FXUS65 KPSR 092126 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 226 PM MST Fri May 9 2025 && .SYNOPSIS... High pressure is strengthening over the region leading to temperatures in the triple digits today lasting through the weekend, up to 105 degrees on Sunday. This has lead to widespread Moderate HeatRisk and some localized Major HeatRisk in the western portions of the region. Skies will remain clear through Saturday, afterwards higher level cloud coverage will be common. Breezy conditions will also start Saturday, calming down slightly on Sunday before ramping back up Monday as a low pressure system approaches. This system will also help bring temperatures down. && .DISCUSSION... Upper level ridging has become dominate over the region as temperatures are expected to climb just over 100 degrees today and continue to rise over the weekend as the ridge continues to build. Peak H5 heights look to be between 585-587dm, just into the 90th percentile of climatology for this time of year. This will very likely (>90%) put high temperatures between 104-106 over the weekend. These temperatures have elevated the HeatRisk to Moderate widespread across a the desert SW, with Major HeatRisk in very localized areas in the western portions of the region starting Saturday. While most of the region is anticipated to be back under Minor HeatRisk the Phoenix Metro holds onto Moderate risk into Monday before dipping back down to Minor. Clear skies through Saturday, with higher level cloud coverage starting Sunday, which may lower the max temperature output by the NBM. Winds are forecast to pick up Saturday morning from the east/south-east across much of southern and central Arizona, with gust speeds around 25-35 mph. This is mainly due to an increasing gradient between our high pressure ridge and a strengthening low over the Lower MS River Valley. Winds will relax by the afternoon hours and will see a similar trend Sunday. Models show the relatively deep trough off the Pacific NW affecting H5 heights in the region by Sunday. However, temperatures are very unlikely (<10%) to be affected on Sunday. This system looks to weaken as it pushes further inland, but will still impact the region once its situated over the Great Basin by Monday. During which area wide breezy conditions will pick back up. Ensembles still agree this Pacific trough will be fairly slow to fully move through the region, not until next Tuesday or Wednesday. There is still some uncertainty with the exact timing and the depth of the system, with NBM temperatures slowing the cool down early next week, but we could see highs eventually drop into the 80s by Wednesday. && .AVIATION...Updated at 1735Z. South Central Arizona including KPHX, KIWA, KSDL, KDVT: Winds at all terminals will predominately exhibit an easterly component through the TAF period. A period of light and variable winds is expected this evening. Skies will remain mostly clear with low probabilities of FEW clouds moving into the are this evening. Look for gusty E-ESE winds around the 15Z timeframe tomorrow morning aob 15-25 knots. Southeast California/Southwest Arizona including KIPL and KBLH: Wind speeds at both terminals will generally be light and variable through the TAF period. Expect winds at KBLH to have an easterly component shifting northerly by 05Z tonight. Skies will remain mostly clear. && .FIRE WEATHER... High pressure will strengthen over the region into the weekend leading to hot temperatures and highs topping 100 degrees over the majority of the lower deserts through Sunday. Humidities will drop a bit further today with MinRHs around 15% before dropping closer to 10% by Sunday. After light winds today, winds will become quite breezy out of the east on Saturday with peak gusts of 25-35 mph during the morning hours across portions of southern Arizona. Expect another round of easterly breezy conditions Sunday morning across eastern Arizona before breezy conditions expand to include the western districts Sunday afternoon. These conditions may lead to a period of elevated fire danger in some areas this weekend. An approaching low pressure system early next week will lead to a cooling trend, but also more breezy to windy conditions which will likely bring a continuation of the elevated fire danger. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Kuhlman/Ryan AVIATION...95/Berislavich FIRE WEATHER...Kuhlman/Ryan