Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
707 FXUS65 KTWC 120951 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 251 AM MST Wed Nov 12 2025 .SYNOPSIS... High temperatures will remain 5 to 10 degrees above normal through Friday. A low pressure system is then expected to impact the region this weekend, bringing chances for rain and high elevation mountain snow, much cooler temperatures, and breezy conditions. Unsettled conditions are expected to continue early next week along with below normal temperatures. && .DISCUSSION... A digging trough over the eastern Pacific will close and slowly approach the west coast over the next 48 hours, while downstream a ridge axis currently over the desert southwest will shift east and give way to southwest flow aloft. While this trough remains upstream of southeastern Arizona, temperatures will remain above normal and an increasing stream of high level cirrus will spread over the region. The aforementioned trough, likely becoming a closed low off the California coast by Friday, poses a hefty forecast challenge. Models typically struggle with closed lows, often making them too progressive and quick to move downstream. With that in mind it`s no surprise this low is causing model run to run inconsistencies in its arrival and strength. Model runs over the last 24-36 hours have been slower to bring the low into southeastern Arizona, with precipitation chances in this forecast package now held off until at least early Saturday for western to central portions of Arizona. Even that may be too fast as some 00Z deterministic models now delay QPF in southeastern Arizona until early Sunday. There remain ensemble members and recent model runs that do bring the upper low in quicker on Saturday but it wouldn`t be a shock to see this system delay further. On top of the onset uncertainty, models are also struggling to handle the depth of the low as it crosses the region, which would have implications on precipitation amounts and potential mountain snow. There remains quite the spread in QPF across ensemble members, with a recent drier trend among many of them. Overall the message remains that there will likely be some sort of cool-down with chances for precipitation by this weekend...but there remain details to be worked out before then. Next week looks favorable for mean troughing to continue across the region with CPC outlooks leaning wetter and cooler. && .AVIATION... SCT-BKN high level cirrus through the forecast period. SFC winds light, terrain driven, and under 10 kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER... Light terrain driven winds mainly under 12 mph through Wednesday with minimum relative humidities of 12 to 22 percent. A low pressure system will likely cross the region by this weekend, though recent trends have shown a delay in its arrival. Current forecast keeps Friday warmer and drier than previously advertised with cooler and wetter conditions arriving Saturday, though may be delayed until Sunday if the system continues to slow. Winds will likely increase and turn southwest with the arrival of the low. && .TWC WATCHES/WARNINGS/ADVISORIES... None. && $$ Public...Edwards Aviation...Edwards Fire Weather....Edwards Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson