Alert archive / Louisiana / Severe Thunderstorm Warnings in 2020

Severe Thunderstorm Warning 56, NWS New Orleans, LA

April 28, 2020Saint Tammany Parish, Tangipahoa Parish, Washington Parish, Louisiana

NWS New Orleans, LA issued this severe thunderstorm warning at Apr 28, 2020, 5:58 PM CDT for Saint Tammany Parish, Tangipahoa Parish, Washington Parish, Louisiana. It was in force for 47 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Apr 28, 2020, 5:58 PM CDT (22:58 UTC)
Expired: Apr 28, 2020, 6:45 PM CDT
In force: 47 min
Issued by: NWS New Orleans, LA
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

Counties Saint Tammany Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 11.0 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 2051 m above ground
0-6 km bulk shear: 17 kt
0-1 km storm-relative helicity: 47 m²/s²
0-3 km storm-relative helicity: 198 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 severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS New Orleans, LA wrote its last area forecast discussion before this severe thunderstorm warning went out at Apr 28, 4:22 PM CDT, 1 hour 36 minutes earlier.

Area forecast discussion, Apr 28, 4:22 PM CDT, 1 hour 36 minutes before

Area Forecast Discussion
National Weather Service New Orleans LA
422 PM CDT Tue Apr 28 2020

.SYNOPSIS...
Mosaic radar showed convection from southwest Mississippi to
southeast Texas. In addition, IR satellite imagery showed cloud
top cooling over southeast Texas and southwest Louisiana. Latest
surface analysis showed a 1024mb off the Georgia coast and 1004mb
low over west Texas. Southerly flow was present across Texas and
Lower Mississippi Valley. Surface dewpoints were in the 60s and
70s over east Texas, 60s over Louisiana, and 50s over Mississippi.

Upper level analysis showed a short wave from northwest
Mississippi to southeast Texas and clipper system over the
northern and central plains diving southeast. Isotach analysis
showed the northern stream jet of 120 knots from Montana to
northern Colorado on the backside of the clipper.

&&

.DISCUSSION...
HRRR and RAP continue to show convection associated with the
short wave pressing east southeast this afternoon and this
evening. NAM12 and GFS showed lapse rates of 7.0 to 7.5 C/km from
700 to 500mb from southwest Mississippi to southwest Louisiana
this evening. LCH sounding from 12z this morning showed a lapse
rate of 8.6 C/km and surface base cape value 420j/kg. Southerly
winds have modified instability values across east Texas and west
Louisiana. Forecasted surface base cape values increase 600 to 800
j/kg this afternoon but this convection is driven by the short
wave. As the short wave push east, expecting this convection to
push east weakening before midnight.

Wave over northern and central plains will continue to dive
southeast and deepen the main trough over the mid Mississippi
Valley overnight into Wednesday. An associated trough axis and
frontal zone will push into the area early Wednesday. With the
ongoing convection, cautiously looking at this second wave of
convection along the front.

Surface base cape values are expected 300 to 600 j/kg directly
north and east of Lake Pontchartrain but pooling along this
boundary with cape values 1000 to 2000 j/kg west of Lake
Pontchartrain after midnight. Moisture will pool along the
frontal with precipitable water values 1.8 to 1.9 inches. As a
result, will maintain high rain chances with more showers and
scattered embedded storms along the front early Wednesday. A few
strong to severe storms in a squall line are possible with hail
and strong to damaging wind gusts being the main factor but can
not rule out an isolated tornado. Showers and storms will linger
through Wednesday day period as rainfall amounts of 1 to 2 inches
can be expected. Dry conditions are expected through Thursday
through the weekend with warm conditions.

&&

.AVIATION...
Short range models are suggesting convection developing over
southwest Louisiana tracking southeast affecting KBTR, KHUM, KMSY
and KNEW between 23z today and 03z Wednesday. Will use tempo TS to
cover this threat. Cigs will move into the area just before
midnight at OVC030 and fall to OVC010 before daylight while sh/ts
will also be noted as prevailing at NW terminals before daylight
and all remaining terminals after daylight. Some of these TS could
produce strong wind speeds as well.

&&

.MARINE...
Return flow will continue through Wednesday morning ahead of an
approaching cold front. Winds will increase on Wednesday afternoon
and Wednesday night especially behind the front as a moderate
offshore flow once again returns to the coastal waters. Offshore
flow will continue on Thursday and gradually lull by Thursday
night remaining light but shifting around to a southerly direction
over the weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  65  77  55  76 /  70  90   0   0
BTR  65  78  54  76 /  70  90   0   0
ASD  65  79  55  79 /  50  90   0   0
MSY  68  79  61  78 /  50  90   0   0
GPT  68  77  58  76 /  20  90  10   0
PQL  66  80  55  79 /  20  90  20   0

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...None.
GM...None.
&&

In the hours before

Special weather statement, Apr 28, 3:40 PM CDT, 2 hours 18 minutes before

Special Weather Statement
National Weather Service New Orleans LA
340 PM CDT Tue Apr 28 2020

LAZ034>037-046>048-050-MSZ069-282145-
Iberville-Livingston-St. Helena-East Feliciana-Pointe Coupee-West
Baton Rouge-East Baton Rouge-West Feliciana-Amite-
340 PM CDT Tue Apr 28 2020

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT SOUTHEASTERN WEST
FELICIANA...WEST BATON ROUGE...ST. HELENA...SOUTHEASTERN POINTE
COUPEE...NORTHWESTERN LIVINGSTON...EAST FELICIANA...CENTRAL
IBERVILLE...EAST BATON ROUGE PARISHES IN SOUTHEASTERN LOUISIANA AND
AMITE COUNTIES...

