Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX
Issued by NWS Austin/San Antonio, TX
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866 FXUS64 KEWX 051806 AAC AFDEWX Area Forecast Discussion...UPDATED National Weather Service Austin/San Antonio TX Issued by National Weather Service Brownsville TX 106 PM CDT Wed Jun 5 2024 ...New AVIATION... .UPDATE... Issued at 1144 AM CDT Wed Jun 5 2024 With "cold" outflow having ripped through the Austin/San Antonio metro as of 1130 AM, temperatures have dropped sharply (still in the 70s behind it). Traditionally, such outflows "work over" the atmosphere and clean out the "yuck" for several hours following them. Though partial sunshine will return and winds veer back around to light southeast, temperatures will only recover back to the upper 80s to lower 90s and heat index around 100 at best...so have cancelled both the Heat Advisory and Warning east of Medina/Frio Counties. Will need to keep an eye on these counties as well to see if the outflow can power through...though expect it to begin waning as it heads toward the Big Bend/Rio Grande Plains by early afternoon. && .MESOSCALE UPDATE FOR THUNDERSTORM OUTFLOW 1144 AM CDT Wed Jun 5 2024 Outflow winds have been quite robust...and only a little shy of severe levels as indicated by radar and surface obs. Austin gusted to 46 mph and San Antonio/International to 49 mph recently with other gusts on the 30 to 40 mph range. The stronger convection is moving into/off the southeast Texas coast so not expecting severe thunderstorm warnings...but we`ll continue to issue special weather statements to cover the stronger gusts until things quiet down in the next hour or two. && .SHORT TERM... (Today through Thursday) Issued at 253 AM CDT Wed Jun 5 2024 An MCS south of the Red River and a surface boundary extending west into the Permian Basin will track to the south-southeast. The showers and thunderstorms may move across eastern parts of our area (mainly US 77 corridor) this morning, while the surface boundary stalls somewhere near or across our area. This boundary will impact the chances of convection, as well as, the extent of the dangerous heat today into this evening. As for the convection, moisture convergence near the boundary and heating should generate showers and thunderstorms late this afternoon. With upper level ridging beginning to build over our area, areal coverage should be isolated to perhaps widely scattered. Extreme CAPE up to 4,000 J/kg and steep mid level lapse rates of 8 to 9 C/km indicates a potential for a few strong to severe storms, though shear and flow aloft will be weak. The threats are large hail and damaging winds gusts. The showers and thunderstorms will dissipate by late evening with loss of heating after sunset. As far as the heat, expect continued dangerous temperatures and heat indices south of the boundary. High temperatures in the upper 90s to near 102 and heat indices of 108 to 112 are expected around the greater San Antonio area. Although highs of 105 to 109 are expected across the Rio Grande Plains, heat indices will be similar due to mixing of dewpoints. Across both of those areas will issue a Heat Advisory from Noon through 8 PM. High temperatures of 100 to 105 and heat indices of 112 to 114 can be expected across Frio, Atascosa, Karnes, and Wilson counties. Have issued an Excessive Heat Warning for those areas. Temperatures and heat indices will be a bit lower across the Hill Country into Central Texas and no heat products are expected. On Thursday, the upper level ridge becomes more centered over our area. Due to subsidence underneath the ridge and some drying aloft, no convection is expected. Some mixing with this drier air aloft should allow for lower heat indices. However, our southwestern counties may need a Heat Advisory due to the higher heat indices there. Heat Precautions: Never leave people and/or pets alone within a closed car, stay hydrated with plenty of water, wear loose-fitting and light colored clothing, and take frequent breaks within the shade and air conditioning. && .LONG TERM... (Thursday night through Tuesday) Issued at 253 AM CDT Wed Jun 5 2024 The center of the mid-level ridge to our west over Northern Mexico and the Desert Southwest shifts eastward over Texas from Friday into the upcoming weekend. While the hot temperatures are expected to maintain within this pattern, the ridge becoming more centered atop of the region should help to squash any remaining rain/storm chances, delay/limit the extent of the morning low stratus, and promote more efficient atmospheric mixing during the afternoons. This would likely yield to slightly lower afternoon dew points and peak heat indices from Friday through this weekend in comparison from yesterday`s observed values and today`s forecast values. While nights remain quite warm, the overnight lows should also become a little less oppressive as well. The medium range guidance, including the ensemble means, continue with a fairly consistent signal for a potential pattern change into and through early next week. The mid-level ridge will gradually start to buckle as a series of storm systems advance through the northern plains into the Great Lakes region while additional weaker shortwave disturbances advance through the central plains. Models suggest that there could be enough oomph from the parent storm systems for a front to possibly enter portions of Central Texas by sometime around Monday. This front could provide enough forcing for returning low to medium (20-30%) chances for rain and storms. The front and/or any associated cold pool driven mesoscale features may bring enough heat relief to where temperatures trend closer to or even for a few locations perhaps below climatological average at times between Monday and Wednesday of next week. && .AVIATION... (18Z TAFS) Issued at 106 PM CDT Wed Jun 5 2024 Outflow that created gusty northeast winds across the Austin/San Antonio metro has petered out and winds have veered to the east/southeast at the terminals in this corridor. With atmosphere stabilized not expecting any mentionable convection through the afternoon...but do expect to see few-scattered cumulus to redevelop by mid afternoon with mainly scattered cirrus above. For this evening...some models (mainly GFS) hinting at possible quick convection in the corridor but others are very limited...so despite the remining 15-20 percent overall storm probabilities have left out of the overnight TAF. That said...500 mb north/northwest flow with embedded weak short waves is conducive...if atmosphere can recover by late afternoon/early evening. Did not include any light haze/fog for the 08Z-13Z window but something to consider, and did leave a period of low VFR/high MVFR ceilings during this time as well. As for Del Rio...the GFS hints at a potential interaction of the outflow with possible Sierra Madre activity during the early to mid evening but confidence is low in whether this can develop/move into the area. For now, have left out but will need to keep an eye on as well by late afternoon and early this evening. && .CLIMATE... Issued at 253 AM CDT Wed Jun 5 2024 WED THU FRI 06/05 06/06 06/07 ------------------------------------------------ AUS 100/2018 103/2011 100/2022 ATT 101/2011 103/2022* 103/2022 SAT 102/2022 104/2022 104/2022 DRT 107/2022* 110/2022 108/1974 * TIED RECORD WITH MOST RECENT OCCURRENCE SHOWN && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 90 75 97 77 / 10 10 0 0 Austin Bergstrom Intl Airport 91 74 97 75 / 10 10 0 0 New Braunfels Muni Airport 91 75 99 75 / 10 20 0 0 Burnet Muni Airport 90 73 94 72 / 10 10 0 0 Del Rio Intl Airport 108 81 106 82 / 20 20 10 0 Georgetown Muni Airport 90 73 95 74 / 20 10 0 0 Hondo Muni Airport 93 75 101 75 / 10 20 0 0 San Marcos Muni Airport 90 73 97 74 / 10 10 0 0 La Grange - Fayette Regional 90 75 94 74 / 30 10 0 0 San Antonio Intl Airport 91 75 98 77 / 10 20 0 0 Stinson Muni Airport 91 76 100 76 / 10 20 0 0 && .EWX WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM CDT this evening for Dimmit-Kinney- Maverick-Medina-Uvalde-Val Verde-Zavala. Excessive Heat Warning until 8 PM CDT this evening for Frio. && $$ Aviation Update..52/BSG