PM MST Sat Jul 3 2021

...SIGNIFICANT WEATHER ADVISORY FOR GILA...MARICOPA AND PINAL
COUNTIES UNTIL 715 PM MST...

At 630 PM MST, Doppler radar was tracking strong thunderstorms along
a line extending from near Ballantine Trailhead to Canyon Lake to 6
miles north of Queen Valley. These storms were nearly stationary.

Winds in excess of 40 mph will be possible with these storms.

Locations impacted include...
Mesa, Apache Junction, Superior, Gold Canyon, Sugarloaf Mountain,
Sycamore Creek, Ballantine Trailhead, Roosevelt, Round Valley,
Sunflower, Queen Creek, Gold Camp, Roosevelt Dam, Lost Dutchman State
Park, Goldfield, Usery Mountain Park, Florence Junction, Queen
Valley, Canyon Lake and Superstition Mountains.

This includes the following highways...
US Highway 60 between mile markers 189 and 231, and near mile marker
233.
AZ Route 87 between mile markers 192 and 227.
AZ Route 202 between mile markers 25 and 36.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3372 11115 3343 11099 3321 11108 3315 11135
      3330 11168 3385 11167 3387 11165 3390 11167
      3395 11142
TIME...MOT...LOC 0130Z 053DEG 3KT 3376 11156 3357 11144 3340 11128

SDB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
638 PM MST SAT JUL 3 2021

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

0615 PM     TSTM WND GST     2 ENE SUN CITY WEST     33.68N 112.34W
07/03/2021  M39 MPH          MARICOPA           AZ   TRAINED SPOTTER

            ALSO OVER 1/2 INCH OF RAIN IN 30 MINUTES.

&&