A weak outflow boundary leftover from showers and thunderstorms that affected portions of extreme Southern Arkansas, East Texas, and Northwest Louisiana during the afternoon and evening of August 8th, lingered near the Interstate 20 corridor of Northwest Louisiana during the morning hours on August 9th. Meanwhile, a closed upper low over Eastern Kansas dove south into Northeast Oklahoma before…
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The episode as NWS SHV wrote it up.
A weak outflow boundary leftover from showers and thunderstorms that affected portions of extreme Southern Arkansas, East Texas, and Northwest Louisiana during the afternoon and evening of August 8th, lingered near the Interstate 20 corridor of Northwest Louisiana during the morning hours on August 9th. Meanwhile, a closed upper low over Eastern Kansas dove south into Northeast Oklahoma before turning more east into Northern Arkansas during the afternoon hours of the 9th. Showers and thunderstorms which developed during the morning over Southeast Oklahoma and Southwest Arkansas reinforced the outflow boundary over extreme Northwest Louisiana, with large scale forcing ahead of the closed low increasing during the afternoon to trigger scattered showers and thunderstorms. One of these storms became strong over Bossier City, with gusty winds peeling a metal roof off of a storage building before weakening during the evening.
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 Shreveport, LA wrote its last area forecast discussion before the first event at Aug 9, 1:12 PM CST, 3 minutes earlier.
Area Forecast Discussion National Weather Service Shreveport LA 212 PM CDT Thu Aug 9 2018 .AVIATION... Isold to sct convection will continue throughout the TAF pd, with impacts to terminals handled on an AMD as necessary basis. Otherwise, cannot rule out some TEMPO MVFR/IFR cigs around sunrise at a few sites, but these will likely not be reflected in the TAF package until later issuances. Expect s to swly winds 5-10 to continue through the remainder of the pd. /12/ && .PREV DISCUSSION... /issued 1050 AM CDT Thu Aug 9 2018/ UPDATE... Convection along I-30 continues to push newd, showing signs of waning in intensity. Latest HRRR run, which seems to be initializing decently, indicates that the convection will continue to diminish/push newd, with only isold to sct development along I-20 later this aftn. Somewhat confident in the very short-term assessment, but far more uncertain as to what will happen this aftn. Have made a few adjustments to PoPs, but overall changes are minor. As for temps, have trended the I-20 corridor and swd upwards from the ongoing fcst, as these areas will likely see very little in aerial rainfall coverage and plenty of sunshine today. /12/ PREV DISCUSSION... /issued 655 AM CDT Thu Aug 9 2018/ AVIATION... An extensive area of convection will continue through at least mid-morning across portions of extreme NE TX/SW AR before diminishing, along the base of an upper level trough that will shift E across AR. MVFR cigs with reduced vsbys will persist while this convection continues, with improvement expected once it diminishes. Farther S, MVFR cigs may develop through mid-morning across portions of Lower E TX and Ncntrl LA before quickly scattering out, with elevated cigs expected to gradually shift ESE across these areas today ahead of this trough. A sct cu field will eventually develop by late morning/midday with heating, with sct convection redeveloping this afternoon over portions of E TX/N LA from the remnants of the morning storms. Confidence remains somewhat low as to the area/timing, and for now, have only inserted VCTS mention for the SHV/MLU terminals only after 20Z, although this convection may develop farther W into E TX, but S of I-20 (and the TYR/GGG terminals). This convection should diminish this evening with the loss of heating, although additional sct redevelopment may occur late tonight over Lower E TX/N LA. WSW winds 5-10kts today, except vrb/gusty in and near the storms, should become light S or Lt/Vrb after 00Z. /15/ PREV DISCUSSION... /issued 428 AM CDT Thu Aug 9 2018/ SHORT