An upper level ridge situated over much of the western United States at the end of July led to heat that resulted in several fatalities. One of these fatalities included a woman visiting from Boston who died after becoming overheated while hiking on Camelback Mountain.
Every event with a place to put it; 5 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.
An upper level ridge situated over much of the western United States at the end of July led to heat that resulted in several fatalities. One of these fatalities included a woman visiting from Boston who died after becoming overheated while hiking on Camelback Mountain. According to the Maricopa County Department of Public Health, a total of 7 heat-associated fatalities occurred 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 27, 2:47 PM MST, 2 hours 13 minutes earlier.
Area Forecast Discussion National Weather Service Phoenix AZ 247 PM MST Tue Jul 27 2021 .SYNOPSIS... Warmer and drier weather will temporarily return through Wednesday with fairly minimal storm chances mainly confined to higher terrain areas of Arizona. However, later in the week another wave of low pressure is expected to affect the region bringing a return to more widespread shower and thunderstorm activity as early as Thursday. The more active monsoon activity should persist into the weekend before a gradual decrease in shower and storm chances by early next week. && .DISCUSSION... Although the environment is notably drier than previous days, PWATs are still near to slightly above normal and sufficient for efficient rain-producing storms. The synoptic setup this afternoon is that of a somewhat more traditional monsoon with south to southeast flow across the region. The monsoon high is a bit further north than usual over parts of NE/WY/CO, but it is still very broad and the primary driver of the steering pattern. So far this afternoon scatter cumulus developed across the region with isolated storms developing over terrain features across AZ, but with more scattered coverage evident in southeast AZ. 12Z HREF and individual hi-res models suggest storms will mostly remain anchored to high terrain areas through the rest of the afternoon with limited development over lower elevations. NBM PoPs in the Phoenix area are less than 5%. MLCAPE is modest, upwards of 500-1000 J/kg on objective analysis, so there is potential for strong updrafts and even marginally severe storms in southeast AZ where lapse rates are steeper. DCAPE is also moderately high with values analyzed around 1000-1500 J/kg, so there is potential for strong downbursts. Hi-res models show good agreement on outflow winds progressing north or northwestward through portions of Pinal and Maricopa counties this evening, but likely lacking reinforcement and losing strength as boundaries progress into the local CWA. Still HREF has a 40-60% chance for outflow winds in excess of 35 mph through central Pinal county and along I-8 in Maricopa county. This may lead to localized blowing dust, but the recent rains may limit the full dust potential. With weak steering flow, around 10-15 kts, any isolated storm that anchors over an area for an extended period of time will be capable of localized flash flooding in addition to the winds and lightning. Showers and storms are expected to dissipate this evening with the loss of heating. Drying conditions are expected to continue through Wednesday, likely limiting storm development to far southeast Arizona and along the Mogollon Rim. HREF members mostly point toward Wednesday as seeing less activity than today. Temperatures will continue to warm during the middle part of this week, especially across the western deserts with more substantial loss of boundary layer moisture. Forecast NBM highs warm to around 110 degrees across southeast California on Wednesday with 103-105 degrees in the Phoenix area. Readings on Thursday should tick up another degree or two across the western deserts before the next round of monsoon moisture and activity by Friday. .PREVIOUS DISCUSSION... Model ensembles remain in good agreement showing another active monsoon period later this week, but the timing is still somewhat uncertain. With the subtropical ridge shifting over the Central Plains, the large cyclonic circulation over the Gulf of Mexico is seen slowly shifting westward over the next several days. Broad synoptic scale ascent will begin entering our region from the east as early as Thursday, but more so on Friday and Saturday. Storm activity is likely to increase on Thursday, especially over the high terrain of eastern and southeast Arizona. WPC has added a slight risk ERO for parts The lower deserts on Thursday will still be under marginal moisture, but any substantial colliding outflows into the south- central Arizona deserts may be enough for storms to develop over the deserts Thursday evening. As the easterly wave/inverted trough continues to track westward on Friday into Saturday, deeper moisture will overspread the rest of the lower deserts likely leading to fairly widespread chances for showers and storms. This next disturbance is nowhere near the level of what we just experienced, but more like a typical monsoon easterly wave commonly seen during active monsoon seasons. NBM PoPs reflect the expected increase in monsoon storm activity later this week with PoPs of 30-40% over the Phoenix area late Thursday and then widespread 30-50% PoPs over the lower deserts for Friday and at least through Saturday. PoPs over the Arizona high terrain also increase to 60-80% during the period. A bit lower moisture levels compared to the last weather disturbance point toward strong winds as more of a threat with this upcoming disturbance versus