An upper level shortwave trough interacted with a surface stationary front to generate thunderstorms. 5 inches and some of them produced heavy rain that led to flash flooding.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS EWX wrote it up.
An upper level shortwave trough interacted with a surface stationary front to generate thunderstorms. These storms formed in a very moist airmass with PW values above 1.5 inches and some of them produced heavy rain that led to flash flooding.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Austin/San Antonio, TX wrote its last area forecast discussion before the first event at Dec 7, 3:20 PM CST, 1 hour 40 minutes earlier.
Area Forecast Discussion National Weather Service Austin/San Antonio TX 320 PM CST Fri Dec 7 2018 .SHORT TERM (Tonight through Saturday Night)... As expected, widespread rain showers are ongoing across much of the region. Highest rainfall totals so far have been located just east of the Interstate 35 corridor from Marion to just east of Austin. A few LCRA gauges in eastern Travis and western Bastrop County have recorded over 2 inches of rain since midnight. The ASOS at New Braunfels Municipal has recorded 1.82" since midnight with Austin Bergstrom sitting at 1.56" as of 2:10 pm Friday (already a new daily rainfall record). Upper air analysis shows the center of the mid level low currently situated near the California/Arizona border with southwesterly cyclonic flow aloft across South Central Texas. At the surface, the stationary front currently resides from just north of Houston southwest toward Freer and then down toward Zapata. The upper trough will continue its eastward progression, leading to increased PVA and height falls across the region. PWATs ranging from 1.3 inches out west near DRT to 1.7 inches across the Coastal Plains are providing plenty of deep moisture. A 90 knot 300 mb jet streak is also enhancing forcing for ascent. These ingredients will continue to drive the widespread showers and isolated embedded thunderstorms for the remainder of today and into the early overnight period. The heaviest rain should fall between 8 pm and midnight, with the strongest line of showers/thunderstorms expected to reach the I-35 corridor around 10 pm this evening (per convective allowing models). Additional rainfall totals of 0.5 to 2 inches can be expected for most locations west of the Interstate 35 corridor. An additional 2 to 2.5 inches of rain can be expected for the I-35 corridor from Pleasanton up to Georgetown. The eastern portions of the CWA should see an additional 2 to 4 inches of rain. The Flash Flood Watch remains in effect until noon on Saturday. The severe weather threat remains low, with the SPC marginal risk only encapsulating portions of Lavaca, Karnes and DeWitt Counties. The bulk of the accumulating rainfall should exit to the east by early Saturday morning. However, some wrap around moisture on the backside of the upper level low may be enough to produce some sporadic light showers or drizzle into the afternoon hours of Saturday for the northern portions of the CWA. Temperatures on Saturday will be chilly, with highs ranging from the mid 40s across the Hill Country to near 50 for the Austin and San Antonio metro areas, with mid 50s for highs along the Rio Grande. Breezy northerly winds will make it feel much cooler, with wind chills up to 10 degrees colder than actual temperatures. Clouds will begin clearing from west to east by Saturday night, with cloud cover hanging on for areas along and northeast of a Kerrville to San Antonio to Karnes City line. Some areas of the Hill Country may get near freezing early Sunday morning. && .LONG TERM (Sunday through Thursday)... Northwest flow aloft will persist across the region on Sunday as another upper level low pressure system drops southwest into the northern Plains from Canada. Skies should completely clear by Sunday evening for all locations across the region with winds weakening as the surface pressure gradient relaxes. This will allow for strong radiational cooling, likely bringing another freeze to the Hill Country and temperatures near freezing for the rest of the region on Sunday night/Monday morning. Monday will feature high temperatures a few degrees warmer under clear skies, with the northwesterly flow aloft still in place. Another chilly night will be in store for Monday night into Tuesday morning. Upper level ridging begins to build back into the region from the west on Tuesday. Another upper level trough is currently progged to approach the region from the northwest by mid to late next week, leading to southwesterly flow aloft and warm air advection, which will return temperatures back into mid 60s for Wednesday and back to near 70 by Thursday, with moisture levels on the increase. