Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX
Issued by NWS Austin/San Antonio, TX
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323 FXUS64 KEWX 240808 AFDEWX Area Forecast Discussion National Weather Service Austin/San Antonio TX 308 AM CDT Fri May 24 2024 ...New SHORT TERM, LONG TERM, CLIMATE... .SHORT TERM... (Today through Saturday) Issued at 219 AM CDT Fri May 24 2024 Nocturnal stratus continues to increase in coverage across the area overnight. Breezy southeasterly flow also continues with temperatures in the upper 70s to lower 80s. With the cloud cover and wind conditions, lows tonight will not drop much more than current values. 850 temps are slated to warm today much more than yesterday as some weak southwest flow develops in the low-levels. This will allow highs today to warm into the middle 90s in the northeast to the 103-106 degree range out west. Dewpoints will range in the lower to middle 70s for most of the area with lower dewpoints in the Rio Grande and Edwards Plateau as the dryline moves into this region. Where dewpoints remain elevated, afternoon heat index values will range in the 105-110 range and a Heat Advisory is in effect for the central portions of the area between 1 pm and 7 pm. There is a chance of an isolated thunderstorm in the northern CWA late this afternoon and evening as activity moves east off the dryline. Much will be dependent on the strength of the CAP and whether or not we can break it. High-res model guidance is in decent agreement with about a half of the available models showing some convection near the area. Will introduce a 20 PoP late this afternoon and evening for areas north of a Fredericksburg to Austin to Giddings line. If any activity does develop, the atmosphere will easily support severe convection with large hail and damaging winds being the main threats. Significant hail would also be possible given the high CAPE values expected. Low temperatures tonight will be warm once again with lows in the middle to upper 70s once again. High temps will warm again especially in the west as 850 temps increase further. The main question tomorrow will be how much dewpoints can mix out. The NBM keeps dewpoints relatively high over the region but some high res models show some mixing. Regardless, another Heat Advisory will almost certainly be needed for portions of the area tomorrow, but some adjustments the area vs today`s advisory will likely be needed and therefore will handle the Heat Advisories through the weekend one day at a time. && .LONG TERM... (Saturday night through Thursday) Issued at 219 AM CDT Fri May 24 2024 A more stable evening has been in the model consensus for Saturday night, and the same can be said for late Sunday. Time-height sections depict a gradual day-to-day decrease in low level moisture over the weekend with better mixing of dry west winds into the mixing layer and no surface focusing mechanisms to corral what low level moisture still exists. Overnight cooling will again be limited which will punish those spending the holiday weekend in the great outdoors. Sunday and Monday are looking to become the hottest of the days in regards to both ambient temperatures and heat index values. The low to mid level thermal ridge advances farthest east on Sunday, so there`s a chance for DRT to set the all-time record for May on Sunday or Monday. Highest heat index values for the central and eastern counties may come Sunday and the values will potentially warrant an excessive heat warning for parts of the area. The fairly tight mid level zonal pattern over TX relaxes a bit Sunday night as the Central Plains upper troughing pattern pulls away to the NE. This leaves a less stable zonal flow pattern over TX, allowing for possible mid level shortwaves to capitalize on what little Gulf moisture is available. So while the low level thermal ridge is in place over South TX, the ingredients for instability begin to come back together for Monday afternoon. Adding to the destabilization is a weak front moving through North Central TX. It`s not certain what the triggering mechanism is most dominant, but most deterministic model runs depict a return of afternoon storms with the extra hot temperatures likely to help some reach severe levels. Location is not well agreed upon, so a general slight chance is placed over most areas, which favors the GFS in location but not the amount of PoP. The forecast trend collective of MOS guidance does show the 00Z GFS as an outlier, but hopefully that trend will continue in later runs, giving the area some more much needed rain. Nevertheless, will continue running with near record highs assuming not enough areas will be impacted by storm outflows. Slightly better confidence goes into the Tuesday forecast as most models assume the convective outflow influenced push of the front modifies the air enough to weaken the thermal ridge and sent the hotter air back westward. The GFS/ECM seem to 56think there will be a round or two of more formidable shortwaves moving through low latitudes which might suggest some of the better chances for rain seen in several days, at least for the parched southern parts of the forecast area. If nothing else, chances appear low that the heatwave of this weekend will get an extension. && .AVIATION... (06Z TAFS) Issued at 1223 AM CDT Fri May 24 2024 MVFR stratus is in place already at the I35 sites and should see the possibility at DRT closer to daybreak. Can`t rule out brief IFR ceilings at the I35 around morning, but chances were too low to mention at this time. VFR will return by 17-18z for all sites. There is a low chance of a thunderstorm for AUS late tomorrow afternoon or evening. Will leave the forecast dry for now. && .CLIMATE... Issued at 219 AM CDT Fri May 24 2024 FRI SAT SUN MON 05/24 05/25 05/26 05/27 ------------------------------------------------ AUS 99/1955 100/2011 97/2018 100/2011 ATT 104/1925 100/2011 99/2018 100/2011 SAT 101/1989* 103/1989 100/1989 100/2011 DRT 109/2000 104/2011 106/2018 106/2018 * TIED RECORD WITH MOST RECENT OCCURRENCE SHOWN && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 96 75 97 77 / 20 20 0 0 Austin Bergstrom Intl Airport 96 74 97 76 / 20 20 0 0 New Braunfels Muni Airport 98 75 98 77 / 10 10 0 0 Burnet Muni Airport 93 73 94 75 / 20 10 0 10 Del Rio Intl Airport 107 77 108 82 / 0 0 0 0 Georgetown Muni Airport 94 73 95 76 / 20 20 0 0 Hondo Muni Airport 102 75 104 75 / 0 0 0 10 San Marcos Muni Airport 97 74 97 74 / 10 10 0 0 La Grange - Fayette Regional 94 77 95 77 / 0 20 0 0 San Antonio Intl Airport 98 76 99 76 / 0 10 0 0 Stinson Muni Airport 100 77 100 77 / 0 10 0 0 && .EWX WATCHES/WARNINGS/ADVISORIES... Heat Advisory from 1 PM this afternoon to 7 PM CDT this evening for Atascosa-Bastrop-Bexar-Caldwell-Comal-Dimmit-Frio-Gonzales- Guadalupe-Hays-Karnes-Medina-Travis-Wilson-Zavala. && $$ Short-Term...29 Long-Term...18 Aviation...29