FXUS65 KPSR 220909 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 209 AM MST Sat Aug 22 2026 .KEY MESSAGES... - High temperatures reach or exceed 110 degrees nearly every day through the next week and will be within a few degrees of daily records, while morning lows remain unusually warm. - Extreme Heat Warnings are in effect through Friday evening with daily Major to Extreme HeatRisk. - Thunderstorms will primarily favor higher terrain areas through early next week, with drier and less favorable conditions next week. && .SHORT TERM /TODAY THROUGH MONDAY/... Extreme heat will be the primary weather hazard through the short, and long, term forecast. Early morning objective analysis shows a 596dm high pressure centered over CO/NM. Models show that this high will slowly progress eastward through the beginning of next week. Despite the center of the high moving away from our region, H5 heights over our region will remain in a 594-597dm range. With heights of this magnitude, the NBM continues to show afternoon highs (morning lows) of 110-116 (83-91) degrees across the lower deserts and 100-110 (70-80) degrees across the higher terrain areas. Temperatures of this magnitude are 5-8 degrees above daily normals and some locations could tie or break their daily records (see Climate section below). These temperatures will lead to widespread high-end Moderate to Major Heat Risk across much of the CWA and therefor the Extreme Heat Warning remains in effect. The best thunderstorm chances will exist across the higher terrain areas through the beginning of next week with only slight chances for some isolated activity across the lower deserts. Thunderstorm chances across the lower deserts for this afternoon are around 10-20%. While some hi-res models (HRRR and RRFS) are trying to pick up on some more scattered activity across south- central AZ (including the Phoenix Metro) they are likely overdoing the coverage. Models show limited moisture today (PWATs of 1.0-1.3"), mixing ratios only around 6-7 g/kg, MUCAPE values less then 500 J/kg, and around 25-50 J/kg of CIN. The hi- res models showing scattered to widespread activity for this evening are likely picking up on some upper-level divergence and colliding outflows. While there will likely be multiple outflows moving off the higher terrain this evening not much activity (other than some isolated showers and maybe a few isolated storms) is expected even if they do collide due to all the limiting factors mentioned earlier. Strong to locally severe wind gusts and areas of blowing dust will be the primary hazard with any storm this afternoon and evening, with high DCAPE values (1800-2000 J/kg). Models are in decent agreement that there will be a slight increase in moisture on Sunday and Monday (PWATs increase to around 1.1-1.6" across the area) with the highest moisture expectedon Monday. Instability will be about the same on Sunday as today, but will increase to around 1000-1500 J/kg on Monday. Additionally, mixing rations will increase to around 10 g/kg on Monday. Despite the increase in moisture, instability, and mixing ratios models show an increase in CIN (100-200 J/kg). Activity each day will depend on how the day prior plays out. But right now, Monday looks to have slightly better chances than Sunday. Either way, most of the lower deserts are expected to remain dry with the best chances (and coverage) of thunderstorms expected across the higher terrain areas to the east of the Phoenix Metro. && .LONG TERM /TUESDAY THROUGH NEXT FRIDAY/... Ensemble members are in good agreement that by Tuesday drier air will start to filter back into the region as the subtropical high starts to retrograde back over our region. By the middle of the week the center of the high will be straddling the AZ/NM border and by the end of the week the center of the high will be over AZ. As the high moves overhead, PWATs will drop into a 0.8-1.2" range across our region and steering flow will be out of the S/SW. The combination of these factors will lead to poor chances for thunderstorm development across the region. The NBM shows that Tuesday and Wednesday there could be enough moisture around to support isolated thunderstorm chances for the higher terrain areas. But by the end of next week thunderstorm chances for our area shut off and will mainly be relegated to the Mogollon Rim. Unusually hot temperatures will be the main story next week. As mentioned above the subtropical high will slowly retrograde back over our region beginning on Tuesday, which will result in a gradual warming trend for our area. The high is also expected to strengthen to around 596-598dam during this time. The combination of the center settling over our region and strengthening will result in temperatures heating up to around 10 degrees above normal for this time of year. Afternoon highs (morning lows) are forecasted to be in the 110-116 (85-95) degree range across the lower deserts and in the 100-110 (75-85) degree range across the higher terrain areas. The increase in temperatures will also result in an increase in HeatRisk, with widespread Extreme HeatRisk forecast for the majority of the CWA by Wednesday. There remains high confidence in the heat forecast for next week. So, the Extreme Heat Warning remains in effect through next Friday and will likely need to be expanded to more areas by the middle of the week and may eventually need to be extended into next weekend. && .AVIATION...Updated at 0515Z. South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation concerns are expected through early Saturday afternoon under SCT to sometimes BKN cloud decks. Winds will follow familiar diurnal trends with periods of VRB conditions during the overnight hours. Forecast confidence decreases for late Saturday afternoon into the evening timeframe. There is a signal that VCSH/VCTS will initiate as early as 23Z, though rain chances are only around 20% at this time. To reflect convective uncertainty, PROB30 groups have been added to each metro terminal. If storms do develop, they could provide multiple outflows, resulting in gusty and erratic winds, and depending on where the outflow originate, BLDU could also become a operational factor. Changes in subsequent TAF updates should be anticipated. Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation concerns are expected through the front half of the TAF period. Winds will favor a westerly component at KIPL, while VRB conditions will be common at KBLH through Saturday morning. Forecast confidence decreases as we transition into the afternoon timeframe due to uncertainty of convective activity. VCTS have been hinted at for KIPL, but rain chances currently stand at <10%. This TS signal has been consistent for the past several hours, so as to not completely ignore the potential, a PROB30 group has been added to the TAF. Gusty westerly/southwesterly winds and brief reductions in VIS will be the main concerns with any storms that come to fruition. Convection looks as if it will remain outside the vicinity of KBLH, but any changes in forecast guidance may yield the addition of a PROB30 or VCTS into that TAF as well. && .FIRE WEATHER... Hot and seasonally dry conditions are expected nearly every day, through next week. Aside from a brief increase in moisture Sunday- Monday, minimum RH values each afternoon will be around 12-18% (15-25% Sun-Mon). Temperatures will be around 5-10 degrees above normal through the next week, with lower desert highs eclipsing 110 degrees most afternoons. There will be slight chances for storms each afternoon through Monday, but they will mostly favor the higher terrain areas. Drier conditions, with lower storm chances are expected by the middle of next week. Outside of thunderstorm outflow winds, winds will follow the typical diurnal tendencies with some modest afternoon upslope gustiness. && .CLIMATE... Record highs: Date Phoenix Yuma El Centro ---- ------- ---- --------- Aug 21 114 in 2019 115 in 1969 117 in 1969 Aug 22 113 in 2011 115 in 1969 117 in 1969 Aug 23 114 in 2011 115 in 2011 116 in 1969 Aug 24 115 in 2020 119 in 1985 117 in 1985 Aug 25 113 in 2011 116 in 1962 117 in 1962 Aug 26 117 in 2011 115 in 2020 115 in 1981 Aug 27 114 in 2023 120 in 1981 117 in 1981 Aug 28 117 in 2023 118 in 2023 117 in 2009 && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Extreme Heat Warning until 8 PM MST Friday for AZZ530>555-559- 560. CA...Extreme Heat Warning until 8 PM PDT Friday for CAZ562-565>567- 569-570. && $$ SHORT TERM...Berislavich LONG TERM...Berislavich AVIATION...RW FIRE WEATHER...Berislavich/Benedict CLIMATE...18