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Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX
Issued by NWS Austin/San Antonio, TX
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818 FXUS64 KEWX 180743 AFDEWX Area Forecast Discussion National Weather Service Austin/San Antonio TX 243 AM CDT Tue Jun 18 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (Today through Wednesday) Issued at 204 AM CDT Tue Jun 18 2024 Key Points... *Bands of moderate to heavy rains expected to begin early Wednesday and continue into Thursday. *A Flood Watch has been issued beginning Wednesday morning and continuing through Thursday midday. Deep tropical moisture with PWs above 2 inches is lurking offshore over the Gulf of Mexico early this morning. As potential Tropical Cyclone One develops, this moisture will surge across the Coastal Plains today and over South Central Texas tonight into Wednesday as the potential cyclone approaches the northeastern Mexican coast. This is due to a relative weakness in the Subtropical Ridge over Texas. With the initial increase in moisture, streamer showers can be expected this morning. Then, as the moisture deepens further, showers and thunderstorms will spread from the Coastal Plains late this morning to near the I-35 corridor this afternoon into early evening. The increase in moisture and associated cloudiness should keep high temperatures closer to normal today. The showers and thunderstorms will taper off this evening. As the slug of deep tropical moisture with PWs as high as 2.7 inches surges over our area on Wednesday, showers and thunderstorms spread from the Coastal Plains early in the morning to the I-35 corridor by midday, then over the Hill Country and the Rio Grande in the afternoon. Recent model trends show the heaviest rains shifting to the south as the Subtropical Ridge begins to build back to the southwest over Texas. However, still expect heavy rains over parts of our area, especially along and south/east of I-10/I-35 where WPC has maintained a Moderate (level 3 out of 4) risk of excessive rainfall and flooding. We have issued a Flood Watch for this area. Have included Bexar county/San Antonio Metro area due to the flashy nature of urban runoff. Expect Watch to be reconfigured going into the long term as this heavy rainfall event evolves. There is a Slight (level 2 out of 4) risk of excessive rainfall and flooding across the remainder of our area. Gusty winds can be expected within the bands of rain. However, any direct wind impacts from the potential tropical cyclone will be well south of our area. Wednesday high temperatures will be well below normal due to the thick clouds and fairly widespread rains. && .LONG TERM... (Wednesday night through Monday) Issued at 204 AM CDT Tue Jun 18 2024 South Central Texas will be in the midst of the expected heavy rain event for the start of the long term period. Wednesday night, showers and thunderstorms will be ongoing across much of the area in an environment with impressive precipitable water values exceeding 2 inches. Breezy easterly to northeasterly wind is expected with gusts to around 30 mph possible, but the main hazard will be the heavy rain and potential for flooding and flash flooding. Highest confidence for the heaviest rain totals remains over the southern half of counties where model guidance, including the most recent runs, have been most bullish. Overnight into Thursday morning, the heaviest precipitation totals should be progressing westward across the area. By Thursday morning, most activity should be located along the Rio Grande. A Flood Watch is currently in effect through 1 PM Thursday while the WPC slight risk for excessive rainfall (level 2 of 4) remains over the western half of the area for Thursday. Rain should become more scattered and light as the day progresses on Thursday, with much lower precipitation chances across the eastern half of the area Thursday night. This will lead to improving conditions to any flooding/flash flooding, although rivers may still be responding and those near any banks that receive decent rainfall upstream should pay attention to the forecast. While generally drier conditions exist Friday through the weekend, some low end precipitation chances remain with more than sufficient moisture in place, mainly over the Coastal Plains. Granted, any rain would be much more isolated/scattered than the round of rain expected Wednesday into Thursday. The cooler temperatures in the upper 70s and 80s on Thursday will increase day by day Friday through early next week. By Sunday or Monday, most locations will be back to near or slightly above normal highs for mid to late June. && .AVIATION... (06Z TAFS) Issued at 1225 AM CDT Tue Jun 18 2024 MVFR CIGs prevail overnight into Tuesday morning, then become SCT-BKN VFR around midday. Some streamer SHRA are expected early to mid morning, however PROBs are low and will keep mention out for now. Will monitor for possible updates to mention. MVFR CIGs return Tuesday evening into night. Higher PROBs for SHRA/TSRA develop in the hours after the current forecast period on Wednesday. Gusty E-SE winds to around 25 KTs can be expected, at times, with sustained E-SE winds around 10 KTs. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 93 75 82 75 / 20 10 70 60 Austin Bergstrom Intl Airport 92 75 81 74 / 20 20 80 60 New Braunfels Muni Airport 94 75 81 75 / 20 20 80 70 Burnet Muni Airport 91 73 81 73 / 10 10 60 70 Del Rio Intl Airport 101 79 93 77 / 0 0 40 80 Georgetown Muni Airport 91 73 81 72 / 10 10 70 60 Hondo Muni Airport 95 75 82 73 / 10 10 70 80 San Marcos Muni Airport 92 73 79 72 / 20 20 80 70 La Grange - Fayette Regional 90 75 79 75 / 30 40 80 40 San Antonio Intl Airport 94 76 81 75 / 20 10 80 70 Stinson Muni Airport 95 77 82 76 / 20 20 80 70 && .EWX WATCHES/WARNINGS/ADVISORIES... Flood Watch from Wednesday morning through Thursday afternoon for Atascosa-Bexar-Caldwell-Comal-De Witt-Fayette-Frio-Gonzales- Guadalupe-Karnes-Lavaca-Medina-Wilson. && $$ Short-Term...04 Long-Term...27 Aviation...04