the last one. Heavy rainfall and localized flooding will also be a possibility, but probably to a lesser degree than what we saw late last week and over the weekend. However, existing wet soils from the recent heavy rains will make any additional heavy rainfall more problematic than normal. Model uncertainty increases into early next week with the EPS favoring a period of drier conditions, while the GEFS holds onto better moisture and thus continued monsoon storm chances. The NBM reflects the decreasing storm chances with PoPs gradually lowering Sunday through Tuesday. After a few days of below normal temperatures starting Friday, temperatures are likely to begin an upward climb by Sunday or Monday. NBM highs across the western deserts do return to normal as early as Sunday, while continued below normal temperatures look more likely for the Arizona deserts through early next week. && .AVIATION...Updated at 1738Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Mostly clear skies with light east winds will prevail into the early/mid afternoon. The switch to light westerly winds may be disjointed with some measure of variability during the mid afternoon. Storms are forecast to develop in far southern AZ this afternoon pushing an outflow boundary towards the Phoenix metro. Confidence is moderate that this may only be a subtle wind shift from westerly to SSW with minimal to no gusts. There's even some chance (~50%) outflow winds never even enter visual ranges before the typical nocturnal switch back to easterly around midnight. Light easterly winds are then expected to continue into Wednesday morning, then a rather typical switch to westerly winds can then be expected during the early afternoon hours. Convective activity on Wednesday afternoon/evening is expected to remain well to the north and of the Phx area (along the Rim/White Mtns), with just an outside chance of some weak outflows working their way SE-ward into the Phx area during the evening hours on Wed. Southeast California/Southwest Arizona including KIPL and KBLH: Under occasional cirrus decks, wind will be light and primarily favor southerly directions (outside of a period of light westerly Sundowner winds at KIPL this evening). Extended periods of variable directions should be expected as well. && .FIRE WEATHER... Friday through Tuesday: A weather disturbance is expected to track into the region late in the week. This should bring more widespread shower and storms by Friday and likely lasting into the weekend. Thunderstorm chances in the eastern districts increase better than 50% Thursday afternoon into Friday morning with a returning threat of heavy rainfall and flash flooding. These heightened storm chances spread westward for Friday and Saturday. A likely downtrend in monsoon activity is expected late in the period, but isolated storms may continue to impact the high terrain of eastern districts. Temperatures will range from near to slightly below normals the bulk of the period. Minimum afternoon humidity values will range from 25-45% through the weekend before falling back to 15-30% early next week. Overnight recovery will be mostly good to excellent in a 40-80% range. Apart from thunderstorms, winds will favor typical daily upslope/drainage patterns. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && DISCUSSION...Benedict PREVIOUS DISCUSSION...Kuhlman AVIATION...Percha/18 FIRE WEATHER...Benedict/Kuhlman
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
339 PM MST TUE JUL 27 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1005 AM FLASH FLOOD 6 N DEER VALLEY 33.76N 112.11W
07/25/2021 MARICOPA AZ MESONET
*** DELAYED REPORT *** FCDMC SONORAN WASH
#65907 REACHED AND EXCEEDED BANK FULL WITH
FLOOD WATERS LIKELY IMPACTING UNBRIDGED
CROSSING AT DIXILETA DR. ONE MILE DOWNSTREAM
OF GAUGE.
&&
GL/SBPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
409 PM MST TUE JUL 27 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0230 PM FLASH FLOOD 1 SE GLOBE 33.38N 110.77W
07/27/2021 GILA AZ TRAINED SPOTTER
FLOW IN PINAL CREEK MADE BEER TREE CROSSING
ROAD IMPASSABLE.
&&
AJThe national radar mosaic for the moment the first event began.
5 heat. Local standard time, as filed.
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.
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.
One direct fatality was reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
A 31-year-old woman visiting from Boston went hiking with a man on Echo Canyon Trail on Camelback Mountain around 1PM MST. The woman became overheated about halfway up the trail and decided to turn around and go back down, while the man continued up the trail. The woman was later discovered and pronounced dead near a home next to the mountain after she was believed to be seeking help. The man and woman were reportedly hiking without any water.
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.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
| Event | Date | Age | Sex | Where | Kind |
|---|---|---|---|---|---|
| Heat, Central Phoenix | 2021-07-27 | Unknown | Indirect | ||
| Heat, Central Phoenix | 2021-07-27 | Unknown | Indirect | ||
| Heat, Central Phoenix | 2021-07-28 | Unknown | Indirect | ||
| Heat, Central Phoenix | 2021-07-28 | Unknown | Indirect | ||
| Heat, Central Phoenix | 2021-07-29 | Unknown | Direct | ||
| Heat, Scottsdale/Paradise Valley | 2021-07-30 | 31 | Female | Outside/Open Areas | Direct |
| Heat, North Phoenix/Glendale | 2021-07-30 | Unknown | Indirect |
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2021Every state in 2021This day in weather historyWarnings in Arizona, July 2021
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: 1067092, 1067093, 1067094, 1067137, 1067096.