TERM.../Today through Friday/ A narrow band of elevated convection has developed this morning generally along the I-30 corridor of NE TX/SW AR, including extreme SE OK, along the base of an upper trough over Ern OK and Ecntrl TX, with a 25-30 SWrly LLJ helping to reinforce an H850 theta-e axis along the areas of heaviest rainfall. Large scale ascent will be reinforced through the morning as a closed low over Ern KS continues to dive S into NE OK, before swinging ESE into Nrn AR this afternoon. Meanwhile, the morning sfc analysis indicates a weak sfc trough (or the remnants of an old outflow bndry from the convection Wednesday) extending along a W to E axis in VC of the I-20 corridor from Ncntrl TX into N LA, with the short term progs suggesting this bndry gradually lifting N to the AR/LA border later this morning. The LLJ should weaken after daybreak this morning and veer wly, with the parent trough axis beginning to pull E as well. Thus, the convection will also weaken with time this morning, although the progs suggest that the convective outflow from the morning convection may help to reinforce the weak sfc trough back Swd this afternoon and help focus sct convection farther S with afternoon heating. Have concentrated likely pops this morning for SE OK/SW AR with mention of heavy rainfall, before tapering pops off back to chance for the afternoon as the sfc trough again helps to focus sct convection over E TX/N LA. Have again trended max temps this afternoon at least a few degrees above the Blends and MOS given the drought conditions and very warm 4" soil temps. Can't also rule out an isolated severe threat mainly this afternoon as the sfc trough interacts with the greater instability near the base of the upper trough axis over portions of E TX/N LA. The short term progs are not very optimistic with more organized and much needed heavier QPF tonight through this weekend even as the base of the trough axis remains stationary in VC of the I-20 corridor of E TX/N LA tonight and Friday, as the parent closed low pulls E away from the Mid MS Valley. Granted, a 20-25kt Srly low level flow may increase tonight and focus enough convergence near the H850-500 trough axis for sct convection to develop, but have kept mid chance pops going over these areas to account for this potential. Drier air aloft looks to entrain SSE around the base of the trough over extreme NE TX/SE OK/SW AR which should taper any nwd development of any organized convection. This trend looks to continue through Friday as well, as the primary troughing begins to exit the region, but having the W to E weakness of the trough around along with the mesoscale bndrys should interact with limited heating for sct convection Friday afternoon. There's a tale of two models as the NAM is much drier Friday than the very wet GFS, which appears likely overdone given the weaker overall forcing than what has been observed this morning. Thus, have split the difference with pops (similar to the ECMWF solution) with mid chance pops again over Lower E TX/N LA along/S of I-20. Near to slightly below normal temps is expected given the considerable elevated cloud cover in VC of the trough. Unfortunately, convection appears to remain hit or miss this weekend as this elevated weakness lingers over the area. 15 LONG TERM.../Friday Night through Wednesday Night/ The weak stationary frontal boundary over the area will continue to diminish and wash out as the NW flow aloft starts to weaken and back to a more Northerly direction. However, the mid level moisture and steep instability will linger and allow for scattered to possible numerous showers and thunderstorms to continue at times this weekend. Overall, the moisture axis lingering over our southern half will begin to shift Northward as the mid level trough continues to move away to our NE. Our daytime highs will continue to be just below average in the lower 90s this weekend and then back to above with mid 90s early next week. This due to the heights aloft building from the South as the Bermuda high noses into E TX/LA during early next work week. Our lows will continue in the lower 70s, slowly rising early to mid 70s by the middle of next week. /24/ && .PRELIMINARY POINT TEMPS/POPS... SHV 97 74 93 74 / 30 40 40 30 MLU 95 72 91 73 / 50 40 50 40 DEQ 88 70 93 70 / 60 20 20 20 TXK 88 73 93 72 / 70 30 30 30 ELD 90 72 92 72 / 50 30 30 30 TYR 98 75 93 73 / 30 40 40 50 GGG 97 75 92 73 / 30 40 40 40 LFK 95 73 90 75 / 30 40 40 30 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...None. LA...None. OK...None. TX...None. && 12/15/24
