256 FXUS65 KPSR 090536 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 1036 PM MST Sun Jun 8 2025 .UPDATE...Updated 06z Aviation Discussion. && .DISCUSSION... KEY MESSAGES: - Dry conditions through the period with temperatures peaking upwards of 10 degrees above normal early this week - Widespread moderate HeatRisk through the first half of this week relaxing slightly by the end of the week Very little has changed recently in the western hemisphere synoptic pattern with Rex blocking dominating the western Conus and deep negative height anomalies spinning into the Upper Midwest/Great Lakes. Strong subtropical ridging continues to hover south of the international border, but will remain dampened as a result of the zonal, basal jet streak comprising the blocking structure limiting any poleward expansion. As such, H5 heights will hover in a 586- 590dm range the next several days with the thermal response maximized over the next 48 hours. Numerical guidance spread remains relatively narrow advertising temperatures some 5F-10F above normal through at least the middle of the week before the Conus flow pattern modifies. NBM output continues to show lower elevations of SE California with the best odds (70-90%) of hitting 110F with probabilities decreasing to a 50-70% range across the SW Arizona, and generally less than 50% in the Phoenix Metro. Regardless, widespread moderate HeatRisk will exist across the lower desert communities through midweek. Ensemble members remain consistent in depicting a breakdown in hemispheric blocking during the latter half of the week due to progressive Pacific jet energy introducing a series of shortwaves into the NW Conus. However, trends in ensemble membership continue to advertise less aggressive midlevel height falls into the western Conus keeping the primary negative height anomalies well offshore. As a result, height falls across the SW Conus will be extremely subtle and forecast models are now advertising almost no reduction in temperatures into the end of the week. Instead, a growing preponderance of ensemble members suggest subtropical ridging finally building into the forecast area ahead of the East Pacific troughing with H5 heights in excess of 590dm spreading north and west. In fact, almost all GEFS members depict a 595dm anti-cyclone settling near the AZ-NM border by the end of the weekend with an increasing percentage of CMC membership quickly following suit. Thus, its becoming more likely widespread lower elevations 110F+ readings will materialize by the end of this forecast period with growing odds of notable major HeatRisk and extreme heat headlines. && .AVIATION...Updated at 0535Z. South Central Arizona including KPHX, KIWA, KSDL, KDVT: No aviation weather concerns are expected through the TAF period under clear skies. Winds will continue to follow diurnal patterns, with period of variability during the forecast direction switches. Westerly winds will be slightly stronger tomorrow afternoon and are expected to persist later in the evening, with gusts to 15-20 kts likely to prevail for several hours during the late afternoon. Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation concerns will exist through Monday evening under clear skies. West winds at KIPL and southwest winds at KBLH will subside over the next few hours, followed by an extended period of light and VRB winds for much of Monday morning. Monday afternoon, SE-S winds at KIPL are expected to veer out of the SW and are likely (60% chance) to gust to around 20-24 kts for a few hours, and at KBLH, S-SW winds will pick up and prevail through the end of the period with gusts to around 20 kts during the late afternoon. && .FIRE WEATHER... Temperature will remain above normal through the week with the warmest readings occurring the next couple days. MinRHs will fall into the single digits Monday, then just above 10% the remainder of the week. Poor to fair overnight recovery of 20-40% will be common. Winds will tend to follow their typical diurnal tendencies with periods of afternoon upslope gustiness. Some enhanced gustiness may affect some districts during the end of the week resulting in a slightly elevated fire danger. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...18/Berislavich AVIATION...Whittock FIRE WEATHER...18/Berislavich