Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
392 FXUS65 KTWC 220908 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 208 AM MST Thu May 22 2025 .SYNOPSIS...A building ridge of high pressure across the region will result in hot conditions across Southeast Arizona today, with afternoon high temperatures 7 to 10 degrees above climatological normal. Otherwise, light winds with occasional afternoon gustiness due to strong heating can be expected today, with breezy afternoon winds returning Friday. && .DISCUSSION...The upper pattern this morning is defined by a broad ridge of high pressure across Northwest Mexico extending into the Desert Southwest. This should result in hot conditions across the forecast area today, with 850-700 mb thickness values around 1675m, resulting in an afternoon high temperature at the Tucson International Airport (KTUS) between 101-104 degrees. In general, expect afternoon temperatures approximately 100-104 degrees from Tucson westward (and upper Gila River Valley) and in the 90s across the eastern valleys. These temperatures will result in a `Moderate` HeatRisk today...so as I mentioned yesterday, make sure to check in on those individuals that are sensitive to heat, making sure they have adequate cooling and are staying hydrated. A dry trough of low pressure developing along the West Coast today will begin to amplify the upper pattern as it tracks east through the Great Basin into this weekend. The southern periphery of this feature will drag through Southeast Arizona Friday, resulting in breezy southwest winds 15 to 25 mph with gusts to 30-35 mph. At this time, winds should stay below critical fire weather thresholds...but it should be noted that brief, near critical conditions will be possible. The 22/00Z Hot Dry and Windy Index (HDWI) values indicate that 20-40 percent of the GEFS members will meet or exceed the 95th percentile Friday. Usually, I would like to see percentage of GEFS members above 50 percent (more like 60-80 percent) before considering any fire weather headlines so I feel comfortable not having one out despite ERC values for Southeast Arizona above the 90th percentile. The upper trough slowly moves east across our neck of the woods Sunday with a shortwave ridge in its wake moving into a position across the Southern Rockies/New Mexico next week. A ridge in this location will result in a south to southeast mid-level flow across the eastern half of the CWA. This mid-level flow will tap into deeper moisture across SW Texas and NE Mexico resulting in the western periphery of the 850-700mb Theta-E ridge nudging into Cochise, Graham and Greenlee counties Tuesday through Thursday. Both operational runs of the 22/00Z GFS and 22/00Z ECMWF have maximum Theta-E differences between 0-6km greater than 10K, which indicates there is enough instability for elevated convection across the eastern zones, especially Wednesday. Given the dry sub- cloud layer, any convection will likely be in the form of dry thunderstorms with the potential for gusty and erratic outflows near the evaporating downdrafts. && .AVIATION...Valid through 23/12Z. SKC thru the day Thursday, with SCT-BKN cirrus clouds AOA 20-25k ft AGL moving into the area from the west during the evening and overnight hours (AFT 23/00Z). SFC winds generally terrain driven less than 10 kts this morning, becoming SWLY/WLY 10-15 kts with occasional gusts to 20 kts in the afternoon due to significant heating. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...A building ridge of high pressure across the region will result in hot conditions today across Southeast Arizona. Expect afternoon high temperatures 100-104 degrees from Tucson westward (and upper Gila River Valley) and in the 90s across the eastern valleys. Although occasionally gusty winds will be observed due to the significant surface heating the next several days, the strongest winds will occur Friday as a dry disturbance tracks across the area. At this time, wind speeds should stay below critical fire weather thresholds (Southwest 15-20 mph with gusts to 30-35 mph). Single digit min RH values at all elevations over the next week with poor overnight recoveries. There is the potential for some mid-level moisture to move into far eastern areas (east of Tucson) by the middle of next week. This may lead to some afternoon buildups and/or isolated dry lightning strikes Tuesday and Wednesday of next week. && .TWC WATCHES/WARNINGS/ADVISORIES...None. && $$ Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson