A very moist air mass interacted with a passing upper disturbance. High rainfall rates and slow storm motion allowed flash flooding to occur.
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The episode as NWS LCH wrote it up.
A very moist air mass interacted with a passing upper disturbance. High rainfall rates and slow storm motion allowed flash flooding to occur.
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 Lake Charles, LA wrote its last area forecast discussion before the first event at Sep 28, 5:04 AM CST, 1 hour 33 minutes earlier.
Area Forecast Discussion National Weather Service Lake Charles LA 604 AM CDT Tue Sep 28 2021 .DISCUSSION... For 09/28/2021 12Z TAF Issuance. && .AVIATION... Radar showing numerous showers and embedded thunderstorms lifting through the region this morning. Aside from the convection, had already seen CIGS mostly in the MVFR to IFR range, with some lowered VIS in spots as well. Within the convection, expect the addition of some gusty winds with lowered CIGS/VIS. Guidance suggests activity will continue to develop and lift NNE over the next several hours. Included TEMPO groupings with the exception of BPT, where so far development has been skirting the terminal. Subsequent TEMPO groupings may be needed, but this mornings convection should help stabilize the atmosphere some, allowing for maybe a little less activity this afternoon. With that, opted to just keep VCTS mention for the afternoon hours. Outside of convection, CIGS should improve to VFR through the day. By late evening into the overnight hours, CIGS once again begin to lower. Rain chances remain low for the first half of the night, but will pick back up closer to daybreak. In addition, looking at the potential for some patchy BR development after midnight. 50/SW && .PREV DISCUSSION... /issued 328 AM CDT Tue Sep 28 2021/ DISCUSSION... SHORT TERM [Today through Thursday Night]... Muggy summerlike conditions this morning with dew points and temperatures largely in the mid to upper 70s. Aside from that, a broken stratus deck has formed over a large chunk of the region, and areal observations show deteriorated visibility and localized patchy fog in spots. With light winds and ample moisture, could see the fog expand a bit more prior to daybreak. Radar is also showing thundershowers in the coastal waters lifting northward currently, as well as some nocturnal showers developing inland. As upper difluence increases due to an approaching southern stream jet streak, expect to see increasing development close to daybreak and onward through the morning hours. 00Z HREF guidance shows good agreement in this occurring, with the recent 06Z HRRR guidance also quite bullish on a marked uptick in activity. With modest instability and warm cloud depths, a few stronger storms will be capable of efficient rainfall production. Given slow storm motion vectors and the possibility of backbuilding and/or repeat storms, there will at be some threat for localized flooding. HREF LPMM QPF shows some localized maxima of around 2-4+" or so, roughly along/south of the I-10 corridor in far SW LA into SE TX. To that extent, the area has been included in a Marginal Risk of Excessive rainfall (level 1 out of 4) for the day. With activity expected to flare up on the early side today, it should help begin to stabilize the environment thereafter, and guidance suggests convection should begin to taper off some by mid-afternoon and into the evening hours. This relative lull then is expected to continue holding into early Wednesday morning. With light winds and plenty of moisture, once again will be looking at the potential for some areas of patchy fog development as well. One thing to monitor is an MCS like feature some high resolution CAMS develop in central TX overnight which then propagates eastward. Bulk of guidance suggests it should fizzle by the time it reaches E TX, but not a total certainty. Regardless of the potential MCS, jet divergence/difluence further increases as jet streak noses further east, and new convection is likely to fire close to dawn once more. Like today, environment will be supportive of efficient rainfall and slow storm movement, so could deal with a localized flooding threat again. By Thursday, the W CONUS trough amplifies and southern stream jet remains supportive of at least one more day of elevated precip potential. With the fairly high rain chances, expecting daily high temps near to a bit below average in the short term, with morning lows above average. 50/SW LONG TERM [Friday through Tuesday]... The upper air pattern Friday shows a mid to upper level trough over the Western U.S. lifting northeast across the Midwest. By the weekend, the upper air pattern will become more zonal across the Southern U.S. as a large dominate upper level low over the Northern Plains prevails through Monday. The upper air pattern will periodically send perturbations, providing sufficient lift with the available Gulf moisture, to keep intermittent periods of isolated to scattered showers and thunderstorms for Friday and Saturday. Lower chances of precipitation is possible by Sunday and Monday. A weak cool front may move through on Monday, bringing slightly lower temperatures. However, the prevailing upper air pattern will provide more uncertainty in the extended forecast. DML MARINE... Light to moderate onshore winds will prevail through the week. A series of upper disturbances passing over Texas will keep scattered to at times widespread showers and storms over the coastal waters through much of this week. && .PRELIMINARY POINT TEMPS/POPS... AEX 85 71 84 69 / 50 40 80 30 LCH 83 72 84 72 / 70 60 70 60 LFT 85 72 84 71 / 60 50 80 40 BPT 85 72 83 71 / 60 70 70 60 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...None. TX...None. GM...None. &&
