170 FXUS65 KTWC 302038 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 138 PM MST Tue Dec 30 2025 .SYNOPSIS...Gusty east to southeast winds for portions of southeast Arizona will diminish by Wednesday morning. A Pacific storm system will impact our area from Wednesday afternoon through New Years Day and lingering into Friday morning with multiple rounds of shower activity through the period. Dry conditions return Friday afternoon through the weekend. Above normal high temperatures continue for most of the upcoming week. && .DISCUSSION...The mid/upper level pattern consists of an upper level low over the eastern Pacific near 30N/128W with a ridge axis downstream across the eastern half of Arizona. While ridging aloft is still in control of our weather with above normal heights/thicknesses resulting in warm daytime temperatures, the area will become under the influence of the Pacific weather system Wednesday into Friday. We're already seeing the beginning influences this afternoon with thick cirroform/high level clouds spreading in. Meanwhile, in the near term, we're still dealing with some gusty east winds (especially in susceptible areas near and downwind of mountain gaps). KTUS had a gust to 53 MPH this morning. These east winds will gradually decrease this afternoon but still persist in the 10 to 20 mph range into Wednesday morning in those prone east wind areas. Mainly light winds under 10 mph elsewhere. Into the day Wednesday, the aforementioned mid/upper low will remain nearly stationary, just starting to eject eastward in the afternoon. Our area will become more under the influence of south to southwest flow aloft as a disturbance on the southeast periphery of the Pacific storm system moves into and through the region Wednesday afternoon into Wednesday night/New Years eve. As this occurs, the atmosphere will be moistening up from the top-down with enough lift to produce light shower activity. These showers will overspread the region from southwest to northeast as early as the late morning (south and west of Tucson) to the remainder of southeast Arizona as the afternoon progresses. For those that have New Years Eve plans outdoors, be sure to take an umbrella as scattered showers will continue during the evening across southeast Arizona. Rain amounts through early Thursday morning will be light, ranging from 0.05" to 0.20" for most locales with up to 0.25" to 0.50" for the mountains. Snow levels will remain above mountain tops during this time. For much of Thursday morning, the area will see a break with reduced shower activity before the upper low ejects eastward Thursday afternoon into Thursday night. As it does so, the low will transition more into an open wave sliding across central and northern Arizona Thursday night into Friday morning. The latest trends for Thursday afternoon into Friday morning is for the most widespread shower activity to be from Tucson and points north and westward (closer to the deeper lift/forcing from the trough) with less coverage/lower chances south and east. With increased instability on Thursday afternoon and a more convective nature in the precipitation, wouldn't be surprised if there was some thunder embedded within the heavier precipitation. Also, given the more convective precipitation, the precipitation amounts will tend to be more variable Thursday afternoon into Friday morning. Most likely additional precipitation amounts Thursday PM to Friday AM will range from 0.01" to 0.20" with locally 0.25" to 0.50" north of Tucson and in the mountains. Therefore, the most likely total event precipitation from Wednesday into Friday will range from about 0.10" to 0.50" (lowest SE Cochise County and highest north of Tucson), with 0.50" to 1.00" in the mountains (Catalinas/Rincons northeastward) due to orographic lift. As shortwave ridging builds in Friday, any lingering precipitation north and east of Tucson will taper off during the morning with dry conditions returning pretty much everywhere by Friday afternoon. Our area will still be under the influence of the ridge Saturday as the axis shifts east into New Mexico by Saturday afternoon. Following that, expect a return to southwest flow aloft Sunday through Tuesday ahead another Pacific trough. Current forecast is dry Sunday and Monday but these patterns sometimes have sneaky disturbances embedded within the flow that are not well modeled so we'll have to monitor for that and potential precipitation chances. Timing differences become more apparent by Tuesday and beyond with the next trough but all indications are we'll have another system in our future around the middle of next week. This one will be more typical for what we see around here with snow levels low enough to bring snow chances into the mountains. Temperatures will remain about 5 to 8 degrees for most of the upcoming period. && .AVIATION...Valid through 01/00Z. BKN-OVC clouds AOA 15-20k ft AGL through 31/12Z, then becoming BKN- OVC with cloud bases lowering to 6-12k ft AGL through the end of the valid period. SCT -SHRA expected to develop and spread from southwest to northeast, with increasing -SHRA chances for KTUS/KOLS aft 31/19Z and KDUG aft 31/23Z. SFC winds ELY/SELY 10-20 kts with gusts to 25-35 kts thru 31/01Z, then diminishing to 5-10 kts gusting 15-20 kts thru 31/18Z. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Gusty east winds into Wednesday morning with the strongest gusts in excess of 30 mph diminishing by early this evening. Otherwise, winds mainly less than 15 mph from Wednesday afternoon into early next week. A weather system will bring periods of rain showers from Wednesday afternoon into Friday morning. Any snow will be at or above mountain tops. Minimum relative humidity values will remain elevated through the upcoming week, ranging from 35-45 percent in the valleys and 50-70 percent in the mountains. Temperatures will mostly be above normal levels this week. && && .TWC WATCHES/WARNINGS/ADVISORIES... None. && $$ Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson