The Desert Southwest continued to remain under the influence of an upper level ridge of high pressure during the July 6-10th time period. As a result, high temperatures in Phoenix continued to reach or exceed 110 degrees each day with the 6th reaching a high of 115 degrees.
Every event with a place to put it; 19 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
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.
The episode as NWS PSR wrote it up.
The Desert Southwest continued to remain under the influence of an upper level ridge of high pressure during the July 6-10th time period. As a result, high temperatures in Phoenix continued to reach or exceed 110 degrees each day with the 6th reaching a high of 115 degrees. According to the Maricopa County Department of Public Health, 25 heat-associated fatalities occurred during this time. One heat-associated fatality also occurred in southern Gila County during this time.
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 5, 10:13 PM MST, 1 hour 47 minutes earlier.
Area Forecast Discussion
National Weather Service Phoenix AZ
1013 PM MST Wed Jul 5 2023
.UPDATE...
Updated Aviation discussion.
&&
.SYNOPSIS...
High pressure will continue to predominate the overall weather
pattern across the Desert Southwest into next week. High
temperatures of around 110 degrees are expected across the lower
deserts through the weekend. An Excessive Heat Warning is in
effect for the south-central Arizona lower deserts through Friday.
Dry and breezy conditions each afternoon will result in elevated
fire weather concerns. For the first half of next week, even
hotter conditions are likely with enough monsoon moisture moving
into southeastern Arizona for some chances for isolated high
terrain thunderstorms.
&&
.DISCUSSION...
Latest water vapor imagery and streamline analysis reveal a well-
defined anticyclone across southern California with the ridge axis
extending eastward into southeastern Arizona. This is resulting
in a continuation of the above normal temperatures, clear skies
and below normal dewpoints across the Desert Southwest. Latest
ACARS soundings indicate a pronounced subsidence inversion around
500 mb with PWATs around 0.7 inches near Phoenix.
Over the next few days, the aforementioned anticyclone will
become repositioned across New Mexico, resulting in a dry
southwesterly flow and continued well above normal temperatures.
Further west, latest models indicate a subtropical area of low
pressure will move northeastward towards the Baja Peninsula and
into southern California, suppressing the positive height
anomalies to the south and east. This will result in somewhat
cooler conditions across southeastern California and an increase
in uncertainty further east across the lower deserts of Arizona.
Current Excessive Heat Warning for south-central Arizona goes
through Friday and for now this will not be extended into the
weekend. However, latest trends in the grand ensemble suggest
another significant warming trend next week.
Latest ECMWF ensemble shows a concerning trend with an
anomalously strong subtropical ridge strengthening and meandering
to the north and west. Given the inherent uncertainty further out
in time, positive height anomalies of +2 standard deviations from
an ensemble system suggest the potential for near record
temperatures next week, with high temperatures likely reaching
113-119 degrees each day in Phoenix. A slight increase in
humidity will also translate into well above normal low
temperatures, which will inhibit overnight recovery and exacerbate
the Heat Risk.
One thing to consider is the longevity of the heat wave and the
cumulative effects on the body. There have been 5 consecutive
days so far of 110+ degrees in Phoenix and the record of 18
straight days set in June 1974 could be challenged. Although it is
unlikely the all-time daily record of 122 degrees will be reached
in Phoenix, latest NBM does indicate roughly a 10 percent chance
of reaching this value at Phoenix Sky Harbor Airport sometime next
week. Meanwhile, latest trends in the ensembles do suggest a
gradual increase in moisture emanating from Mexico next week as
well. However, low-level mixing ratios and subsequent instability
will likely remain inadequate for even isolated convection, except
across the higher terrain of eastern and southeastern Arizona.
&&
.AVIATION...Updated at 0513Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT and
Southeast California/Southwest Arizona including KIPL and KBLH:
Clear skies can be expected through Thursday night. Winds will
continue to follow familiar warm season diurnal patterns during
that same time as well. For the Greater Phoenix area, this will
mean overnight hours with light and variable winds initially
favoring west before transitioning to light downvalley/drainage
winds (favoring east component). This will be followed by a
resumption of afternoon westerly winds with gusts generally
15-25kts. For KIPL, this will mean nighttime winds favoring
westerly directions and daytime winds favoring southeasterly
directions. Of note for Thursday, southwest and westerly
breeziness develops by late afternoon at KIPL.
&&
.FIRE WEATHER...
Hot, dry, and breezy conditions will persist for the next several
days. High temperatures will continue to run several degrees
above normal across the central and eastern Arizona with minimum
relative humidity falling below 15 percent each afternoon.
Winds will oftentimes be breezy during the afternoon and early
evening hours with gusts reaching 20-25 mph across much of the
area. These dry and breezy conditions combined with the extreme
heat will result in elevated fire weather conditions for much of
area this week and into this weekend. Overnight moisture recovery
will range from poor to fair each night. For next week, even
hotter conditions are expected with a gradual increase in moisture
likely leading to isolated thunderstorm chances over the eastern
Arizona high terrain.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Friday for AZZ534-537>544-
546-548>551-553>555-559.
CA...None.
&&
DISCUSSION...Hirsch
AVIATION...AJ
FIRE WEATHER...KuhlmanThe national radar mosaic for the moment the first event began.
18 excessive heat, 1 heat. Local standard time, as filed.
Fifteen heat-associated fatalities (5 direct and 10 indirect) were reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
One indirect fatality was reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
Two indirect fatalities were reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
Seven indirect fatalities were reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
One direct fatality was reported in the San Carlos area, with their details, such as age, gender, circumstances, and exact location unavailable.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2023Every state in 2023This day in weather historyWarnings in Arizona, July 2023
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: 1210470, 1210472, 1210476, 1210477, 1217773, 1217774, 1217775, 1217776, 1217777, 1217778, 1217779, 1217783, 1217784, 1217785, 1217786, 1217787, 1217788, 1217789, 1210480.