Hazardous Weather Outlook National Weather Service Lake Charles LA 334 AM CDT Tue Sep 28 2021 LAZ027>033-041>045-052>055-073-074-TXZ180-201-215-216-259>262-290845- Vernon-Rapides-Avoyelles-Beauregard-Allen-Evangeline-St. Landry- Calcasieu-Jefferson Davis-Acadia-Lafayette-Upper St. Martin- Vermilion-Iberia-St. Mary-Lower St. Martin-West Cameron-East Cameron- Tyler-Hardin-Jefferson-Orange-Northern Jasper-Northern Newton- Southern Jasper-Southern Newton- 334 AM CDT Tue Sep 28 2021 This Hazardous Weather Outlook is for central Louisiana, south central Louisiana, southwest Louisiana, west central Louisiana and southeast Texas. .DAY ONE...Today and tonight. Showers and thunderstorms increase in coverage this morning, becoming fairly numerous through early afternoon. A few storms may be strong and capable of producing heavy rainfall, so a localized flash flood threat can't be ruled out. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. An upper level trof will interact with gulf moisture across the region to produce widespread showers and thunderstorms Wednesday through the end of the week. A few of these storms may be marginally strong and capable of producing locally heavy rainfall. Widespread hazardous weather is not expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. GMZ430-432-435-450-452-455-470-472-475-290845- Sabine Lake-Calcasieu Lake-Vermilion Bay- Coastal waters from Cameron LA to High Island TX out 20 NM- Coastal waters from Intracoastal City to Cameron LA out 20 NM- Coastal waters from Lower Atchafalaya River to Intracoastal City LA out 20 NM-Waters from Cameron LA to High Island TX from 20 to 60 NM- Waters from Intracoastal City to Cameron LA from 20 to 60 NM- Waters from Lower Atchafalaya River to Intracoastal City LA from 20 to 60 NM- 334 AM CDT Tue Sep 28 2021 This Hazardous Weather Outlook is for the Gulf of Mexico and the coastal lakes and bays of the Gulf of Mexico. .DAY ONE...Today and tonight. Showers and thunderstorms increase in coverage this morning, becoming fairly numerous through early afternoon. A few storms may be capable of gusty winds and frequent cloud to water lightning. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. An upper level trof will interact with gulf moisture across the region to produce widespread showers and thunderstorms Wednesday through the end of the week. A few of these storms may be marginally strong. Widespread hazardous weather is not expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
Special Weather Statement
National Weather Service Lake Charles LA
629 AM CDT Tue Sep 28 2021
LAZ027-028-030-031-281230-
Allen LA-Beauregard LA-Vernon LA-Rapides LA-
629 AM CDT Tue Sep 28 2021
...Strong thunderstorms will impact portions of western Rapides,
northern Beauregard, Vernon and northeastern Allen Parishes through
730 AM CDT...
At 628 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Hornbeck to near New Llano to 8 miles
northeast of Elizabeth. Movement was north at 35 mph.
HAZARD...Winds in excess of 40 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
De Ridder, Oakdale, Leesville, Rosepine, Merryville, Boyce, Anacoco,
Elizabeth, Fort Polk, Sugartown, Slagle, Hineston, Lena, Pitkin,
Grant, New Llano, Hornbeck, Hutton, Flatwoods and Otis.
This includes Interstate 49 between mile markers 97 and 109.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with these storms and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.
Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 3150 9269 3147 9271 3145 9268 3140 9269
3140 9261 3078 9260 3075 9361 3083 9355
3088 9357 3093 9353 3100 9358 3103 9351
3109 9356 3111 9354 3124 9356 3128 9353
3128 9344 3136 9339 3135 9295 3151 9273
TIME...MOT...LOC 1128Z 198DEG 29KT 3140 9337 3107 9333 3097 9273
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPH
LandreneauThe Ft Polk radar (KPOE), 50 km away, was scanning. The volume nearest the first event began at 12:35 UTC.
3 flash flood. Local standard time, as filed.
Slow moving heavy thunderstorm produced flooding at Fort Polk and along multiple roads in Vernon Parish. NWS equipment flooded at Fort Polk.
Multiple streets were flooded and impassable in Deridder.
Heavy rain produced street flooding in South Lake Charles.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Louisiana in 2021Every state in 2021This day in weather historyWarnings in Louisiana, September 2021
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: 986609, 986610, 986612.