754 FXUS65 KPSR 011957 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 1257 PM MST Fri Aug 1 2025 .UPDATE...Updated Short Term Discussion... && .KEY MESSAGES... - Hot temperatures with lower desert highs of around or just over 110 degrees will continue to persist with at least widespread Moderate HeatRisk each day. - Extreme Heat Warnings with areas of Major HeatRisk will affect portions of south-central AZ through Saturday. - Another more widespread Extreme Heat episode is expected mid to late next week, with record high temperatures possible along with Major to locally Extreme HeatRisk. - Overall dry conditions will prevail for much of the area with limited chances of showers and storms mainly over eastern Arizona today and possibly again early next week. && .SHORT TERM /Today through Saturday/... Early afternoon water vapor satellite imagery, similar to the last several days, shows substantial dry air in the mid to upper- levels byproduct of the westerly flow aloft in place from a longwave trough located off the Pacific Northwest and the subtropical high centered near the international border. Some low- level moisture, evidenced by PWATs near 1-1.2" across the southeastern quadrant of Arizona, will continue to support isolated to widely scattered storm activity across the eastern and southern third of the state this afternoon. Drier air moving in from the west will continue to gradually erode the lingering low- level moisture in place through the rest of today and thus no storm activity is expected across the lower deserts. Heading into Saturday, most of the low-level moisture will be mostly scoured out such that storm chances are expected to be mostly eliminated across most of Arizona as PWATs once again drop to well-below normal levels of well under one inch. As the aforementioned subtropical high strengthens through Saturday with 500 mb height fields peaking at 596-598dm, temperatures will be on a slight increase. Afternoon high temperatures today will peak at between 108-113 degrees and rise another degree or two on Saturday across the lower deserts. NBM probabilities show an 80% chance of tying and at least a 50% chance of breaking the record high of 113 degrees in Phoenix on Saturday. These high temperatures in combination with above normal early morning low temperatures both this morning and once again on Saturday morning will result in areas of Major HeatRisk across the south-central Arizona lower deserts and thus an Extreme Heat Warning is in effect through early Saturday evening. Thus, anyone scheduling outdoor activities are urged to take the necessary precautions to avoid any heat-related illnesses. && .LONG TERM /Sunday through Friday/... The main forecast concern in the long term will be the building heat during the middle to latter part of next week with record temperatures likely to occur. Initially, we will get a little bit of a break by Sunday with overnight lows improving due to the drier air and H5 heights lowering a smidge. This should drop lows back to around normal which would be as much as five degrees cooler in Phoenix compared to the early morning lows of both today and Saturday. Daytime highs are still forecast to top out between 108-112 degrees each day through early next week, but when combined with the cooler overnight lows it will drop the entire area into the Moderate HeatRisk category. The center of the ridge is eventually expected to shift eastward into New Mexico Monday into Tuesday allowing for some weak south southeasterly flow into Arizona. Guidance does show some moisture return into the area during this time, but PWATs are only shown to max out at around 1.1" with low level mixing ratios at most between 7-9 g/kg. This may bring a few isolated showers or a weak thunderstorm already on Monday, but chances seem a bit better (but still limited) on Tuesday with a bit better moisture. The ridge is also forecast to strengthen early next week with H5 heights rising to between 598-601dm over eastern portions of the region by Tuesday or Wednesday. The likely strength of this ridge puts it into record territory for the climatological period over the entire region by next Wednesday and Thursday. Temperatures should quickly respond by climbing to at least 112-116 degrees by Wednesday and potentially a couple degree hotter for next Thursday and Friday. There is still some uncertainty with how much moisture will be around during the latter half of next week, but in reality it seems unlikely to be enough to stop us from seeing an Extreme Heat event. An Extreme Heat Watch has been issued for south-central and portions of eastern Arizona for Tuesday-Friday and across southwest Arizona and southeast California for Wednesday-Friday. Widespread Major HeatRisk with localized Extreme HeatRisk is seen developing by next Wednesday, potentially lasting through around next Friday. NBM deterministic forecast temperatures are still coming in on the lower end of potential guidance, so there is definitely room for forecast temperatures to go higher. In fact, the NBM 75th percentile shows readings up to 120 degrees for KPHX next Thursday and Friday. The hottest Phoenix has ever recorded in the month of August was 117 degrees which has happened 4 times (2011, 2015, 2020, and 2023). Overnight lows are also expected to climb back to around the 90 degree mark for the Phoenix metro with a night or two later next week potentially in the mid 90s. && .AVIATION...Updated at 1705Z. South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation weather concerns are expected through the TAF period. Winds will follow familiar diurnal trends, with typical afternoon/evening breeziness around 15-20 kts. The transition to a W`rly component will be slower than usual as winds will likely fluctuate 150v220 between 18-21Z. Outside of a FEW distant CU bases around 10 kft, skies will remain mostly clear. Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation weather concerns are expected through the next 24 hours under clear skies. Winds will continue to follow diurnal trends, with afternoon gusts at KBLH around 20-25 kts. KIPL may see some occasional gusts this evening in conjunction with the W`rly shift. && .FIRE WEATHER... Drying conditions will occur today into the weekend with only a limited chance for a few showers and isolated thunderstorms over the eastern Arizona higher terrain through this evening. Afternoon MinRHs today will still be between 10-15% across the lower deserts to 15-20% in higher terrain areas before dropping further into the weekend. Winds will generally follow diurnal tendencies with typical afternoon upslope gustiness. Temperatures will remain above normal with lower desert highs mostly between 108-114 degrees. Overall dry and hot conditions will continue to prevail into next week with only very limited mostly high terrain chances around Tuesday or Wednesday. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Extreme Heat Watch from Wednesday morning through Friday evening for AZZ530>533-535-536. Extreme Heat Warning until 8 PM MST Saturday for AZZ534-537>544- 546-548>555-559. Extreme Heat Watch from Tuesday morning through Friday evening for AZZ534-537>563. CA...Extreme Heat Watch from Wednesday morning through Friday evening for CAZ560>570. && $$ SHORT TERM...Lojero LONG TERM...Kuhlman AVIATION...RW FIRE WEATHER...Kuhlman