Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
945 FXUS65 KTWC 192129 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 229 PM MST Wed Nov 19 2025 .SYNOPSIS...A low pressure system will cross the region over the next several days bringing cooler temperatures, chances for precipitation including snowfall above 7000 feet, and breezy conditions. Showers will be isolated to scattered through early this afternoon, becoming more numerous this evening into Thursday morning. Temperatures will become well below normal Thursday with the first widespread freeze expected Friday morning, mainly in valleys to the south and east of Tucson. && .DISCUSSION...Isolated to scattered showers and a few thunderstorms have developed across southeast Arizona this afternoon associated with a potent storm system moving across the Desert Southwest. The presence of modest moisture and instability (precipitable water values around three-quarters of an inch, CAPE around 500 J/kg, and elevated mid- level lapse rates) has supported a couple instances of smaller hail (pea to nickel-sized), brief heavy rainfall, and lightning. Additional showers will continue to evolve into the evening and overnight hours with increasing potential for high elevation mountain snow. Storm total rainfall through tomorrow will mostly range between one-quarter of an inch to three-quarters of an inch, but pockets of higher amounts can be expected where showers move over the same area or are influenced by terrain. Snow levels this evening will progressively lower as colder air advances with the storm system. Snow levels this afternoon will start between 8500-9500 feet before lowering to 6500-7500 feet by early tomorrow morning. Total snow through tomorrow will generally range be between 2-6 inches above 7500 feet with isolated amounts over 6 inches in the White Mountains and on Mount Graham. Only minor impacts are expected and for higher elevations from this quick moving system, so I held off on issuing a winter weather headline. After the storm system passes the forecast focus shifts to the cooler air settling in behind as the trough quickly ejects into the southern and central Rockies. Chances have been gradually increasing (Now 60-90%) for subfreezing temperatures to the south and east of Tucson on Friday morning. As cloud cover clears, winds subside, and cool air settles into the valleys to the east and south of Tucson, temperatures will bottom out into the mid to upper 20s. I lowered temperatures for the Sulphur Springs Valley, San Pedro River Valley, and in the vicinity of Sonoita and Patagonia and issued a Freeze Warning for these locales as well from 2 AM to 9 AM MST Friday morning. Remember to protect people, pets, pipes, and plants from freezing temperatures. With mean troughing remaining in place to our west, I look upstream and see another upper-low currently in the Gulf of Alaska. This system will dive along the same path toward SRN CA/NRN Baja by Saturday morning before ejecting across our neck of the woods this weekend. This would bring another round of valley rain/mountain snow, breezy winds, and reinforcement of the cold temperatures in place across the area. && .AVIATION...Valid through 21/00Z. SCT-BKN 4k-7k foot ceilings becoming BKN-OVC after 19/21Z. Isolated to scattered showers with isolated thunderstorms this afternoon, becoming widely scattered with isolated thunderstorms after 20/00Z. Visibility reductions and lowered ceilings with mountain obscurations may bring periods of MVFR or near MVFR conditions, especially after 20/02Z. Isolated showers with reduced coverage after 20/12Z. Surface winds turn southwesterly 10-15 kts this afternoon with gusts to 25 kts, then become more southerly 7-12 kts after 20/02Z. Winds turn southwest again after 20/12Z. && .FIRE WEATHER...A storm system will continue to impact Southeast Arizona this afternoon through Thursday. This system will bring numerous showers with a slight chance of thunderstorms, snowfall to the mountains above 7000 feet, well below normal temperatures and breezy south to southwest winds. Minimum RH values will be well above critical levels over the next week between 35-45 percent in the valleys and 65-75+ percent in the mountains. && .TWC WATCHES/WARNINGS/ADVISORIES... Freeze Warning from 2 AM to 9 AM MST Friday for AZZ503-507>509. && $$ Public...DVS Aviation...AE Fire Weather...DVS Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson