737 FXUS65 KPSR 112328 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 428 PM MST Wed Jun 11 2025 .UPDATE...Updated 00Z Aviation Discussion. && .KEY MESSAGES... - Dry conditions with temperatures remaining 3 to 5 degrees above average across the region through Friday. - A strong ridge of high pressure will build over the Desert Southwest this weekend, promoting the hottest temperatures of the year thus far. - An Extreme Heat Watch is in effect from Saturday morning through Monday evening for high temperatures ranging from 106 to 115 degrees across the lower deserts. && .DISCUSSION... Extreme heat will become the main weather concern by this weekend as temperatures reach their highest levels of the year so far. Today we will continue to see temperatures right around 3 to 5 degrees above average across the region as a broad upper lvl ridge sits off the coast of the Baja California. Our forecast area will remain under the influence of this ridge over the next few days as it continues to slowly migrate ewd. As this shift in the ridge occurs, 500 mb heights will range from 588-592 dam or near the 90th percentile of climatology, resulting in high temperatures remaining steady around 104-108 degrees through Friday. Heading into this weekend, ensembles (GEFS and EPS) are still in excellent agreement that the afomentioned upper lvl ridge will continue to build and strengthen over the Desert Southwest and reposition over the AZ/NM border by Saturday. Over the weekend, 500 mb heights within the center of the ridge are projected to reach 595- 595 dam with 592-594 dam heights overspreading our entire forecast area. These heights are around the 95th percentile of climatology for mid June. Along with the increasing heights/thicknesses, 850 mb temperatures will rise to around 27-30C on Saturday and 28-32C on Sunday and Monday which would equate to surface temperatures of 108- 111F on Saturday and 110-115F on Sunday and Monday across the lower deserts. The chances for tying the record high of 115F at Sky Harbor is now 30% on Sunday and 20% on Monday. Temperatures of this magnitude will result in areas of Major HeatRisk with the most widespread Major HeatRisk occurring on Sunday. Make sure to follow heat safety guidance this weekend by limiting time spent outdoors to the early morning or evening hours and staying hydrated. There is still a high degree of uncertainty regarding the arrival of a shortwave trough on Tuesday which could potentially result in cooler temperatures across the region. The magnitude of cooling will greatly depend on the depth and positioning of this trough as some model members are depicting a weaker and faster solution (EPS) and others (GEFS) are suggesting slower and deeper trough which would foster cooler temperatures. Right now NBM highs on Tuesday are ranging from 104-108 degrees which would indicate a break in the extreme heat conditions at least through the middle of next week. The trough on Tuesday could bring an uptick in winds, especially to the higher terrain areas of southcentral AZ where gusts could reach 20-30 mph, however our forecast area looks to remain dry. && .AVIATION...Updated at 2328Z. South Central Arizona including KPHX, KIWA, KSDL, KDVT; Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation weather concerns are expected through the TAF period. Winds continue to exhibit diurnal tendencies and will continue to gust for the next few hours but look to relax late this evening into the overnight hours. Out west at KBLH gusty conditions will return with speeds generally between 20-25kts but could see period near 30kts. FEW high clouds will persist at all terminals. && .FIRE WEATHER... Above normal temperatures and dry conditions will prevail through the remainder of this week. Winds will continue to follow typical diurnal tendencies with periods of modest afternoon upslope breeziness (gusts of 20-25 mph at times). Minimum humidity will bottom out between 10-15% over the next few days with poor to fair overnight recovery between 20-50% region-wide. Temperatures are forecast to spike well above normal this upcoming weekend with afternoon highs reaching 110 or hotter as early as Saturday across the lower deserts as Min RHs lower in the 5-10% range. By early next week, the arrival of a dry weather system may result in an uptick in winds across southeast CA and the higher terrain areas of southcentral AZ. These gusty winds combined with dry fuels and very low humidity could result in elevated fire weather concerns. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Extreme Heat Watch from Saturday morning through Monday evening for AZZ530>544-546>556-559>562. CA...Extreme Heat Watch from Saturday morning through Monday evening for CAZ562>567-569-570. && $$ DISCUSSION...Salerno AVIATION...Ryan FIRE WEATHER...Salerno/Kuhlman