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FXUS64 KEWX 182341 AFDEWX

Area Forecast Discussion National Weather Service Austin/San Antonio TX 641 PM CDT Sat May 18 2024

New AVIATION

SHORT TERM
(Tonight through Sunday night)
Issued at 112 PM CDT Sat May 18 2024

Zonal flow to slight ridging prevails aloft and as a result the short-term forecast period will be mostly quiet. Morning fog has given way to clear skies across all of South-Central Texas early this afternoon. These mostly clear skies should prevail for the remainder of the day for much of the area outside a few clouds possible in the Coastal Plains later today with peak heating. High temperatures today will be near 90 in the northeast up into the 100- 104 degree range in the Rio Grande Plains. Some return of low clouds and patchy fog can be expected tonight for mainly the eastern areas with lows in the upper 60s to middle 70s. Mostly clear skies will then return by the early afternoon with high temperatures similar to today. Surface winds may be a bit more breezy out west and could create some elevated fire weather conditions mainly for the Edwards Plateau. Lows will be back in the upper 60s to middle 70s for most locations across the area tomorrow night.

LONG TERM
(Monday through Saturday)
Issued at 112 PM CDT Sat May 18 2024

There's really no other way to put it than it's going to be hot for at least the next week plus as 500mb ridging builds in over northern Mexico. One caveat: we will be on the northern periphery of this strengthening ridge, so by the middle to end of the upcoming week, the door may be opened to some northwesterly flow aloft within the large scale pattern which could bring some rain and storm chances back into the picture. The CPC places most of the region in a 70-80% chance for above normal temperatures through the 6-10 period which goes out through late May.

Taking a look at GFS/ECMWF ESAT tables indicates 500mb temperatures will be within the 97th to 99th percentile Monday afternoon through Tuesday afternoon, and 700mb temperatures will be equally anomalous if not even more significant for mid to late May, as starting Tuesday afternoon and continuing through Wednesday afternoon, they'll be within the 99th percentile to climatological maximum for mid-late May. Another item to note is the dry soils over the western CWA, particularly the Rio Grande Plains and Southern Edwards Plateau, where NASA SPoRT LIS 0-100cm soil moisture is between 10 and 30% compared to the very wet soils over portions of the Coastal Plains and the northern I-35 Corridor between San Marcos and northern Williamson County. Have opted to lean more towards the NBM 25th/50th percentile for Max T's over the eastern CWA to account for the wetter soils. It'll still be very hot, and in fact, the newest NWS product available for the entire CONUS as of earlier this month, HeatRisk, highlights a good chunk of our area within the Moderate to Major categories Tuesday-Thursday, with Wednesday and Thursday exhibiting Extreme risk for portions of the Rio Grande Plains and Winter Garden Region into Dimmit, Zavala, and Maverick Counties.
Most of this is likely due to the early season nature of this heatwave and folks not being acclimated quite yet. Tuesday and Wednesday will likely flirt with heat indices in the 105-115 range over the Rio Grande Plains, with some 100-105 range heat indices over the I-35 Corridor and Coastal Plains. That risk for higher heat indices may increase even further by late week, where Thursday and Friday could potentially result in heat products for the I-35 Corridor, Rio Grande Plains, and Coastal Plains. Record highs look like a good bet at Del Rio, but at the other sites, we'll likely remain just below record highs through the week.

Last, but not least, as mentioned above, we could transition into more of a northwest flow pattern by late week into next weekend, with rain and storm chances developing over the Hill Country and spreading southeastward into the I-35 Corridor each day. For now, the main focus will be on this early season heatwave.

AVIATION
(00Z TAFS)
Issued at 635 PM CDT Sat May 18 2024

Mostly clear skies and light SE winds are expected for the first 9 hours of all TAF sites. After 09Z some patchy fog and low clouds could develop over the I-35 terminals, but the most layer is expected to be too shallow for impacting DRT. IFR cigs and possible VSBYs could carry over into the mid morning hours, but most areas should mix out to VFR by around noon. A few gusts to 20 knots may occur Sunday afternoon so an extra period of wind direction trend changes were added to the back end of the TAFs.

PRELIMINARY POINT TEMPS/POPS
Austin Camp Mabry 71 92 72 91 / 0 0 0 0 Austin Bergstrom Intl Airport 70 90 70 92 / 0 0 0 0 New Braunfels Muni Airport 70 93 71 94 / 0 0 0 0 Burnet Muni Airport 70 90 70 89 / 0 0 0 0 Del Rio Intl Airport 76 105 76 106 / 0 0 0 0 Georgetown Muni Airport 70 89 70 89 / 0 0 0 0 Hondo Muni Airport 70 96 71 98 / 0 0 0 0 San Marcos Muni Airport 69 92 70 93 / 0 0 0 0 La Grange - Fayette Regional 71 90 72 89 / 0 0 0 0 San Antonio Intl Airport 71 93 73 95 / 0 0 0 0 Stinson Muni Airport 72 94 74 96 / 0 0 0 0

EWX WATCHES/WARNINGS/ADVISORIES
None.

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