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Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
535 FXUS65 KTWC 061610 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 910 AM MST Sat Jul 6 2024 .SYNOPSIS...Excessive heat and hot temperatures through at least 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. && .UPDATE...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 1-2 degrees cooler compared to this time 24 hours ago...which matches up well with our forecast high today of 109 degrees. The NBM probability for KTUS to meet or exceed 110 degrees is 20% today, increasing to 55%/50%/55% 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 this morning, with the extreme SE periphery of this feature extending across the majority of SE AZ. The generalized warming that will occur today at 500 mb as this feature moves slowly SE will warm/erode away some of the CAPE available to us on the 06/12Z KTWC upper air sounding...significantly limiting the potential for thunderstorms across the majority of our neck of the woods. However, an area of very weak diffluence is noted in the Whites, and across eastern Cochise county extending WSW into northern Sonora. The Whites will likely be too dry to get active today although a weak storm will be possible in northern Greenlee county. The best location for storm development will be the SE half of Cochise today, were CAMS and WRF runs consistently showing isolated thunderstorm activity. 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 SE Cochise. && .PREV DISCUSSION... /issued 202 AM MST Sat Jul 6 2024/ .DISCUSSION...Very little change in the forecast pattern and thinking versus 24 hours ago. A strong ridge of high pressure was currently centered over the northern California coast. This ridge will build slowly southeast through early next week, when it will be centered along the AZ/CA/NV borders. The models then show the high lifting northeast into Utah mid to late next week. This pattern will result in hot daytime temperatures and a low grade monsoon through early next week, with deeper moisture moving back into the region mid to late next week. The main story continues to be the EXCESSIVE HEAT and HOT daytime temperatures across southeast Arizona, with near record to record high temperatures. Have decided to extend the Excessive Heat (EH) Warning out through 8 pm MST Tuesday of next week. It may still need to go out even further depending upon how quickly moisture moves back into southern Arizona. At this time, the Excessive Heat Warning is in effect for all but Santa Cruz and Cochise counties and the mountain zones of southeast Arizona. During this time frame monsoon activity will be limited to mainly south/southeast of Tucson, across Santa Cruz and Cochise counties as the deeper moisture gets pushed south into northern Mexico and high pressure builds in from the northwest. GOES-16 Total Precipitable Water (PW) Imagery shows values currently around 0.67 inches in Tucson (0.81 inches on the KWTC 240706/00Z sounding), with 1.0-1.2 inches along the International Border and a very dry 0.20 inches in the White Mountains. The ensemble models indicate PW values will continue to lower through the weekend into early next week, when PW values will range from around 0.25 inches in the White Mountains to 0.5-0.7 inches across the rest of southeast Arizona and even much of northern Mexico. As the high shifts north and then northeast of the region mid to late next week, a more favorable moisture pattern returns to southeast Arizona and expect shower and thunderstorm chances to increase, as well as high temperatures to slowly decrease (but still remaining several degrees above normal levels). Model PW`s rebound to around 1" late next week. By next weekend, the models have the high centered over Colorado, with deep south/southeast flow across Arizona and PW`s increasing to 1.25-1.50" across southeast Arizona. && .AVIATION...Valid through 07/12Z. FEW-SCT clouds at 13k-15K ft AGL and BKN-OVC clouds AOA 20k ft AGL southeast of a Sells to KTUS to KSAD line thru 06/15Z, then diminishing cloud cover. Clear skies elsewhere. Between 06/18Z and 07/05Z, SCT-BKN clouds at 7k-10k ft AGL and ISOLD-SCT TSRA/SHRA mainly south and east of KTUS. MVFR conditions near TSRA, with mountain obscurations, VSBY restrictions and gusts to 40+ kts. Aft 07/05Z, gradual clearing thru the remainder of the forecast period. 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...There will be the daily chance for isolated to scattered showers and thunderstorms mainly from Tucson south and east into early next week. High pressure aloft will build to our northwest through the weekend into early next week, which will result in hot conditions. With the hotter temperatures and some of the deeper moisture getting pushed to the south and east 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. Hot high temperature are expected through at least Tuesday, 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. Excessive Heat will be an issue during this time frame. 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 Rover valley near Safford on Sunday where northwest winds of 20-25 mph and higher gusts are expected. Early next week elevated wind speeds in the 15-20 mph range will be possible mainly to the east of Tucson. && .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