Alert archive / Louisiana / Flash Flood Watches in 2017

Flash Flood Watch 7, NWS Shreveport, LA

August 27, 20177 counties in Texas; 17 parishes in Louisiana

NWS Shreveport, LA issued this flash flood watch at Aug 27, 2017, 4:00 AM CDT for 7 counties in Texas; 17 parishes in Louisiana. It took effect at Aug 27, 2017, 4:06 AM CDT. It was in force for 4 days.

The area

The counties it named.

The facts

Issued
Aug 27, 2017, 4:00 AM CDT (09:00 UTC)
In effect from
Aug 27, 2017, 4:06 AM CDT
Expired
Aug 31, 2017, 8:11 AM CDT
In force
4 days
Issued by
NWS Shreveport, LA
Flood severity
None
All 24 counties

Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Caldwell Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Red River Parish, LA, Sabine Parish, LA, Union Parish, LA, Webster Parish, LA, Winn Parish, LA, Angelina County, TX, Cherokee County, TX, Nacogdoches County, TX, Panola County, TX, Sabine County, TX, San Augustine County, TX, Shelby County, TX

The radar

The Shreveport radar (KSHV), 62 km from the middle of the area, began a volume at 09:02 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Shreveport, LA (KBAD), launched 00:00Z, 9.0 hours before the alert went out and 59 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Shreveport, LA at 00:00Z on 2017-08-27Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 509 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Shreveport, LA at 00:00Z on 2017-08-27The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 82 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
509 J/kg
Mixed-layer CIN
-54 J/kg
Mixed-layer LCL
953 m above ground
0-6 km bulk shear
18 kt
0-1 km storm-relative helicity
82 m²/s²
0-3 km storm-relative helicity
103 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this flash flood watch went out, 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 this flash flood watch went out at Aug 26, 11:32 PM CDT, 4 hours 28 minutes earlier.

Area forecast discussion, Aug 26, 11:32 PM CDT, 4 hours 28 minutes before
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Hazardous weather outlook, Aug 26, 4:16 PM CDT, 11 hours 44 minutes before
Hazardous Weather Outlook
National Weather Service Shreveport LA
416 PM CDT Sat Aug 26 2017

ARZ050-051-059>061-070>073-LAZ001>006-010>014-018>022-OKZ077-
TXZ096-097-108>112-124>126-136>138-150-151-272130-
Sevier-Howard-Little River-Hempstead-Nevada-Miller-Lafayette-
Columbia-Union-Caddo-Bossier-Webster-Claiborne-Lincoln-De Soto-
Red River-Bienville-Jackson-Ouachita-Natchitoches-Winn-Grant-
Caldwell-La Salle-McCurtain-Bowie-Franklin-Titus-Camp-Morris-Cass-
Wood-Upshur-Marion-Smith-Gregg-Harrison-Rusk-Panola-
416 PM CDT Sat Aug 26 2017

This Hazardous Weather Outlook is for portions of south central
Arkansas, southwest Arkansas, north central Louisiana, northwest
Louisiana, southeast Oklahoma and northeast Texas.

.DAY ONE...Tonight...

Scattered showers and thunderstorms will be possible today across
the four region area due to the effects of Tropical Storm Harvey
still located well to our south. Daytime heating will be limited
due to extensive cloud cover, but a few stronger bands of heavy
rainfall could materialize during the afternoon. Otherwise, no
hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Sunday through Friday...

The track of Harvey is still somewhat uncertain through next week,
but rainfall amounts are expected to increase across our region by
the middle and latter part of the week as Harvey finally begins to
shift farther north and east. Additional rainfall totals next week
of three to six inches with isolated higher amounts close to eight
inches are possible across much of east Texas and north Louisiana
with enhanced sea breeze bands through mid to late week. This may
pose a flash flooding potential, but the uncertainty with Harvey's
eventual track makes this threat still somewhat unclear at this
time.

.SPOTTER INFORMATION STATEMENT...

Activation of emergency management personnel...amateur radio
operators and storm spotters will not be needed through tonight.

LAZ017-TXZ149-152-153-165>167-272130-
Sabine-Cherokee-Nacogdoches-Shelby-Angelina-San Augustine-
416 PM CDT Sat Aug 26 2017

This Hazardous Weather Outlook is for portions of northwest
Louisiana, east Texas and northeast Texas.

.DAY ONE...Tonight...

Scattered showers and thunderstorms will be possible today across
the four region area due to the effects of Tropical Storm Harvey
still located well to our south. Daytime heating will be limited
due to extensive cloud cover, but a few stronger bands of heavy
rainfall could materialize during the afternoon. The outermost
bands could also present a weak tornadic potential through the
evening hours. Otherwise, no hazardous weather is expected at
this time.

.DAYS TWO THROUGH SEVEN...Sunday through Friday...

The track of Harvey is still somewhat uncertain through next week,
but rainfall amounts are expected to increase across our region by
the middle and latter part of the week as Harvey finally begins to
shift farther north and east. Additional rainfall totals next week
of three to six inches with isolated higher amounts close to eight
inches are possible across much of east Texas and north Louisiana
with enhanced sea breeze bands through mid to late week. This may
pose a flash flooding potential, but the uncertainty with Harvey's
eventual track makes this threat still somewhat unclear at this
time.

.SPOTTER INFORMATION STATEMENT...

Activation of emergency management personnel...amateur radio
operators and storm spotters should not be needed through
tonight.

19

The office that day

Everything else NWS Shreveport, LA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 27, 3:42 AM CDTRiver Flood WarningSHVAngelina, Houston, Polk, Trinity, Tyler8 days

Nearby

Flash Flood Watches in Louisiana, 2017Flash Flood Watches in Texas, 2017Every flash flood watch in 2017

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.