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FXUS64 KEWX 111119 AFDEWX

Area Forecast Discussion National Weather Service Austin/San Antonio TX 619 AM CDT Sat May 11 2024

New AVIATION

SHORT TERM
(Today through Sunday)
Issued at 215 AM CDT Sat May 11 2024

A closed low is located just west of the Four Corners region this morning with subtle southwesterly flow over South Central Texas.
This upper low shifts eastward through the day, moving over the Central Plains on Sunday. This feature and some weak ascent ahead of it will lead to precipitation chances today through the weekend. For today, rain chances remain on the low side through the morning, although a light shower cannot be ruled out in the west. The better chances come this afternoon and evening and continue through Sunday supported by the advancing upper level shortwave. Any storms this afternoon would likely be elevated and there remains a low end potential for a strong to severe storm in the western half of the area with hail and damaging wind the main threat. If any storms form in Mexico and move across the Rio Grande this evening, an isolated tornado threat would also be possible. Precipitation chances continue overnight mainly in the 40 to 50 percent range with better chances shifting to the eastern half of the area for Sunday. A low chance for strong to severe storms continues this day. Storms this weekend may also produce heavy rain at times leading to isolated flooding, especially if falling over locations that have seen rainfall in previous days.

Highs will range from the upper 70s and low 80s today across the northeastern half of the area to the mid to upper 80s over the Rio Grande Plains and along the Rio Grande. Cloud cover will thicken and lower overnight with lows in the mid 60s to low 70s. Sunday may be a few degrees warmer than today in some locations, with highs generally in the 80s to mid 90s.

LONG TERM
(Sunday night through Friday)
Issued at 215 AM CDT Sat May 11 2024

Ongoing showers and perhaps a few thunderstorms will be possible Sunday night as an 500mb low over central Kansas passes to our north.
On Monday, a shortwave looks to round the base of the passing 500mb low, resulting in another round of showers and storms by the afternoon. Additionally, a weak frontal boundary should slide through our region Monday afternoon and evening, providing a surface focus for convection to develop along as it moves south and east. The latest global guidance from the GFS/ECMWF hints at a threat for some strong to severe storms Monday afternoon and evening as this front moves through. Deep layer shear of 40-50 kts, and MLCAPE of 1500-2000 J/kg shouldn't be hard to come by, by MLCIN may be a bit on the high side, so a cap may be in place. With a boundary to focus convection on and a shortwave disturbance to work with, a threat for large hail and damaging wind may materialize Monday afternoon and evening over the Hill Country, I-35 Corridor, and the Coastal Plains. SPC places the I-35 Corridor and points eastward within a level 2 of 5 risk for severe storms Monday afternoon and evening.

After the front has passed, we may see a brief break from the humidity on Tuesday as afternoon dewpoints fall into the 60s rather than 70s like we will experience Monday afternoon/evening ahead of the frontal boundary. Afternoon highs may be a tad cooler, but the main difference will be lower humidity. Highs should top out in the upper 80s to mid 90s from east to west. Shortwave ridging at the 500mb level should result in a dry forecast Tuesday.

On Wednesday, yet another round of showers and thunderstorms looks like a good bet, particularly out west over the Rio Grande Plains and Southern Edwards Plateau. A broad 500mb trough over the Four Corners will eject out over the Southern Plains states, resulting in strong southerly surface flow and increasing instability and deep layer shear. Storms look to develop over the western zones and spread eastward by Wednesday night into early Thursday before clearing the region. For now, there is no extended period severe outlook from SPC, but the risk exists at this distance as model guidance has come into better agreement over the last couple days.

Once storms exit the region Thursday morning, we should see hot and dry weather return as 500mb ridging attempts to build in from northern Mexico in the 6-8 day time frame.

AVIATION
(12Z TAFS)
Issued at 619 AM CDT Sat May 11 2024

VFR conditions continue through much of the day at I-35 sites, with near MVFR conditions expected at DRT through the morning. MVFR ceilings fill back in over South Central Texas around or slightly after 00Z Sunday. Ceilings will lower to IFR as early as 04Z with local LIFR conditions possible near sunrise. Precipitation will likely hold off at sites this morning with increasing chances beginning mid afternoon and continuing into Sunday. Exact timing for any potential precipitation is still difficult to pinpoint but used hi-res guidance to estimate the onset on showers and thunderstorms.
Timing will likely be modified in future forecasts.

PRELIMINARY POINT TEMPS/POPS
Austin Camp Mabry 83 65 82 73 / 20 50 80 30 Austin Bergstrom Intl Airport 83 66 83 72 / 20 50 80 40 New Braunfels Muni Airport 83 66 83 73 / 20 50 70 30 Burnet Muni Airport 79 65 79 71 / 20 50 80 30 Del Rio Intl Airport 86 72 91 74 / 30 50 20 20 Georgetown Muni Airport 82 65 79 71 / 20 40 90 30 Hondo Muni Airport 85 68 86 73 / 20 50 40 30 San Marcos Muni Airport 82 65 83 72 / 20 50 80 30 La Grange - Fayette Regional 82 68 85 74 / 20 30 80 40 San Antonio Intl Airport 83 67 85 74 / 20 50 60 30 Stinson Muni Airport 84 69 86 75 / 20 50 50 30

EWX WATCHES/WARNINGS/ADVISORIES
None.

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