037 FXUS65 KPSR 301750 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 1050 AM MST Tue Dec 30 2025 .UPDATE...Updated Aviation Discussion. && .KEY MESSAGES... - High pressure will stick around for one more day, keeping the dry conditions and above normal temperatures in place. - An unsettled weather regime will lead to periods of light rain from Wednesday afternoon through Thursday night. - Drier weather should return by the weekend with temperatures still hovering near to slightly above normal. && .SHORT TERM /Today through Wednesday/... Upper level ridging is now fully in control across the region, but it won't last long as a large cut-off low to our southwest will start to move toward the area later today into Wednesday. Ahead of this low, we are already seeing strong moisture advection above 20K feet with guidance showing this moisture to gradually lower to between 12-15K feet later today. The ridge overhead has pushed H5 heights to around 580-582dm leading to noticeable warming. The higher clouds today may keep daytime highs down slightly, but NBM guidance still shows readings from the lower 70s across the western lower deserts to the mid 70s in the Phoenix area. Moisture will continue to improve over the region on Wednesday as the large cut-off begins to move in from the southwest. Forecast PWATs are shown to increase to around 250% of normal by Wednesday morning before peaking around 300% of normal Wednesday afternoon through Wednesday night. Forced ascent will begin to increase during the daytime hours Wednesday with models showing a band of light rain developing along a leading wing of vorticity. There is still some uncertainty how much rain will fall with this first band of rain as there will still be some residual dry air in the lower levels. However, recent guidance has been trending toward a faster top-down saturation and this may lead to much of the area seeing a few hours of steady light rainfall with measurable amounts potentially as high as 0.10-0.20" during the latter half of Wednesday. && .LONG TERM /Thursday through Monday/... After the first batch of rain moves through the area later on Wednesday, there looks to be a break in the organized forcing Wednesday night into Thursday morning. However, there should still be enough upslope ascent for some scattered showers focused just to the north and northeast of the Phoenix area. The next round of more organized rain is likely to come from the main shortwave trough as it finally tracks across southern California Thursday morning into central Arizona Thursday afternoon and evening. This should bring another decent batch of showers, first over southeast California Thursday morning and then through southern and central Arizona Thursday afternoon. This additional rainfall should bring the storm total rainfall up to an average of 0.05-0.15" across the western deserts, 0.10-0.25" across the south-central Arizona lower deserts and 0.25-0.50" over the higher terrain northeast of Phoenix. Rain chances will gradually diminish Thursday evening into Thursday night with any lingering chances mainly focused over the Arizona higher terrain after midnight. Upper level ridging and drier air aloft will quickly work into the region by Friday, ending rain chances across the higher terrain by around noon Friday. Gradual drying is expected to continue through the weekend as troughing remains positioned across the eastern Pacific into the Western U.S. There will likely be another couple of shortwaves moving through the trough through early next week, but the first one should miss our region to the north. By the time the second one potentially gets close to our region early next week, moisture should be much more limited resulting in little if any additional rain chances. Despite the unsettled weather pattern late this week into next week, temperatures are expected to stay quite mild. The NBM shows daily highs mostly in the upper 60s to the lower 70s with overnight lows staying at least 10 degrees above normal through Friday night. Eventually by early next week, overnight lows will dip lower with readings back into the 40s to lower 50s once some drier air moves back into the area. && .AVIATION...Updated at 1750Z. South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation concerns will exist through Wednesday morning under SCT-BKN mid and high cloud decks. Winds will maintain an east component through the period, with speeds currently 10-15 kts (and occasional higher gusts) at KPHX and 5-10 kts at the other terminals. Speeds will gradually decrease heading through the afternoon into the evening. Wednesday by mid-late afternoon, anticipate SHRA and lower CIGs to enter the airspace from the southwest. This shower activity will likely cause an abrupt, temporary wind shift out of the southwest as it approaches the terminals. CIGs should prevail around 050-070 by 00Z Thursday but are anticipated to continue lowering through the evening hours. Low to moderate confidence in MVFR CIGs exists Wednesday night into Thursday morning (up to 40-50% chance). Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation concerns are expected through Wednesday morning under SCT-BKN mid and high cloud decks. Winds will generally vary between north and west with speeds AOB 10 kts, becoming very light with periods of variability overnight. By the end of the TAF period, lower decks of clouds (070-100 at 18Z Wednesday) will begin to fill in over the airspace and continue to lower heading into the afternoon. A period with VCSH conditions may develop at both terminals by the afternoon. && .FIRE WEATHER... Slightly above normal temperatures and dry conditions will give way to a rapid increase in moisture Wednesday. Minimum humidity levels in a 20-30% range at lower elevations, and somewhat higher in far eastern districts today will increase closer to 25-40% Wednesday before peaking at 50-70% for Thursday and Friday. Enhanced north to northeast winds will be common again today, particularly across ridge tops of eastern districts where gusts of 20-30 mph will be possible through early afternoon. Speeds should relax by Wednesday as clouds and humidity levels increase. Periods of showers are then expected during the latter half of Wednesday through Thursday with overall light rainfall amounts for much of the lower deserts to 0.25-0.75" in higher terrain areas. Somewhat drier conditions will work back into the region by the weekend, but humidities will remain elevated as temperatures remain 5-8 degrees above normal. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ SHORT TERM...Kuhlman LONG TERM...Kuhlman AVIATION...Whittock FIRE WEATHER...Kuhlman