Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
101 FXUS65 KTWC 040746 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 1246 AM MST Thu Dec 4 2025 .SYNOPSIS...Cooler temperatures in the wake of an departing weather system that brought light showers to Southeast Arizona Wednesday will result in below normal temperatures across the region through Saturday. Cold morning low temperatures are expected the next few mornings, with widespread sub-freezing temperatures expected in the valleys east and south of Tucson. Otherwise, a ridge of high pressure begins to establish itself into the Desert Southwest Sunday into next week. This will result in afternoon high temperatures warming to above seasonable levels late this weekend into the middle of next week. && .DISCUSSION...The upper pattern this morning is primarily defined by an upper trough of low pressure moving east through northern New Mexico, a trough axis extending from this feature to the SW across far Southeast Arizona, and a positively tilted ridge of high pressure centered near 35N/139W. We continue to see the frontal boundary wash-out as it slowly drags through Cochise county early this morning...with the majority of the light showers observed via KEMX having since tapered off over the past few hours. The positive tilt of the upper ridge in place across the Eastern Pacific will keep the mean trough situated across the Desert Southwest the next few days despite the departure of the main upper low that brought us the light showers yesterday afternoon/ evening. This will reinforce a cool airmass over our neck of the woods with afternoon high temperatures around 5 degrees below seasonable normals both today and Friday. With reduced cloud cover and surface dewpoints falling from the upper 30s to near 40 in the valleys of Southeast Arizona this morning, to the lower 30s Friday morning and mid 20s Saturday morning...we will start to see widespread sub-freezing temperatures take root in the valleys to the east and south of Tucson Friday and Saturday morning. These freezing temperatures will be the first freeze of the season for some of these locations. Therefore, there is a Freeze Warning in effect from 2 am to 9 am MST Friday to highlight the impact of the first freeze. Otherwise, temperatures will begin to rebound and become more mild as we move from Sunday into the middle of next week as the upper ridge amplifies and becomes more of a dominant feature to our west. && .AVIATION...Valid through 05/12Z. SKC west of KTUS and SCT-BKN 5k-8k ft AGL east of KTUS thru 04/17Z clearing from west to east. FEW-SCT 8k-11k ft AGL and SCT-BKN clouds AOA 20k ft AGL mainly from KTUS eastward aft 04/17Z. SFC wind will be variable less than 12 kts thru 04/17Z, then WLY/NWLY around 12 kts this afternoon. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...A cool airmass in the wake of an departing weather system that brought light showers/wetting rains to Southeast Arizona Wednesday will result in below normal temperatures across the region through Saturday. Cold morning low temperatures are expected the next few mornings, with widespread sub-freezing temperatures expected in the valleys east and south of Tucson. 20-foot winds will generally be WLY/NWLY around 10 mph in the afternoon with light terrain driven winds less around 5 mph overnight. Min RH values will be in the 25-35 percent range through Friday, lowering to 20-30 percent this weekend into the middle of next week. Dry weather returns Thursday and persists into the middle of next week. High temperatures will be below normal through Saturday, warming a couple of degrees above normal on Sunday and then 5-8 degrees above normal next week. && .TWC WATCHES/WARNINGS/ADVISORIES... Freeze Warning from 2 AM to 9 AM MST Friday for AZZ503-507>509. && $$ Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson