597 FXUS65 KPSR 141110 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 410 AM MST Mon Apr 14 2025 .UPDATE... Updated Aviation && .SYNOPSIS... Well above normal temperatures will continue through the early portions of this week. Cooler temperatures to potentially below normal levels expected to develop late this week and into the weekend, as a weather disturbance may also bring in some low end precipitation chances to the region Friday into Saturday. && .DISCUSSION... A good stream of mid to upper level moisture from the southwest continues to persist across the region this morning, resulting in mostly cloudy to cloudy skies. This is due to a persistent upper level low that remains in the eastern Pacific offshore of the Baja Peninsula, where the southeastern flank is tapping into sub-tropical moisture. This mornings cloudiness is keeping overnight temperature elevated to the point where the warm low temperature on record for this date may be challenged (71 and 69 degrees for Phoenix and Yuma). Otherwise, despite broken to overcast skies throughout the day, NBM deterministic is still pegging lower deserts to reach into the lower to mid-90s this afternoon. Hi-res models show some breaks in the clouds late this morning and into the afternoon hours, so we`ll see if that`ll come to fruition and result in these temperatures, which area still running well above normal. Very dry conditions will persist, with thicker mid-level decks resulting in some virga and some sprinkles across mainly western to central Arizona through tomorrow before clearing out going into Thursday. As the aforementioned upper level trough encroaches on the Desert Southwest going into the middle of the week, temperatures will gradually cool. However, general cloudiness may result in overnight temperatures remaining near record high levels through at least tomorrow morning. Much more pronounced cooling is set to occur on Thursday, as the pattern becomes more negatively anomalous in the mid-levels across the region, as the upper level low phases with a Pacific Northwest trough to a certain extent heading into the latter portions of the week. This phasing of the troughs still has quite a bit of uncertainty in terms of how much of the Pacific Northwest trough will get absorbed into the Desert Southwest, but there is a considerable shift towards this becoming the expectation given the latest ensemble cluster analysis (60-70% chance of this scenario). Even with this increased confidence in the deeper solution, spread is still considerable in terms of how amplified this trough will become, which will affect how quickly and to what magnitude cooling will occur across the region through the end of the week and into the weekend. NBM interquartile ranges are still quite large for Thursday-Saturday, where the coolest solutions would result in highs in the middle 70s, while a lesser impact from the Pacific trough would keep temperatures in the lower to mid-80s. Additionally, precipitation chances will be highly dependent on the more amplified pattern bringing in more robust moisture into the region. Clusters are showing a large difference for any precipitation timing into Arizona as early as Friday, with a more amplified, slower solution delaying precipitation until Saturday. Even the most robust solutions look to be limiting precipitation mostly to higher terrain areas, as the latest NBM PoP`s Friday into Saturday are hovering no higher than 20% for lower desert areas. How quickly this trough moves eastward across the region will then impact how quickly temperatures will respond late this weekend and into next week. && .AVIATION...Updated at 1110Z. South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Only minor weather issues will exist through Tuesday morning under frequent periods of thick mid/high cloud decks. Confidence is good that an easterly wind component will prevail through at least early afternoon before slowly transitioning to a westerly direction. Confidence is much lower with respect to timing of this wind shift, and a prolonged period of 140v220 may be common mid afternoon before completing the switch very late afternoon. Virga should be fairly widespread during the evening which could conceivably create briefly erratic directions. Thereafter, the preponderance of model output suggests west winds holding much later than usual into the evening/overnight before reverting back to an easterly component. Southeast California/Southwest Arizona including KIPL and KBLH: No major weather issues will exist through Tuesday morning under periods of thick mid/high cigs. Light and variable winds will be common during late night/early morning hours with directions trending towards S/SE during the afternoon and evening. A few stronger gusts 15-20kt may be possible, especially at KBLH however expansive cloud cover may hinder more persistent and widespread gustiness. && .FIRE WEATHER... Areas of elevated fire weather conditions continue through early this week, mostly due to the very low RH`s, where minimum RH`s will remain below 15% through tomorrow. More impactful fire weather conditions is expected to redevelop during the middle portions of the week, as very dry conditions linger through Wednesday, with wind starting to increase (15-25 mph sustained), specifically across the higher terrain areas of the eastern districts. Elevated to locally critical fire weather conditions are expected to last Wednesday and Thursday, particularly for the eastern districts as winds remain elevated. Improving RH`s and weakening winds should relieve fire weather concerns going into this weekend. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Young AVIATION...18 FIRE WEATHER...Young