Mesoscale Discussion 1145

Issued

Jul 3, 2021, 4:21 PM MST (23:21 UTC)

Expired

Jul 3, 2021, 6:45 PM MST

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

County Maricopa County, AZ

The Phoenix radar (KIWA), 93 km from the middle of the area, began a volume at 23:22 UTC, the scan nearest the moment this went out.

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831 
ACUS11 KWNS 032321
SWOMCD
SPC MCD 032321 
AZZ000-040145-

Mesoscale Discussion 1145
NWS Storm Prediction Center Norman OK
0621 PM CDT Sat Jul 03 2021

Areas affected...Parts of central Arizona including the Greater
Phoenix  Metropolitan area

Concerning...Severe potential...Watch unlikely 

Valid 032321Z - 040145Z

Probability of Watch Issuance...20 percent

SUMMARY...Thunderstorms with increasingly strong surface gusts and
blowing dust may develop off the Mogollon Rim into the lower deserts
of central Arizona, including the Greater Phoenix metro area, by 6-8
PM MST.

DISCUSSION...Destabilization and orographic forcing for ascent have
been sufficient to contribute to initiation of considerable
thunderstorm development along the Mogollon Rim.  Activity is well
underway to the northwest of the Greater Phoenix metro area, where
consolidating outflow is already slowly beginning to advance
south-southwest of the higher terrain.  This probably is being aided
by the downward transfer of weak to modest northerly to easterly
flow in the 700-500 mb layer.  However, southerly high-level flow is
allowing for anvil level cloud cover and precipitation to trail to
the north of developing outflow, and strong differential heating to
the south might by a more prominent factor allowing for propagation
of storms and outflow toward the lower deserts.

Newer thunderstorm development is also ongoing along the Mogollon
Rim to the northeast of Phoenix, and consolidating outflows may
begin to advance off the higher toward the metropolitan area during
the next few hours.  The boundary layer across the lower deserts has
become deeply mixed, with forecast soundings suggesting surface
temperatures around 100F and dew points in the lower 60s supportive
of CAPE up to 1000+ J/kg.  This probably will be sufficient to
support continuing and perhaps intensifying thunderstorm development
along the advancing outflow, which could also strengthen and be
accompanied by increasing strong surface gusts and blowing dust by
01-03Z.

..Kerr/Hart.. 07/03/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...FGZ...PSR...VEF...

LAT...LON   34271295 34061247 34071204 34011162 33541100 33011171
            32951248 33181310 33901353 34401333 34271295

Mesoscale Discussions in Arizona, 2021Every mesoscale discussion in 2021

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.