Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX
Issued by NWS Austin/San Antonio, TX
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540 FXUS64 KEWX 220842 AFDEWX Area Forecast Discussion National Weather Service Austin/San Antonio TX 342 AM CDT Sun Sep 22 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (Today through Monday) Issued at 338 AM CDT Sun Sep 22 2024 Low clouds continue to expand in coverage early this morning as noted on the latest GOES Nighttime Microphysics satellite imagery. Upslope flow and low-level moisture will remain in place this morning allowing for a continuation of low clouds. We may even see an isolated shower or two develop across portions of the western Hill Country and southern Edwards Plateau where models show stronger winds around 925mb and 850mb. Otherwise, some light winds and less cloud cover over the coastal plains may allow for some patchy fog development closer to sunrise. For late this afternoon and evening, a cold front will begin to move through west central Texas, with the boundary eventually approaching portions of the western Hill Country and southern Edwards Plateau around sunrise Monday. The hi-res models differ with regards to the amount of convection that develops ahead of and along this front. For now, we will show the higher rain chances during the early morning hours on Monday, mainly for areas north of a Del Rio to Rocksprings line. With the stronger large scale forcing remaining farther to our north, we will keep rain chances capped at 50% for now. For most of our forecast area, suspect the front will not line up with the stronger forcing to our north. The exception could be across the far northern portions of Val Verde and Edwards counties and the SPC does maintain a Marginal Risk for severe storms across these areas. Should any stronger storms manage to develop, gusty outflow winds and hail will be the main severe weather concerns. The leading edge of the front may slip southward into portions of the Hill Country and perhaps even a small portion of the I-35 corridor on Monday. We will maintain a low chance for showers and storms into Monday afternoon for areas generally along and north of an Eagle Pass to Llano line. A few showers and storms may also develop over the coastal plains region during the afternoon hours. As for temperatures, highs remain above normal for all areas today with near 90 in the Hill Country to the mid/upper 90s elsewhere. With the above mentioned cold front expected to drop southward into portions of the Hill Country and southern Edwards Plateau, highs will trend downward into the 80s over these areas. Farther south, not much change in the forecast highs are expected, with perhaps a degree or two drop depending on the amount of cloud cover that lingers into the afternoon hours. Lows tonight will be warm again, with 70s in store for most of the region. && .LONG TERM... (Monday night through Saturday) Issued at 338 AM CDT Sun Sep 22 2024 By Monday evening, the cold front is forecast to be along the Hill Country and the southern Edwards Plateau. The GFS and ECMWF solutions keep the boundary across the Hill Country and southern Edwards Plateau on Monday night into Tuesday while the NAM guidance has the boundary to the south of Interstate 35 stretching from near Georgetown to the southwest into San Antonio and then into Carrizo Springs. It is hard to tell if it dissipates or pushes back to the north as a warm front with winds returning from the southeast. Let`s go with the GFS/ECMWF guidance. Overnight lows are forecast to range from the upper 60s across the Hill Country to mid 70s along the Coastal Plains. The overnight period likely stays rain-free. As the day progresses on Tuesday, temperatures are forecast to go up into the upper 80s across the Hill Country to mid 90s along the Coastal Plains. Mostly cloudy skies are expected to dominate South Central Texas through the period. From this point on (Tuesday afternoon into the evening), the forecast becomes challenging as the NAM solution brings the seabreeze from the Coastal Plains into the I-35 corridor and a surge of northeast winds into the Hill Country. The GFS solution keeps a stationary boundary across the Hill Country with an upper level trough axis pushing across the local area which translates into scattered showers and isolated thunderstorms across most areas of South Central Texas. The unstable weather conditions continue on Wednesday as a stronger cold front pushes through the local area with scattered showers and thunderstorms in addition to cooler temperatures. WPC Day 3 ERO shows the northern part of the Hill Country under a marginal risk for exceeding rainfall amounts. Therefore, a few locations could get a few inches of rainfall but for the most part, half inch and less is expected for most areas based on this forecast package. This is an evolving system. Wednesday`s highs are forecast to range from the lower 80s across the Hill Country to the mid and upper 80s elsewhere. The dry and cooler air mass spreads across the local area Wednesday evening into Thursday with limited to none chances of rain through the period. Overnight lows are forecast to drop to the upper 50s across the Hill Country and within the 60s for the rest of South Central Texas. Dry weather conditions persist the latter part of the work week into the weekend with temperatures running close to the normal climate values (mid to upper 80s for highs/low to upper 60s for lows) for late September. && .AVIATION... (06Z TAFS) Issued at 1251 AM CDT Sun Sep 22 2024 Low clouds continue to expand along the I-35 corridor early this morning and we have started either prevailing or TEMPO groups for MVFR clouds a little ahead of schedule. Low clouds will eventually expand westward to DRT, with MVFR remaining in the forecast here as well. Low clouds will lift and mix back to VFR around 17Z, with VFR expected through this evening. Low cloud development is likely again early Monday morning and will mention SCT low clouds toward the end of our 30 hour sites (SAT and AUS). We could also see some convection develop near or just north of DRT late tonight or early Monday. For now, confidence is on the low side and will not mention in the TAF just yet. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 96 74 94 73 / 0 0 10 10 Austin Bergstrom Intl Airport 95 73 94 73 / 0 0 10 10 New Braunfels Muni Airport 96 73 95 73 / 0 0 10 10 Burnet Muni Airport 93 71 88 69 / 0 20 20 10 Del Rio Intl Airport 96 77 92 75 / 0 30 30 10 Georgetown Muni Airport 94 72 90 71 / 0 10 10 10 Hondo Muni Airport 94 73 93 73 / 0 10 10 10 San Marcos Muni Airport 95 72 94 71 / 0 0 10 10 La Grange - Fayette Regional 94 72 93 72 / 0 0 10 10 San Antonio Intl Airport 95 75 94 75 / 0 0 10 10 Stinson Muni Airport 96 74 95 75 / 0 0 10 10 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term...Platt Long-Term...17 Aviation...Platt