A line of showers and storms produced a downburst in south central Oklahoma on the afternoon of the 13th on their way southeast.
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The episode as NWS OUN wrote it up.
A line of showers and storms produced a downburst in south central Oklahoma on the afternoon of the 13th on their way southeast.
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 Norman, OK wrote its last area forecast discussion before the first event at Aug 13, 11:47 AM CST, 1 hour 3 minutes earlier.
Area Forecast Discussion...UPDATED National Weather Service Norman OK 1247 PM CDT Mon Aug 13 2018 .AVIATION... 13/18Z TAFs. MVFR/IFR conditions will dominate the forecast for most terminals, with VFR conditions possible across far western Oklahoma this afternoon and evening. Large area of rain will continue to progress north and east over region through tonight. TSRA expected to increase this afternoon but stay south and east of KSPS/KOUN/KOKC terminals. IFR stratus and fog will be possible tonight and Tuesday morning from KSPS up through KOKC/KPNC. && .PREV DISCUSSION... /issued 1038 AM CDT Mon Aug 13 2018/ UPDATE... Increased pops, essentially to a large area of categorical/100 pops as moist conveyor streams northeast ahead of upper low. Also increased rainfall amounts given tropical nature of precipitation. PREV DISCUSSION... /issued 558 AM CDT Mon Aug 13 2018/ DISCUSSION... AVIATION... Rain will increase and move south to north across much of central and eastern Oklahoma today. MVFR conditions will exist at times with low ceilings in stronger showers. PREV DISCUSSION... /issued 320 AM CDT Mon Aug 13 2018/ DISCUSSION... We're anticipating expanding coverage of convection early this morning as an upper jet max and attendant forcing for ascent move into western Oklahoma. This is clearly seen in moisture channel imagery moving into the Texas Panhandle now. Mass response/strengthening low-level jet is already beginning to force convection along the I-20 corridor to our south in Texas. Lighter showers are increasing in coverage further north along the Red River. We have high (categorical) precipitation probabilities for a good portion of southern and central Oklahoma this morning. Locally heavy rainfall is expected given the moist environment. 00 UTC KOUN sounding sampled 2.05" precipitable water, and 00 UTC KFWD sounding sampled 2.16" PW. Models show 12-14 KFT warm cloud depth which further supports efficient precipitation rates with any convection that occurs this morning. There are a couple limiting factors for a more robust heavy rain/flooding event. Often our more significant flooding/flash flooding events occur in higher instability environments with training/backbuilding intense deep convection. Instability will be limited, typical of meridional flow with weak mid-level lapse rates. Thus, convection will not be very intense, and in fact we've limited thunder to "chance" or "slight chance", despite "likely" or "categorical" precipitation. We also re-introduced mention of heavy rain, mainly for south-central and southeast portions of the area. This places emphasis on intermittent showers with locally heavy rainfall amounts which seems to more appropriately fit this scenario. After a conversation with surrounding offices, we decided not to issue a Flood Watch right now, but left the option open for later this morning depending on trends. The biggest limitation that kept us from issuing now was uncertainty on placement of heavy-rain producing convection. Spatial discrepancies between SSEO members, TTU-WRF, ARW, NAM, etc., lower confidence. We felt the best strategy would be to watch this evolve some and if we need to issue a Flood Watch we could be more specific with where, rather than broad brushing and having a large false alarm issue. We'll monitor trends this morning and issue a watch more on the time scale that SPC typically issues convective watches if it becomes apparent that a particular area stands a good chance of seeing flooding/flash flooding. It seems now that one vulnerability may be where Flash Flood Guidance is locally relatively low in the terrain of the Arbuckles across south-central Oklahoma, and the eastward into southeast Oklahoma also. This is the area we'll need to watch closely this morning and probably into tonight as well, as multiple rounds of heavy precipitation could occur. Closed low will continue to deepen more and move slowly northeast into Kansas through Tuesday. Occasional vort maxima enhancing DPVA will force rounds of convection through Tuesday night. These are a little difficult to time out, but as of now it appears we'll see an initial one through at least the first half of today, followed by another later tonight, and a final late Tuesday. For the late Tuesday round, we'll have more veered flow, steeper lapse rates, and slightly stronger mid-level flow suggesting a few storms that form