Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX
Issued by NWS Austin/San Antonio, TX
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240 FXUS64 KEWX 220833 AFDEWX Area Forecast Discussion National Weather Service Austin/San Antonio TX 333 AM CDT Wed May 22 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (Today through Thursday) Issued at 155 AM CDT Wed May 22 2024 * Level 2 to 3 out of 5 risk for isolated to scattered severe storms this evening across portions of the northern Hill Country and central Texas. * Dangerous heat indices this afternoon - those spending extended time outdoors and not acclimated to the early season heat could be susceptible to heat related illness if not taking proper heat precautions. Nocturnal stratus has developed across south-central Texas and will scatter out midday. In addition, hazy conditions, associated with seasonal smoke from agricultural burning to the south, persists across our region and will continue east of the dryline through the short-term. The upper level ridge axis has shifted into the southeast U.S. and western Gulf of Mexico. This will open the door for convective initiation along a weak cold front over north-central Texas and along the dryline just to the west in the higher terrain of Mexico this afternoon. There is a low chance (20%) that an isolated storm or two could cross the Rio Grande into Val Verde, Kinney, or Maverick Counties between 4PM and 7PM today. However, the bigger chance (30-40%) of storms will be across the northern forecast area this evening. CAMs indicate the aforementioned storms that develop along the front to the north moving east-southeast into Llano and Burnet Counties 7PM to 10PM, and potential as far south as the Austin metro area after 10PM. There is a Level 2 to 3 out of 5 risk for severe storms across these areas this evening, with large to very large hail and damaging wind gusts the primary threats. An isolated tornado can`t be ruled out, mainly in the Level 3 risk area across Llano and Burnet Counties. this afternoon Farther south, convective inhibition will be increasing out of the Coastal Plains and into portions of the I-35 corridor late evening, and we anticipate a weakening trend of the storms at that time, eventually dissipating. We do not currently expect the storms to reach the San Antonio metro area or Coastal Plains. On Thursday the dryline makes a slightly farther east progression. With the surface cold front washed out to the north, forcing will be weaker and convective coverage less. There is a very low (10-20%) chance of an isolated storm or two late Thursday afternoon across Llano and Burnet Counties. Otherwise, continued well above normal temperatures today and Thursday. Heat indices today to the south and southwest of the San Antonio metro area are forecast to reach advisory criteria, and a Heat Advisory will be issued. The elevated dew points east of the dryline, influences from evapotranspiration where better spring rainfall has occurred, and early nature of the summer heat will result in an increased risk for heat impacts. Those spending extended time outdoors and not acclimated to the early season heat could be susceptible to heat related illness if not taking proper heat precautions. && .LONG TERM... (Thursday night through Tuesday) Issued at 155 AM CDT Wed May 22 2024 * Dangerous heat indices and hot temperatures will continue to worsen into the Memorial Day Weekend - those spending extended time outdoors and not acclimated to the early season heat could be susceptible to heat related illness if not taking proper heat precautions. A compact upper low moving into the Northern Plains states helps to shape the Central and Southern Plains surface pattern with a more stable flat zonal pattern over TX by 00Z Friday. This has us pulling back on the already low chances for convection for the period Thursday night through Friday night. There is still a deterministic signal for some isolated Central TX convection to crop up again for the PM hours Friday, but this pattern looks closer to the one we saw Tuesday evening: 1 severe storm and well to the north of our CWA. By comparison to the SPC Day2 Outlook, the small area of general thunder over our northern counties for the Day3 Outlook shows an appropriate level of concern for what was previously another possible round of rain, still much needed over the Hill Country. Fast forward to the other side of the heat wave and a weakness in the flat ridging over TX and a possible weak cold front could bring our next possible chance for isolated to scattered storms. Cold fronts in late May over South Central Texas are somewhat a rarity, so the confidence is going to remain low that we`ll see anything but another escalation of our drought conditions in what looks to be another projected drier than normal summer. Temperatures and heat indices are thus the primary hazard concern for the Memorial Day weekend. Heat products will likely be needed for each day through Monday, and the potential will exist for some areas to need an Excessive Heat Warning Friday through Monday. this afternoon this afternoon Thanks to a generous rainfall pattern over Central TX, the Austin metro area will possibly stay out of the triple digits during this period, but a drier heat on Sunday could get the first triple digit day for that area. The San Antonio and New Braunfels areas have already flirted with triple digit heat and the drier soil and vegetation there could bring that into the picture as early as Friday. In general, the eastern half of the forecast area will be reaching the advisory (or worse) conditions based on the Heat Index. Farther west, a more dry heat is projected. While RH values overachieved to hold down the max over much of the western counties Tuesday, the progressively hot and dry days under this zonal pattern will bring the thermal ridge a little farther east each day and mixing out the morning clouds with more efficiency as we approach the weekend. The metro cities could see near record temperatures over the weekend, but with the drier heat over the western counties the chance for high temperature records for DRT will be much higher. On May 10th, the Monthly max for May at DRT was already tied, so we should expect to see a new monthly record to be set in this pattern. Finally on Memorial Day, a cold front is expected to push into North and Central TX. This could pull back on some of the heating potential around AUS, but compressional heating could bring the climate sites near Highway 90 close the values seen Saturday and Sunday. Cooler maxes are projected for Tuesday and next Wednesday, and hopefully some rain and moisture will thwart the return of more heat waves until we get deeper into the summer season. && .AVIATION... (06Z TAFS) Issued at 1235 AM CDT Wed May 22 2024 Stratus is quickly developing across the Coastal Plains, I-35 corridor, and Hill Country, and is forecast to expand west into the Rio Grande early Wednesday morning. Mainly MVFR ceilings are expected, although some isolated pockets of IFR ceilings can`t be ruled out over the Hill Country. In addition, visibility will be reduced to MVFR in some spots overnight and Wednesday morning in a mixture of BR and HZ. Ceilings are forecast to scatter out 15Z-17Z, with VFR conditions through the afternoon, but 6SM visibility in HZ for some locations. Finally, isolated TSRA are forecast to develop in Mexico after 21Z, and there is a low probability (20%) of storms moving across the Rio Grande 21Z-03Z. The better chances for storms will develop after 21Z across north-central and may enter northern areas of south-central Texas after 00Z Thu. There is a 30% chance of TSRAs reaching AUS Wednesday evening. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 94 76 94 76 / 10 30 10 0 Austin Bergstrom Intl Airport 94 75 93 76 / 10 30 10 0 New Braunfels Muni Airport 97 76 97 76 / 10 10 10 0 Burnet Muni Airport 91 73 91 74 / 30 40 20 0 Del Rio Intl Airport 104 81 106 80 / 10 20 0 0 Georgetown Muni Airport 93 73 92 75 / 20 40 10 0 Hondo Muni Airport 99 75 100 74 / 10 10 0 0 San Marcos Muni Airport 95 75 96 75 / 10 20 10 0 La Grange - Fayette Regional 92 77 92 77 / 10 10 0 0 San Antonio Intl Airport 96 77 97 76 / 10 10 10 0 Stinson Muni Airport 97 77 98 77 / 10 10 0 0 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term...76 Long-Term...18 Aviation...76