Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
074 FXUS65 KTWC 041002 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 302 AM MST Mon May 4 2026 .SYNOPSIS... A Pacific storm system will approach and cross the region through Wednesday. Breezy winds are expected today and Tuesday with this system, as well as a chance of showers and thunderstorms from this evening through Tuesday. High temperatures are expected to fall below normal Tuesday and Wednesday, then rise back above normal the latter half of the week. Well above normal temperatures are likely by this weekend. && .DISCUSSION... A closed low sitting over the California coast this morning will gradually open and cross the region eastward over the coming several days. Sub-tropical moisture streaming through the base of this low has provided cirrus coverage over southeastern Arizona with increasing precipitable water values. Shower chances begin to increase this evening (a few can`t be ruled out late this afternoon) as the upper low approaches. Shower coverage should transition from west to east through Tuesday morning as the associated low level front moves into the region, with additional chances Tuesday afternoon with isolated to scattered convection. Overall coverage however remains somewhat uncertain as synoptic support from the incoming upper level jet will be misplaced to the north from the low level front. 00Z high resolution models highlight this problem with disagreement between the 00Z HRRR delaying showers a good 3-6 hours behind other models in the HREF suite. Overall, greatest chances for showers is from late this evening through early Tuesday morning, then spotty convection will be possible Tuesday afternoon mainly east and north of Tucson. The aforementioned mismatch of low and upper level features will also keep rainfall totals light, generally 0.01-0.2 inches in the valleys and up to 0.5 inches in the mountains, with greater totals possible in the Catalinas, Rincons, Pinalenos, and White mountains. Breezy winds out of the southwest today and Tuesday with cooler temperatures Tuesday and Wednesday will accompany this system, both maximizing on Tuesday. 15-20 mph winds and gusts to 35 mph will be common Tuesday afternoon (mainly east of central Pima) with stronger winds across portions of Santa Cruz and Cochise county where gusts to 40 mph will be possible. Forecast high temperatures today will be about 2-4 degrees below normal, then 4-10 degrees below normal Tuesday and Wednesday. Some guidance continues to show lingering circulation aloft on Thursday, which may keep some moisture in the area with the low-end chance of a shower. However the overall trend will still favor warming and drying conditions with well above normal temperatures likely by this weekend. && .AVIATION...Valid through 05/12Z. BKN-OVC cirrus AOA 20k feet with FEW-SCT 15k foot ceilings, then FEW-SCT 10k-15k ceilings after 04/12Z. Further lowering of ceilings likely as a front moves into the region from the west after 05/03Z, along with isolated to scattered rain showers. These showers should move through KTUS-KOLS-KSAD in a window from 05/03Z-05/12Z, and KDUG around 05/10Z-05/15Z, though there remains some uncertainty in the timing of their development as well as their coverage. Winds out of the southwest will increase after 04/16Z and become 12-18 kts with gusts to 25 kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER... A Pacific storm system will continue to approach the region today, increasing southwesterly winds this afternoon to 15-20 mph with gusts to 35 mph. As the system crosses on Tuesday winds will increase to 18-25 mph with gusts up to 40 mph, especially from Santa Cruz eastward through southern Cochise county. Moisture will increase with incoming chances for showers and a few thunderstorms from this evening through Tuesday. Minimum relative humidity in the valleys today will be 15-20 percent and 20-30 percent in the mountains, increasing to above 20 percent in the valleys and above 30 percent in the mountains on Tuesday. Temperatures 4-10 degrees below normal arrive with this system Tuesday and Wednesday. Relative humidity quickly dries out the second half of the week from Wednesday onwards. Well above normal temperatures are expected by the weekend. && .TWC WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Edwards AVIATION...Edwards FIRE WEATHER...Edwards Visit us on Facebook, X, YouTube, and at weather.gov/Tucson