Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX
Issued by NWS Austin/San Antonio, TX
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138 FXUS64 KEWX 211733 AFDEWX Area Forecast Discussion National Weather Service Austin/San Antonio TX 1233 PM CDT Sat Sep 21 2024 ...New AVIATION... .SHORT TERM... (Today through Sunday) Issued at 300 AM CDT Sat Sep 21 2024 Low clouds are increasing across the eastern part of South Central Texas as of 230 AM CDT. Also, there is a deck of mid level clouds covering the western part of Bexar County that has been around for several hours. Latest nighttime microphysics images are showing some low clouds developing underneath with San Antonio International Airport reporting broken ceiling at 1800 feet. The low level cloud coverage is forecast to remain and expand across most areas through at least 10am - 11am time frame. Overnight lows are forecast to range from the lower 70s across the Hill Country to upper 70s across the Rio Grande and Coastal Plains areas. One more thing, patchy to areas of fog are possible around dawn to about 8-9 am over the Coastal Plains especially over portions of Wilson, Karnes, Gonzales, DeWitt, Lavaca and Fayette Counties. Clouds begin to break late this morning giving way to partly cloudy and mostly sunny skies this afternoon. Highs are forecast to be a few degrees cooler than those on Friday, however, above climate normal values ranging from the upper 80s across the Hill Country to upper 90s along the I-35 corridor and the Coastal Plains. A dry airmass is forecast to push across the eastern part of South Central Texas throughout the day as pwats values come around 1.2 to 1.3 inches and 1000mb - 500mb RH layer at 36 to 38 percent based on the GFS solution. Hires models such as HRRR,NAM 3KM and RRFS also concur. Therefore, the local area should see very limited shower activity if any with 5 to 10 percent chance between U.S. Highway 83 and U.S. HIghway 281 mainly mid to late afternoon. Clouds return during the evening hours and continue developing and spreading through Sunday. An upper level low pressure system is forecast to move across the four corners region today and into the Central Plains by Sunday. A southwest flow aloft is forecast to stay in control over the Rio Grande while a moist southerly wind flow is forecast to prevail late tonight into Sunday morning. This setup could send a few showers across the Rio Grande and parts of the southern Edwards Plateau overnight and Sunday morning. As the day progresses and we enter into the Sunday afternoon period, slight chances for showers are in place for the Coastal Plains and even a shower or two with an isolated thunderstorm is possible over Val Verde County and vicinity as the upper level low pushes to the northeast over the Central Plains while sending a cold front that extends from northeast Texas southwestward to the western part of the state. Sunday`s highs still above climate normal ranging from the upper 80s to mid 90s. && .LONG TERM... (Sunday night through Friday) Issued at 300 AM CDT Sat Sep 21 2024 The upper level low currently over the desert southwest will eventually weaken into an upper trough axis and move east into the central plains states early next week. As the trough axis moves east, a cold front is expected to move southward early Monday and should be near a Rocksprings to Llano line around sunrise Monday. With some weak lift and low-level forcing along the front, rain chances will be in the forecast late Sunday into Monday across the southern Edwards and Hill Country. The latest guidance has trended a little stronger with the frontal boundary and rain chances have trended upward across the southern Edwards Plateau. The front is expected to gradually slide southward during the daytime hours on Monday. The models are fairly reluctant to develop much in the way of convection during the afternoon hours along the front and rain chances still look to remain favored over the Hill Country. In addition, some isolated afternoon convection may develop over the coastal plains as the sea breeze moves inland. Temperatures will trend downward slightly for most of the region, with the most notable drop in the Hill Country and southern Edwards Plateau. On Tuesday, a reinforcing shot of upper level energy is expected to drop southward out of the southern Rockies and help reinforce the upper level trough. The models differ with the speed and strength of this upper level energy, so there will be some uncertainty in the forecast. For now, we will keep rain chances in the forecast for most of south central Texas, with the focus for better rain chances still favored for areas generally west of I-35. We will also need to maintain an eye on the northwestern Caribbean or southern Gulf of Mexico as the last few NHC outlooks maintain an increasing probability for tropical development in the mentioned region. Uncertainty continues through the remainder of the forecast as much will depend on the development of an upper level trough or perhaps a closed low over the southern U.S. plains and the expected tropical system in the Gulf of Mexico. For now, we will keep some low rain chances in the forecast for most of the region along with near to slightly above normal temperatures. && .AVIATION... (18Z TAFS) Issued at 1227 PM CDT Sat Sep 21 2024 Expect remaining MVFR to lift and thin to VFR by 20Z at all sites. South to Southeasterly flow will persist at all sites through the forecast period, with gusts to 20-22 KT at times for KAUS and KDRT this afternoon. Look for CIGS to develop and fall starting around 06-09Z, with MVFR CIGS expected at all locations from 09-15Z. There may be some BCFG from 10-15Z, but that is not expected to impact operations. CIGS will lift but be very slow to become SCT on Sunday. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 75 96 74 93 / 0 0 10 10 Austin Bergstrom Intl Airport 73 95 73 93 / 0 0 0 10 New Braunfels Muni Airport 74 96 73 95 / 0 0 0 10 Burnet Muni Airport 73 92 71 87 / 0 0 20 20 Del Rio Intl Airport 79 95 76 91 / 10 0 30 40 Georgetown Muni Airport 73 94 73 90 / 0 0 10 10 Hondo Muni Airport 74 94 72 93 / 0 0 10 10 San Marcos Muni Airport 73 94 71 93 / 0 0 0 10 La Grange - Fayette Regional 73 94 72 93 / 0 0 0 10 San Antonio Intl Airport 76 94 75 93 / 0 0 10 10 Stinson Muni Airport 76 95 74 96 / 0 0 0 10 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term...Zeitler Long-Term...MMM Aviation...Zeitler