774 FXUS65 KPSR 101113 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 413 AM MST Tue Jun 10 2025 .UPDATE...Updated 12Z Aviation Discussion. && .KEY MESSAGES... - Dry conditions through the period with above normal temperatures through the week, peaking upwards of 7-10 degrees over the weekend - Fairly widespread Moderate HeatRisk through the entire week with increasing Major HeatRisk starting by Sunday && .DISCUSSION... Early morning IR satellite depicts clear skies across the region, while a slug of enhanced moisture levels in northern Arizona, evident in WV imagery, is creeping southward into the northern portions of south-central Arizona. These enhanced moisture levels aided in some shower and thunderstorm across the higher country of northern Arizona yesterday by a weak troughing feature that continues to deepen across the state today. This trough will aid in more robust convective activity into New Mexico today, with some high country showers and thunderstorms north of the region. Conditions are too dry and stable across the immediate region to warrant any chances of shower/storm potential today. This troughing feature continues to cap lower desert high temperatures in the mid to upper 100s through the middle of this week, with continued westerly to northwesterly flow keeping high temperatures in this general range through the rest of the week under fairly widespread Moderate HeatRisk. Late in the week, a closed low in the Gulf of Alaska will begin to amplify and deepen across the Pacific Northwest, resulting in the subtropical ridge currently centered offshore from the Baja Peninsula to build into the Desert Southwest going into this weekend. This change in the pattern will result in another warming period across the region, as probabilities of temperatures exceeding 110 degrees across the lower deserts are becoming much more likely over the weekend and even into early next week depending on the lower desert location (60-100% chance). The increasing alignment amongst the ensemble members are resulting in continued warming NBM deterministic temperature outputs for the lower deserts, with increasing Major HeatRisk coverage, particularly on Sunday and Monday, as high soar into at least the lower 110s. Thus, there is increasing concern about the first impactful heat event of the season that will likely result in the first Extreme Heat products of the year should these trends hold, so stay tuned. The evolution of the aforementioned troughing feature in the Pacific Northwest will dictate the length of this heat event, as ensembles begin to diverge by a decent amount starting on Monday as to how much this trough will dislodge the subtropical the ridging in place through the middle of next week. So, while temperatures would cool under this pattern transition, how quickly and the magnitude of cooling is much more uncertain at this time, as evidenced by the six degree IQR spread in NBM high temperatures for Phoenix by next Tuesday. && .AVIATION...Updated at 1113Z. South Central Arizona including KPHX, KIWA, KSDL, KDVT; and Southeast California/Southwest Arizona including KIPL and KBLH: No major weather issues will exist through Tuesday evening under mostly clear skies. Winds will continue to follow their typical diurnal tendencies, with periods of light and variable to calm winds especially during diurnal transitions. Periodic afternoon/early evening gusts 15-20kt (slightly stronger, 20-25 kts, at KBLH) will continue today with minimal operational impacts. && .FIRE WEATHER... Dry conditions will continue through the week with above normal temperatures. Min RHs will be around 10-15% through much of the week, while Max RHs range between 20-50% (poorest in the eastern districts). Winds will tend to follow their typical diurnal tendencies with periods of modest afternoon upslope gustiness. Temperatures are forecast to further heat up this upcoming weekend with afternoon highs in excess of 110 degrees likely by Sunday across the lower deserts as Min RHs lower in the 5-10% range. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Young AVIATION...Berislavich/Whittock FIRE WEATHER...Young/Smith