Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
289 FXUS65 KTWC 202130 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 230 PM MST Thu Nov 20 2025 .SYNOPSIS... An active pattern continues through this weekend as a second system is expected to arrive late Friday through Sunday. Chances for precipitation hold off for much of southeastern Arizona until Saturday afternoon and evening, though showers may begin to move into western Pima western to central portions of Arizona on Friday. Temperatures remain well below normal with the first widespread freeze expected Friday morning, mainly in the valleys south and east of Tucson. && .DISCUSSION... Broad troughing with multiple embedded shortwaves continued over the southwestern United States this afternoon, with the initial wave exiting southeastern Arizona to the east. Looking upstream another wave was digging south over the southwest coast of California. In-between these waves a brief break in precipitation chances is expected before the second wave arrives, with unseasonably cold temperatures continuing. Friday morning in the wake of the exiting system, sub-freezing morning lows look likely across valleys of Santa Cruz, Cochise, and Graham counties. A Freeze Warning remains in place for these areas. A hard freeze is well within the range of possibilities as NBM probabilities of lows below 28 degrees range from 60 to 90 percent across the Sulphur Springs Valley. The second upper level wave is expected to drop south over the eastern Pacific, west of Baja, through Friday and become positively tilted and closed. Both the positively tilted orientation and closed off process signal a slowing trend in the eventual arrival of this low, and recent model trends have played out as such. Current forecast brings rain chances into western Pima county as early as Friday afternoon then spreads east on Saturday...however can`t rule out the timing nudging a bit slower in the next day. The main brunt of the system is currently forecast to swing through late Saturday through early Sunday with another round of valley rain and high elevation mountain snow showers expected. Snow levels should remain above 7500 feet with 2-5 inches of snow accumulation likely atop mountains. Looking at temperatures there should be a minor warm-up on Saturday before the second weekend system arrives, especially if it delays, then well below normal temperatures are expected Sunday and Monday. Sub-freezing temperatures will return in valleys east and south of Tucson Monday morning. Ridging then takes over early to the middle of next week bringing temperatures back to normal. && .AVIATION...Valid through 22/00Z. SCT-BKN ceilings at 4k-7k feet becoming FEW-SCT through this evening. Isolated showers diminish this evening, linger longest near KSAD and northeastward. Winds become light and terrain driven after 21/03Z. Clouds AOA 15k feet increase from the west after 21/06Z. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER... Below normal temperatures continue through the weekend with minimum relative humidities above 30 percent, with a minor dip to 25 percent in the valleys on Friday as southeastern Arizona will sit between two systems. The second system arrives late Friday through Saturday bringing another round of showers and high elevation mountain snow. Chances for showers remain west of Tucson through Saturday morning, then spread east Saturday afternoon and evening lingering Sunday. Temperatures rise to near normal by the middle of next week. && .TWC WATCHES/WARNINGS/ADVISORIES... Freeze Warning from 2 AM to 9 AM MST Friday for AZZ503-507>509. && $$ Public...Edwards Aviation...Edwards Fire Weather....Edwards Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson