Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
008 FXUS65 KTWC 111702 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 1002 AM MST Thu Jul 11 2024 .SYNOPSIS...Excessive heat continues across southeast Arizona today before thunderstorms develop later this afternoon. Scattered thunderstorms are expected to develop and move through the area this afternoon and evening, with the potential for severe and damaging wind gusts. Additional monsoon activity over southeastern Arizona will be possible going into this weekend and early next week. && .UPDATE...Rather hazy/dusty morning across southeast Arizona with visibilities down in the 1 to 3 mile range. Not completely sure where the haze/dust came from but we did have outflows move across the area from the east and south last night. Visible imagery showed clear sky across the entire area with PW values up a smidge from this time yesterday, in the 0.8" east to 1.2" west. At the surface, dewpoints were mostly in the 50s. On the Tucson 12z sounding, mid-level flow has turned to the N/NE with expected turn to the NE this afternoon. This NE steering flow will allow t-storms that develop over the mountains, especially the Whites, to propagate SW across the forecast area this afternoon into this evening. Severe wind gust potential is up under this rim shot regime, especially considering the hot boundary layer that exists and likely inverted-V profiles, SPC has areas west of Clifton to Douglas line in slight risk for severe wind. 11/12z HREF is highlighting parts of SE AZ including Tucson metro with 30% chance of wind gusts in excess of 50 kts within 25 miles of a given point. In coordination with WFO Phoenix, went ahead an issued a blowing dust advisory from 4 pm to 8pm to handle any dust that is generated by t-storm outflows. Can`t rule out a dust warning late this afternoon. Oh yeah, almost forgot. Another hot day with Excessive Heat Warning expiring at 8 pm. See previous discussion below for additional forecast details into early next week. && .PREV DISCUSSION... /issued 318 AM MST Thu Jul 11 2024/ In the mid to upper levels, a high was centered over southern Nevada/Utah and mean 700-300mb flow over southeastern Arizona was becoming northeasterly in turn. Under strong surface heating and modestly increasing low to mid level moisture today, convection forming off higher terrain and the Mogollon Rim should spread across southeastern Arizona this afternoon and evening. Increased mid-level flow should allow for longer lasting convective cells, which combined with the deeply mixed boundary layer will produce a threat of severe and damaging wind gusts. The 00Z convective allowing model suite remains bullish on severe wind gust potential as much of southeastern Arizona is painted with a 30 percent probability of a 50 kt wind gust within 25 miles of a point. The updraft helicity probability also shows CAMs are attempting to resolve minor thunderstorm rotation, which would add to the wind gust potential if thunderstorms become more organized and long lived. In collaboration with SPC, a Slight Risk based off the wind threat was introduced in SPC`s day one outlook for today. The Excessive Heat warning remains in effect into this early evening, as strong surface heating and the influence of the upper ridge will lead to another day of above normal highs. Some areas, especially near terrain or in Graham and Greenlee counties closer to the Whites, temperatures may cool quicker this afternoon after convection develops. Until this occurs Heat Risk will remain on the high side. Highs should trend down closer to normal over the next several days as the pattern switches back to a more active monsoon setup. Convective potential Friday should depend somewhat on how the atmosphere recovers after today, which may delay convection until it moves off the higher terrain closer to the evening. Additionally, some 00Z guidance is indicating instability and better convective potential may lie west of Tucson, though forecast chances remain spread across southeastern Arizona for now given uncertainty with the impact of previous convection. Under favorable easterly flow, each day from this weekend into early next week carries a chance of monsoon activity. There remains uncertainty on which days may be more active compared to others, with at this moment Sunday-Monday still looking like more active days based on ensemble moisture and QPF probabilities. && .AVIATION...Valid through 12/12Z. Isolated thunderstorms expected to begin developing 11/18Z - 11/21Z then becoming more widespread after 21Z. Thunderstorms will develop off higher terrain and move south-southwesterly across much of southeastern Arizona. Strong outflow gusts to around 50 kts possible with any thunderstorm and a few may produce even higher gusts. Thunderstorm activity should persist longer into the evening in southern areas, then should be clearing after 12/05Z. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Daily chances for thunderstorms across southeast Arizona are expected going into next week, with day to day variation in location or coverage. Today, scattered thunderstorms with the potential for very strong outflow winds will move through southeastern Arizona. Minimum relative humidities this afternoon and tomorrow will range from 10 to 16 percent in the lower elevations and 15 to 30 percent in mountain areas. Humidity values increase this weekend as greater moisture returns. Away from thunderstorms, 20 foot winds of 12 to 16 mph with gusts to around 25 mph are expected each day with light and terrain driven winds overnight. && .CLIMATE...Near record to record high temperatures today. DATE Jul 11 FCST RCD/YR TUCSON INTL AIRPORT 110 111/1958 PICACHO PEAK 111 112/1998 SIERRA VISTA FD 99 103/2020 && && .TWC WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning until 8 PM MST this evening for AZZ501>506-509. && $$ Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson