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Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
289 FXUS65 KTWC 062108 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 208 PM MST Sat Jul 6 2024 .SYNOPSIS...Excessive heat and hot temperatures through Tuesday, with high temperatures expected to approach record levels in some locations. Shower and thunderstorm chances will mainly be confined to south and east of Tucson through early next week as drier air overspreads Arizona from the north. Thunderstorm activity will begin to ramp back-up the middle of next week. && .DISCUSSION...The main weather story/impact for Southeast Arizona the next several days reminds me of the time I ordered some hot wings...hot with a side of hot sauce. Not a pleasant experience to say the least. Unfortunately, that is what we have to deal with today as excessive heat continues to have a stronghold on the area. Yesterday, the Tucson International Airport was able to tie a daily max temperature record of 111 degrees and we can expect more of the same today. I guess the good news is that across the region, we are running 0-2 degrees cooler compared to this time 24 hours ago...which matches up well with our forecast high today of 109 degrees. The 06/13Z NBM probability for KTUS to meet or exceed 110 degrees is 20% today, increasing to 50%/55%/45% for Monday/Tuesday/Wednesday. Yuck. With regards to storm coverage today, things are shaping up to be fairly quiet for the forecast area. The upper pattern is dominated by a strong ridge of high pressure aloft centered over northern California, with the extreme SE periphery of this feature extending into SE AZ. The generalized warming that will occur today at 500 mb as this feature moves slowly SE has warmed/eroded away some of the CAPE available to us on the 06/12Z KTWC upper air sounding, limiting the potential for thunderstorms across the majority of our neck of the woods. However, an area of very weak diffluence aloft is noted in the White Mountains and along the Arizona/New Mexico border extending WSW into northern Sonora. As of 2 PM MST, the White Mountains have seen some weak thunderstorm development but are struggling to develop into anything significant due to the drier airmass. The best location for storm development will be along the southern Arizona/New Mexico border and across the southeast half of Cochise. Given the hot and relatively dry sub-cloud layer, the main threat from these storms will be strong and gusty outflow winds. This matches up well with the 06/12Z HREF area of 50-70% likelihood for outflows in excess of 30 kts along the southern Arizona/New Mexico border and even a near 10% chance of outflow winds in excess of 50 kts in NM bordering our CWA. However, organized outflows that do develop will generally push SSW into NE Sonora/NW Chihuahua Mexico this afternoon, just clipping southeast Cochise county. As the upper high drifts slowly SE the next few days this will further stabilize the atmosphere aloft significantly limiting the chance of pcpn across SE AZ. The H5 center makes its way into SE CA Monday afternoon then begins to positively tilt and move toward NW AZ by the middle of next week. This will increase our thunderstorm activity as we not only start to import deeper moisture from the east/northeast but it as also a favorable flow for storms to move storms off the higher terrain near the Mogollon Rim downhill toward the lower elevations/Tucson Metro in the late afternoon/evening. Although ensemble members suggest a bigger dayto occur Wednesday, experience suggests that it is the transition days (Tuesday) that are the most active days as we will be experiencing the excessive heat during the day followed by strong storms moving down off the rim in the evening. Given this pattern change, I am very hesitant to extend the Excessive Heat Warning into Wednesday and Thursday even though the NBM probabilities for KTUS reaching 110 degrees is 45% both days. There is just too much change going on and with deeper moisture within arms-reach, it will make it that much more difficult to get that hot. In any event, HOT conditions will be around well into the upcoming work week. && .AVIATION...Valid through 08/00Z. SKC-SCT clouds at 8k-12K ft AGL becoming SCT-BKN clouds at 7k-10k ft AGL and ISOLD-SCT TSRA/SHRA along the Arizona/New Mexico State line in the mid-late afternoon. MVFR conditions near TSRA, with mountain obscurations, VSBY restrictions and gusts to 40+ kts. Aft 07/05Z, gradual clearing thru the Sunday morning. Outside of TSRA outflows, SFC wind 12 kts or less favoring a WLY/NWLY direction during the afternoon/early evening hours and variable in direction at other times. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Hot with a daily chance for isolated to scattered showers and thunderstorms south and east of Tucson into early next week. Excessive heat will be an issue during this time frame with highs 106-113 degrees from Tucson westward and in the Gila River Valley, and in the upper 90s to 105 degrees across Santa Cruz and Cochise counties. With hot temperatures and deeper moisture getting pushed to the south of the region, min RH values will lower into the 10-17% range across the lower elevations and 14-25% in the higher elevations into the middle of next week. Outside of any thunderstorm outflow winds, 20-foot winds will generally be 15 mph or less each afternoon with occasional gusts to 20-25 mph through the weekend. The exception will be in the upper Gila River valley near Safford on Sunday where northwest winds of 20-25 mph and higher gusts are expected. && .TWC WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning until 8 PM MST Tuesday for AZZ501-502- 504>506-509. && $$ Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson