613 FXUS64 KEWX 091137 AFDEWX Area Forecast Discussion National Weather Service Austin/San Antonio TX 637 AM CDT Sat Oct 9 2021 .AVIATION... VFR conditions will continue through the morning and into the day today. Some brief patchy fog has formed along the Coastal Plains, but indications are that this will stay just to the east of the terminals through the morning hours. Winds will pick up out of the south this afternoon between 08 and 14 knots, and be gusty at times at DRT. With plenty of Gulf moisture returning to the area think at least MVFR ceilings are possible in most areas tomorrow morning beginning some time between 06z and 09z. Models are indicting IFR at the San Antonio terminals, but not confident enough yet to prevail IFR. For now included a SCT007 for SAT/SSF. Some indications are that the MVFR will make it all the way out to DRT by daybreak on Sunday as well. With winds becoming elevated not super confident in this so have only mentioned a SCT025 at DRT for Sunday AM. && .PREV DISCUSSION... /ISSUED 256 AM CDT Sat Oct 9 2021/ SHORT TERM (Today through Sunday)... Enjoy the warm and sunny weekend because big changes are on the way starting Sunday night and continuing for the middle to late part of next week as a pair of cold front arrive. In the short term though the upper level ridge will maintain its grasp on South Central Texas today before being forced south as a potent upper level trough arrives late Sunday afternoon into Sunday night. While the main impacts from the trough will be felt starting Sunday night (in the long term period) the trough will be approaching the Texas Panhandle by Sunday afternoon. At the surface the ridge to the east will continue to produce southerly winds across the area hastening the return of Gulf of Mexico moisture. This will result in the return of morning low clouds for Sunday. As the surface low pressure develops over north Texas late Sunday the pressure gradient ahead of it will tighten with the high to the east producing some gusty southerly winds during the afternoon hours. Temperatures will also be on the increase with the increasing moisture. Today will be another day in the lower 90s, but tonight rather than lows in the low to mid 60s (as we are seeing tonight), forecasted lows are roughly 5 to 8 degrees warmer in the mid to upper 60s. Highs on Sunday will also follow this trend topping out in the low to mid 90s. Highs may even be a few degrees warmer depending on the progress of the front and compressional warming ahead of it. By late Sunday afternoon dew points will be in the 70s and the strong upper trough will be moving into North Texas. This will prime the atmosphere for the arrival of the front Sunday night. LONG TERM (Sunday Night through Friday)... Strong agreement in the model guidance with the placement of the H5 trough axis over the TX Panhandle to begin the long term. Sunday evening, the breezy southerlies will begin to subside ahead of the arrival of a cold front associated with the system. The front will begin to move in from the NW right at the start of the period, but model soundings indicate CIN that will gradually erode away in the 00Z-06Z time period. Showers and storms should develop as the cap breaks, likely entering our Hill Country counties around 10pm give or take 1-2 hours, then spreading south and east through the overnight then exiting the Coastal Plains after sunrise Monday morning. Even after midnight, CAPE values are forecast to exceed 1500J/kg and deep layer shear, though more impressive well to our north, will be sufficient for organized, potentially rotating storms. A storm or two will have the potential to become severe with large hail and/or damaging winds possible, with the new SPC Day 2 outlook expanding the Marginal Risk area to include locations north of Utopia to New Braunfels to La Grange. Precipitation amounts won't be too impressive, with most areas seeing less than half an inch but locally higher amounts up to 2" cannot be ruled out. Per NAM, which typically handles cold fronts well, we could be in for a cooler day Monday behind the front than is currently forecast and so I've hedged in that direction from the still relatively warm NBM. However, even if the cold front does clear south-central TX, it'll turn right back around as a warm front and pass back to our north Monday night. Could be some isolated streamer shower activity in the warm sector but have left mention out of the forecast for now. Tuesday will be warm, humid, and a bit breezy once again with southerly winds gusting to 25 and potentially 30 mph at times. The next trough, much deeper than the first, will be located near the Four Corners at 18Z Tuesday. It's progression appears slightly slower than the last few model runs, but confidence is beginning to increase in it's track as it deepens and turns to the NE and eventually N, passing over the Dakotas on Wednesday and Wednesday night. Here in TX, some isentropic lift in the warm sector could lead to precipitation development over the Rio Grande Plains early Wednesday, but chances for showers and storms will increase and spread east through the day, continuing through the end of the period as the frontal boundary becomes nearly stationary. With southeasterly flow in the BL tapping into gulf moisture and SW flow aloft bringing additional moisture from the Pacific coincident with a likely EPAC tropical system coming onshore somewhere over MX, confidence continues to increase in very anomalous PW potentially as high as 2.3". Ensemble mean values have increased run to run and now exceed 2" for parts of the area Wednesday night, and in combination with low level convergence along the front, divergence in the RER of a SW/NE oriented jet aloft, and PVA ahead of a secondary trough axis, periods of showers and thunderstorms will be likely and locally heavy rainfall could be a concern in the Wed-Fri period. Details of timing and placement of the greatest risk will continue to be refined over the coming days. Operational GFS remains more bullish on moisture and forcing than most guidance and impacts are still not a guarantee with many ensemble members still outputting manageable, drier solutions. Will keep POPs capped at 50 through the period until things become clearer. Ridging will build into the western US as we head into next weekend, finally allowing the pattern to become more progressive and pushing the frontal boundary through the region Friday night or Saturday. We should see conditions dry out behind it over the weekend and cooler air should finally move in with highs likely in the 70s. PREV DISCUSSION... /ISSUED 1234 AM CDT Sat Oct 9 2021/ AVIATION... Another night of VFR conditions is expected tonight through tomorrow as southerly winds continue across the I-35 terminals with southeasterly winds at DRT. Moisture continues to stream into the area with southerly winds picking up between 10 and 14 knots tomorrow at all TAF sites. This will allow for overnight stratus to return for Sunday morning. While future TAF packages will nail down the timing and the height of the ceilings, have gone ahead and introduced low end MVFR at the two 30 hour TAF sites for Sunday morning. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 90 70 92 69 86 / 0 - - 60 - Austin Bergstrom Intl Airport 89 68 92 69 86 / 0 - - 60 - New Braunfels Muni Airport 89 68 93 70 86 / 0 - 0 50 - Burnet Muni Airport 89 67 90 63 84 / 0 - 0 50 - Del Rio Intl Airport 93 69 95 66 91 / 0 0 0 10 0 Georgetown Muni Airport 90 69 91 65 85 / 0 0 - 50 - Hondo Muni Airport 91 68 95 69 89 / 0 - 0 30 - San Marcos Muni Airport 89 68 93 69 86 / 0 - - 50 - La Grange - Fayette Regional 90 70 91 72 86 / 0 - 10 60 20 San Antonio Intl Airport 90 71 93 72 87 / 0 - - 40 - Stinson Muni Airport 91 71 95 73 88 / 0 0 0 30 - && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term/Aviation...Treadway Long-Term...KCW