Hazardous Weather Outlook National Weather Service Shreveport LA 626 AM CDT Thu Aug 9 2018 ARZ050-051-059>061-070>073-LAZ001>006-010>014-017>022-OKZ077- TXZ096-097-108>112-124>126-136>138-149>153-165>167-101130- Sevier-Howard-Little River-Hempstead-Nevada-Miller-Lafayette- Columbia-Union-Caddo-Bossier-Webster-Claiborne-Lincoln-De Soto- Red River-Bienville-Jackson-Ouachita-Sabine-Natchitoches-Winn- Grant-Caldwell-La Salle-McCurtain-Bowie-Franklin-Titus-Camp- Morris-Cass-Wood-Upshur-Marion-Smith-Gregg-Harrison-Cherokee-Rusk- Panola-Nacogdoches-Shelby-Angelina-San Augustine- 626 AM CDT Thu Aug 9 2018 This Hazardous Weather Outlook is for portions of south central Arkansas, southwest Arkansas, north central Louisiana, northwest Louisiana, southeast Oklahoma, east Texas and northeast Texas. .DAY ONE...Today and Tonight... Scattered to numerous thunderstorms will continue along much of the I-30 corridor with some possible flooding in southwest Arkansas this morning. Afternoon heating will bring additional thunderstorm activity along and South of I-20 this afternoon. Any strong thunderstorms could bring locally gusty winds and brief heavy rainfall. During the overnight hours, the chance for thunderstorms may continue beyond sunset with additional development possible along with more soaking rainfall. Meanwhile, our high temperatures will be in the mid 90s along and South of I-20 with this muggy air making our heat index range from 100 to 105 degrees. .DAYS TWO THROUGH SEVEN...Friday through Wednesday... Scattered thunderstorms will be ongoing early on Friday along I-20. As the weak cold front slowly moves into the area and begins to stall out we will see a break from the heat due to added cloud coverage. Scattered to possibly numerous showers and thunderstorms will continue for much of the area off and on this weekend. This thunderstorm activity will begin to become more widely scattered to just isolated by early next week. Locally gusty winds and heavy rainfall will be likely along with minor flooding issues associated with repeated rainfall into the weekend. .SPOTTER INFORMATION STATEMENT... Activation of emergency managers, spotter networks and amateur radio operators could be needed today, as well as possibly during the overnight hours for areas North of I-20. 24
Special Weather Statement
National Weather Service Shreveport LA
205 PM CDT THU AUG 9 2018
LAZ002-003-092000-
Bossier LA-Webster LA-
205 PM CDT THU AUG 9 2018
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHERN WEBSTER AND SOUTHEASTERN
BOSSIER PARISHES UNTIL 300 PM CDT...
At 204 PM CDT, Doppler radar was tracking a strong thunderstorm 7
miles southeast of Bossier City, moving east at 15 mph.
Winds in excess of 40 mph will be possible with this storm.
Locations impacted include...
Bossier City, Minden, Haughton, Sibley, Doyline, Dubberly, Dixie
Inn, Eastwood, Fosters, Princeton, Curtis, Taylortown, Fillmore,
Bodcau, Koran, Barksdale Air Force Base, Gilark, Noles Landing and
Lake Bistineau North.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 3236 9361 3238 9361 3236 9362 3237 9363
3240 9362 3241 9366 3242 9367 3243 9366
3243 9368 3246 9368 3246 9370 3248 9369
3249 9370 3249 9371 3250 9371 3251 9372
3272 9339 3250 9320
TIME...MOT...LOC 1904Z 278DEG 11KT 3242 9359
07The Shreveport radar (KSHV), 18 km away, was scanning. The volume nearest the first event began at 19:14 UTC.
1 thunderstorm wind. Local standard time, as filed.
A metal roof was peeled off of a storage building in Bossier City.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Louisiana in 2018Every state in 2018This day in weather historyWarnings in Louisiana, 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: 767379.