730 FXUS65 KPSR 081757 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 1057 AM MST Tue Jul 8 2025 .UPDATE...Updated 18z Aviation Discussion. && .KEY MESSAGES... -Strong high pressure over the region will result in well above normal temperatures through midweek with afternoon highs forecast to reach and exceed 115 degrees across many of the lower desert communities Wednesday -The heat will result in widespread Major HeatRisk with Extreme Warnings in effect for much of the region today through Thursday -Slightly cooler temperatures expected by the end of the week through this weekend, but remaining above normal -Thunderstorm activity will continue to be limited to the Arizona high terrain and southeast Arizona during the next several days && .SHORT TERM /TODAY THROUGH WEDNESDAY/... Latest water vapor satellite imagery as well as objective analysis show the subtropical high situated across eastern AZ, with 500 mb heights around 595dm, while a cutoff low pressure system remains situated off the central CA coast. The cutoff low is forecast to weaken throughout the day today, which will allow the subtropical high to expand westward and strengthen even more as 500 mb heights increment to 596-598dm. As a result of the strengthening high, afternoon high temperatures today are forecast to be 2-4 degrees warmer than yesterday with many of the lower desert locations ranging between 109-113 degrees. The hottest locations will be over south-central AZ, where areas of Major HeatRisk will materialize and thus Extreme Heat Warnings will go into effect starting later this morning across the lower deserts of Maricopa and Pinal Counties and the San Carlos area of Gila County. As the high continues to expand westward and strengthen slightly, Wednesday is expected to be even hotter and the peak of the extreme heat episode. Many of the lower desert locations are forecast to see highs of 115+ degrees. This will result in widespread Major HeatRisk across the majority of the region and thus the areal coverage of the Extreme Heat Warning expands to include all the lower deserts as well across the higher terrain areas east of Phoenix below 4000 feet with a Heat Advisory in effect for elevations above 4000 feet. Daily record highs are likely to be challenged in both Phoenix and El Centro. In terms of thunderstorm activity, strong subsidence from the strengthening high and meager moisture will hinder the potential for any widespread activity. Any thunderstorm activity during the next couple of days will be confined mainly to the High Country, the White Mountains, and the southeastern third of AZ. && .LONG TERM /THURSDAY THROUGH MONDAY/... The subtropical high is expected to weaken slightly heading into Thursday as the energy leftover from the cutoff low migrates eastward into the Great Basin and Intermountain West Regions. This will result in a slight decrease in the heights aloft and thus afternoon high temperatures will be slightly cooler but still hot enough for areas of Major HeatRisk to remain in place with Extreme Heat Warnings remaining in effect for all of the lower desert communities. Heading towards the end of the week through next weekend, the high will continue to very gradually migrate westward towards the southern CA coastline and as a result heights aloft will continue to decrease slightly more. This will translate to slightly cooler temperatures, but still remain a few degrees above normal as afternoon highs across the lower deserts will average around 110 degrees, resulting in widespread Moderate HeatRisk. With the subtropical high migrating westward into southern CA towards the end of the week and weekend, the upper-level flow pattern will remain quite unfavorable for any deep moisture influx. Thus conditions are expected to remain mostly dry across much of the region, with any thunderstorm activity limited across the White Mountains through the southeastern third of AZ. As the high migrates into the southern CA coastline during the weekend, the upper-level flow is expected to turn out of the north, which will bring in even drier air with the latest EPS and GEFS showing PWATs dropping below one inch. Thus, thunderstorm activity will likely be more limited, even across the higher terrain areas. This overall dry pattern will continue into early next week before the high potentially repositions near the Four Corners by the middle to latter half of next week, which if it materializes, would be a more favorable flow pattern to advect deeper moisture into the region and reintroduce higher thunderstorm chances. && .AVIATION...Updated at 1755Z. South Central Arizona including KPHX, KIWA, KSDL, KDVT: No major aviation weather concerns will exist through the TAF period under FEW mid and high clouds. Winds will predominantly favor the W/NW through this evening. Followed by winds going light and variable during the overnight hours at KSDL and KDVT, KPHX going light and variable around sunrise, and KIWA going light southeasterly during the overnight hours. Expect gusts to around 20 kts this afternoon into the early evening. Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation weather concerns are expected through the next 24 hours under periods of FEW to at times SCT mid and high clouds. Winds will continue to vary between S/SE and SW, with extended periods of light and variable winds, particularly at KIPL. Wind speeds will generally remain AOB 10 kts, though some gusts to around 15-20 kts are possible, particularly after the switch to a SW`rly direction this evening. && .FIRE WEATHER... Generally dry conditions and above normal temperatures will persist during the next several days as lower deserts highs reach and exceed 110 degrees each day. MinRH values will generally be in the teens each day, while MaxRH values will be the lowest tonight and Wednesday night at 20-40% and then increase up to 30-50% the rest of the week for most of the area. The exception will be across Imperial and southern Yuma Counties where periodic gulf surges will result in MaxRH values in excess of 50%. The overall wind pattern will follow the familiar diurnal trends, with some afternoon/early evening breeziness. A slight uptick in the winds is expected, especially on Thursday afternoon, which may lead to locally elevated fire weather conditions in the afternoon. Very minimal rain chances will exist during the next several days with CWR <10% through at least next weekend. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Extreme Heat Warning from 10 AM Wednesday to 8 PM MST Thursday for AZZ530>533-535-536. Extreme Heat Warning until 8 PM MST Thursday for AZZ534-537>540- 542>544-546-548-550-551-553>555-559-560. Heat Advisory from 10 AM to 8 PM MST Wednesday for AZZ557-558- 563. Extreme Heat Warning from 10 AM to 8 PM MST Wednesday for AZZ541- 545-547-549-552-556-561-562. CA...Extreme Heat Warning from 10 AM Wednesday to 8 PM PDT Thursday for CAZ560>570. && $$ SHORT TERM...Lojero LONG TERM...Lojero AVIATION...Berislavich/Whittock FIRE WEATHER...Lojero/Benedict