


Area Forecast Discussion
Issued by NWS Phoenix, AZ
Issued by NWS Phoenix, AZ
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153 FXUS65 KPSR 172306 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 406 PM MST Fri Oct 17 2025 .UPDATE...Updated 00Z Aviation Discussion. && .KEY MESSAGES... - Dry and tranquil weather conditions with zero rain chances will prevail through the weekend with temperatures gradually warming into the normal range. - Temperatures will warm a bit further early next week with lower desert highs topping out around 90 degrees before cooling back into the normal range later in the week. - A passing weather system during the middle of next week may bring some light shower activity focused over the Arizona high terrain. && .SHORT TERM /TODAY THROUGH SATURDAY NIGHT/... Current mid-level water vapor imagery depicts broad troughing over the northern Rockies and Northern Plains, with a positively tilted, elongated shortwave progressing through AZ. Upstream, a few features also evident in water vapor imagery will begin to influence the region during the forecast period: 1) upstream ridging over the northeast Pacific and 2) an upper low, detached from the northern stream and meandering off the Southern CA/Baja Coast. For today, continued negative midlevel height anomalies aloft (thanks to the shortwave progressing through the region) will support below normal temperatures once again, with afternoon highs in the lower to middle 80s across the typically warmer lower desert locales. Additionally, enough moisture is present ahead of the shortwave that fair weather cumulus have developed over the AZ high terrain and Southeast AZ, which will linger through the rest of the afternoon. The shortwave overhead will quickly eject eastward tonight, allowing midlevel heights to quickly build into the region from the southeast. This process will be aided somewhat by the progressive northern stream, as the northeast Pacific ridge shifts over the northwest US. The cutoff low off the SoCal/Baja Coast may also act to "pump" up midlevel heights downstream as it meanders closer to the Coast tomorrow. Regardless, ensembles agree that H5 heights will reach a 587-589 dam range by Saturday night, supporting a warming trend to near normal temperatures over weekend. Expect afternoon highs to warm solidly into the middle 80s across the lower deserts tomorrow afternoon, just a few degrees shy of daily averages. && .LONG TERM /SUNDAY THROUGH THURSDAY/... The latest model guidance has shifted slightly toward higher heights for Sunday through at least Tuesday as the developing cut- off low is now shown to be a bit farther to the west off the coast of Baja. These likely higher heights have bumped up the temperature forecast for Sunday- Tuesday by two or three degrees with the NBM now showing highs closer to or even reaching 90 degrees during the period. These forecast highs are still basically within the normal range for this time of year. The dry boundary layer conditions and clear to mostly clear skies will continue to promote efficient nocturnal cooling with overnight lows only rising into the upper 50s to mid 60s by early next week. Modest forecast uncertainty remains for the eventual conclusion of the cut-off low, but at least the GEFS and EPS are in better agreement than last night. Both models show the cut-off low beginning to weaken as it starts to make northeastward progress toward southern California on Tuesday. They also show a very similar track of bringing the low into southern California around Tuesday night, but the GEFS weakens the system more quickly showing an open wave before moving onshore. Both model suites also agree on some modest southerly moisture advection into south- central and southeastern Arizona at some point later Tuesday/early Wednesday, but mean PWATs are only shown to reach 0.6-0.8" or on the higher end of the climatological normals. Assuming no major changes to the forecast of this cut-off low, any fairly limited rain chances are likely to be focused over higher terrain areas of south-central and eastern Arizona late Tuesday into early Wednesday. Temperatures should also retreat some as the system passes through our region with NBM highs falling more into the mid 80s by next Wednesday. Looking out a bit further, we should stay in a dry westerly somewhat zonal flow going into next weekend. A Pacific trough is forecast to move onshore somewhere across the Pacific Northwest/California by next weekend, but for now guidance favors this system mostly bypassing our region to the north. && .AVIATION...Updated at 2305Z. South Central Arizona including KPHX, KIWA, KSDL, and KDVT; and Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather concerns are anticipated through the TAF period. Winds across the Phoenix area terminals will follow diurnal tendencies with extended periods of light and variable to at times calm conditions. Winds at KIPL will predominantly favor a northerly component, with extended periods of variability, while directions at KBLH vary between NNE and NW. Expect light winds aob 7 kts through the period under mostly clear skies. && .FIRE WEATHER... Dry, tranquil weather with temperatures gradually warming into the normal range will prevail through the weekend. Minimum afternoon humidity levels will fall into a 15-25% range across the lower deserts to upwards of 30-35% over the eastern Arizona high terrain today before falling more into a 15-25% range areawide starting Saturday. Overnight recovery will remain good to excellent. Light diurnal winds are expected across the eastern districts, while some occasional breezy northerly winds will be seen across the western districts today. Near to slightly above normal temperatures with MinRHs between 15-25% are forecast to continue through early next week. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ SHORT TERM...Whittock LONG TERM...Kuhlman AVIATION...Berislavich/Smith FIRE WEATHER...Kuhlman