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 44 48 38 52 36 / 100 20 0 0 0 Austin Bergstrom Intl Airport 44 49 39 52 34 / 100 20 0 0 0 New Braunfels Muni Airport 45 50 38 53 33 / 100 20 0 0 0 Burnet Muni Airport 41 44 35 49 31 / 100 30 - 0 0 Del Rio Intl Airport 44 53 38 57 36 / 90 10 0 0 0 Georgetown Muni Airport 42 46 37 50 33 / 100 30 - 0 0 Hondo Muni Airport 46 54 35 57 33 / 100 10 0 0 0 San Marcos Muni Airport 45 50 38 53 34 / 100 20 0 0 0 La Grange - Fayette Regional 46 50 40 52 35 / 100 30 - 0 0 San Antonio Intl Airport 46 51 38 54 36 / 100 20 0 0 0 Stinson Muni Airport 47 53 39 55 36 / 100 20 0 0 0 && .EWX WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Saturday morning for Atascosa-Bastrop- Bexar-Blanco-Burnet-Caldwell-Comal-De Witt-Fayette-Frio-Gonzales- Guadalupe-Hays-Karnes-Kendall-Lavaca-Lee-Medina-Travis-Williamson- Wilson. && Aviation...05 Short-Term/Long-Term...BMW Public Service/Data Collection...YB
Hazardous Weather Outlook National Weather Service Austin/San Antonio TX 323 PM CST Fri Dec 7 2018 TXZ171>173-183>194-202>209-217>225-228-082130- Llano-Burnet-Williamson-Val Verde-Edwards-Real-Kerr-Bandera- Gillespie-Kendall-Blanco-Hays-Travis-Bastrop-Lee-Kinney-Uvalde- Medina-Bexar-Comal-Guadalupe-Caldwell-Fayette-Maverick-Zavala- Frio-Atascosa-Wilson-Karnes-Gonzales-De Witt-Lavaca-Dimmit- 323 PM CST Fri Dec 7 2018 This Hazardous Weather Outlook is for South-Central Texas.. .DAY ONE...This Afternoon And Tonight. A cold front and potent upper level disturbance will continue to bring widespread showers and a chance of thunderstorms to the area through late tonight. Locally heavy rainfall will be possible, potentially leading to flooding. Up to 2 inches of rain has already fallen across portions of South Central Texas. Additional rainfall totals of 0.5 to 2 inches can be expected for most locations west of the Interstate 35 corridor. An additional 2 to 2.5 inches of rain can be expected for the I-35 corridor from Pleasanton up to Georgetown. The eastern portions of the CWA should see an additional 2 to 4 inches of rain. A Flash Flood Watch has been issued for these areas, in effect from Friday afternoon through Saturday morning. Flooding of creeks, smaller tributaries, low water crossings, and urban areas that are normally subject to flooding will be possible. In addition, there is a marginal risk some storms across far southeastern areas could become strong to severe Friday afternoon and evening. .DAYS TWO THROUGH SEVEN...Saturday through Thursday. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to report rainfall measurements.
The Austin/San Antonio radar (KEWX), 24 km away, was scanning. The volume nearest the first event began at 23:02 UTC.
3 flash flood. Local standard time, as filed.
Thunderstorms produced heavy rain that led to flash flooding sending Morrison Creek over SE River Rd. outside Martindale. Two people were killed when their vehicle was swept into the flood waters.
Thunderstorms produced heavy rain that led to flash flooding covering Knobbs Rd. with 1.5 feet of water northeast of McDade.
Thunderstorms produced heavy rain that led to flash flooding when Cottonwood Creek left its banks and covered Old Kimbro Rd. east of Manor. Two people were rescued from the top of their car when it stalled in the flood waters.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
| Event | Date | Age | Sex | Where | Kind |
|---|---|---|---|---|---|
| Flash Flood, Caldwell | 2018-12-07 | 62 | Female | Vehicle/Towed Trailer | Direct |
| Flash Flood, Caldwell | 2018-12-07 | 63 | Male | Vehicle/Towed Trailer | Direct |
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Texas in 2018Every state in 2018This day in weather historyWarnings in Texas, December 2018
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 796017, 796018, 796019.