along the front could be strong to severe. Although instability/shear will be quite marginal then, it's better than the previous days. Heavy rainfall amounts may still be a concern with Tuesday afternoon/night convection. Wednesday should be dry for most as mid-level heights rise in the wake of the departing low. We'll then return to a potentially wet pattern with periodic shower/storm chances late week through the weekend. Mean flow will be northwesterly and perturbations within the flow could bring a few rounds of precip. Timing will be better refined in later forecasts. BRB && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 76 68 84 70 / 100 60 40 60 Hobart OK 79 69 88 70 / 80 30 30 40 Wichita Falls TX 78 71 91 73 / 100 50 30 20 Gage OK 82 66 83 64 / 50 40 50 20 Ponca City OK 78 69 83 69 / 100 70 60 70 Durant OK 79 69 84 73 / 80 80 50 30 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && 11/06
Hazardous Weather Outlook National Weather Service Norman OK 1200 PM CDT Mon Aug 13 2018 OKZ004>048-050>052-TXZ083>090-141045- Harper-Woods-Alfalfa-Grant-Kay-Ellis-Woodward-Major-Garfield- Noble-Roger Mills-Dewey-Custer-Blaine-Kingfisher-Logan-Payne- Beckham-Washita-Caddo-Canadian-Oklahoma-Lincoln-Grady-McClain- Cleveland-Pottawatomie-Seminole-Hughes-Harmon-Greer-Kiowa-Jackson- Tillman-Comanche-Stephens-Garvin-Murray-Pontotoc-Coal-Cotton- Jefferson-Carter-Johnston-Atoka-Love-Marshall-Bryan-Hardeman- Foard-Wilbarger-Wichita-Knox-Baylor-Archer-Clay- 1200 PM CDT Mon Aug 13 2018 This hazardous weather outlook is for portions of northern... western...central...and southern Oklahoma...and western north Texas. .DAY ONE...Through Tonight... .Thunderstorms... Thunderstorms will be possible this afternoon and tonight, especially across south central and southeast Oklahoma this afternoon. A few thunderstorms may produce strong damaging winds. Lightning and heavy rain can be expected too. .Heavy Rainfall and Flooding... Locations that experience multiple heavy rain-producing storms could experience flooding. The most likely area for heavy rain and flooding this afternoon and evening will be across south central and southeastern Oklahoma. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday... .Thunderstorms... Thunderstorms will be possible each day through the upcoming weekend, although the greatest chance will be Tuesday. A few strong to severe storms are possible Tuesday afternoon and evening, but widespread or significant severe weather is not expected. .Heavy Rainfall and Flooding... A very moist environment could support heavy rainfall rates with storms that occur Tuesday and Tuesday night. Localized flooding is possible. Get graphics and more details at weather.gov/norman...and follow our weather forecast office on Twitter and Facebook.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
927 AM CDT MON AUG 13 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0417 PM TSTM WND DMG 7 S SAYRE 35.20N 99.63W
08/10/2018 BECKHAM OK EMERGENCY MNGR
TWO STRUCTURES RECEIVED ROOF DAMAGE WITH SHINGLES BLOWN
OFF. PIVOT IRRIGATION SYSTEM BLOWN OVER. SEVERAL TREE
LIMBS UP TO SIX INCHES IN DIAMETER SNAPPED OFF TREES.
&&
FMSPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE Norman OK
147 PM CDT MON AUG 13 2018
OKZ040-041-046-131915-
Carter OK-Garvin OK-Murray OK-
147 PM CDT MON AUG 13 2018
...SIGNIFICANT WEATHER ADVISORY FOR east central Carter...
southeastern Garvin and Murray Counties Until 215 PM CDT....
AT 144 PM CDT, a strong thunderstorm was located near Springer,
moving northeast at 20 MPH.
HAZARDS INCLUDE...
Wind gusts to 50 MPH...
Minor flooding in areas of poor drainage...
Heavy rain can lead to reduced visibility...
Locations impacted include...
Sulphur, Davis, Wynnewood, Springer, Dougherty, Hickory, Scullin,
Lake Of The Arbuckles and Turner Falls.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Severe weather is not expected and no warnings are anticipated at
this time.
Conditions are favorable for the formation of funnel clouds, but the
threat posed by these funnel clouds is low. Most funnel clouds will
not reach the ground. If they do, weak tornadoes with brief wind
gusts in excess of 50 MPH may occur.
If you observe a funnel cloud or one is reported in your area, move
indoors and stay away from windows.
&&
LAT...LON 3437 9730 3468 9716 3455 9683 3454 9683
3451 9686 3450 9688 3449 9688 3427 9710
TIME...MOT...LOC 1844Z 216DEG 17KT 3432 9719
11The Norman radar (KTLX), 146 km away, was scanning. The volume nearest the first event began at 18:50 UTC.
1 thunderstorm wind. Local standard time, as filed.
Possible downburst knocked 2 mobile homes off their foundations and scattered them approximately 5 feet. Time estimated from radar.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oklahoma in 2018Every state in 2018This day in weather historyWarnings in Oklahoma, August 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: 781596.