At 339 PM CDT, radar indicated strong thunderstorms were located
along a line extending from near Liberty to near Slaughter to near
Ramah. Movement of the line of thunderstorms was southeast at 30 mph.

Wind gusts up to 50 mph are possible with these storms.

Locations impacted include...
Baton Rouge, Zachary, Baker, Denham Springs, Plaquemine, Port Allen,
Jackson, Clinton, Liberty, Greensburg, Oak Hills Place, St. Gabriel,
Walker, Addis, Brusly, Maringouin, Slaughter, Rosedale, Grosse Tete
and Wilson.

Torrential rainfall is also occurring with these storms, and may
cause localized flooding. Do not drive your vehicle through flooded
roadways.

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 3124 9055 3085 9057 3055 9075 3016 9123
      3033 9163 3036 9164 3038 9163 3043 9163
      3081 9121 3100 9108 3100 9106 3102 9106
      3133 9084
TIME...MOT...LOC 2039Z 299DEG 24KT 3124 9082 3078 9115 3038 9159

Local storm report, Apr 28, 4:25 PM CDT, 1 hour 33 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
425 PM CDT TUE APR 28 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0410 PM     TSTM WND DMG     3 W LIBERTY             31.16N 90.85W
04/28/2020                   AMITE              MS   LAW ENFORCEMENT

            MHP BROOKHAVEN REPORTED A TREE WAS BLOWN DOWN AND WAS
            BLOCKING BOTH LANES ON HIGHWAY 24 WEST OF LIBERTY. TIME
            ESTIMATED.

&&

BWAGNER

Local storm report, Apr 28, 4:34 PM CDT, 1 hour 24 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
434 PM CDT TUE APR 28 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0420 PM     TSTM WND DMG     4 N LIBERTY             31.22N 90.80W
04/28/2020                   AMITE              MS   LAW ENFORCEMENT

            TREES REPORTED BLOCKING THE ROADWAY ON HIGHWAY 569 ABOUT
            4 MILES NORTH OF LIBERTY.

&&

BWAGNER

Special weather statement, Apr 28, 4:35 PM CDT, 1 hour 23 minutes before

Special Weather Statement
National Weather Service New Orleans LA
435 PM CDT Tue Apr 28 2020

LAZ036-037-071-282200-
St. Helena-Northern Tangipahoa-East Feliciana-
435 PM CDT Tue Apr 28 2020

...A STRONG THUNDERSTORM WILL AFFECT NORTHERN ST. HELENA...
NORTHEASTERN EAST FELICIANA AND NORTHWESTERN TANGIPAHOA PARISHES...

At 435 PM CDT, a strong thunderstorm was located near Darlington, or
11 miles northwest of Greensburg, moving east at 30 mph.

Winds in excess of 40 mph and pea size hail are possible with this
storm.

Locations impacted include...
Greensburg, Kentwood, Darlington, Easleyville and Tangipahoa.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

LAT...LON 3083 9090 3099 9091 3100 9051 3083 9045
TIME...MOT...LOC 2135Z 262DEG 25KT 3093 9083

Special weather statement, Apr 28, 4:54 PM CDT, 1 hour 4 minutes before

Special Weather Statement
National Weather Service New Orleans LA
454 PM CDT Tue Apr 28 2020

LAZ036-037-048-050-282245-
Livingston-St. Helena-East Feliciana-East Baton Rouge-
454 PM CDT Tue Apr 28 2020

...A STRONG THUNDERSTORM WILL AFFECT ST. HELENA...NORTHWESTERN
LIVINGSTON...SOUTHEASTERN EAST FELICIANA AND NORTHEASTERN EAST BATON
ROUGE PARISHES...

At 454 PM CDT, a strong thunderstorm was located near Pride, or 13
miles north of Denham Springs, moving northeast at 25 mph.

Winds in excess of 40 mph and pea size hail are possible with this
storm.

Locations impacted include...
Greensburg and Montpelier.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

LAT...LON 3049 9093 3071 9095 3096 9058 3066 9058
TIME...MOT...LOC 2154Z 243DEG 23KT 3067 9091

Special weather statement, Apr 28, 5:32 PM CDT, 26 minutes before

Special Weather Statement
National Weather Service New Orleans LA
532 PM CDT Tue Apr 28 2020

LAZ046>050-058-282330-
Iberville-Livingston-Ascension-St. John The Baptist-West Baton
Rouge-East Baton Rouge-
532 PM CDT Tue Apr 28 2020

...A STRONG THUNDERSTORM WILL AFFECT NORTHWESTERN ST. JOHN THE
BAPTIST...ASCENSION...SOUTHEASTERN WEST BATON ROUGE...SOUTHERN
LIVINGSTON...EAST CENTRAL IBERVILLE AND SOUTH CENTRAL EAST BATON
ROUGE PARISHES...

At 532 PM CDT, a strong thunderstorm was located over St. Gabriel, or
8 miles south of Oak Hills Place, moving east at 30 mph.

Winds in excess of 40 mph are possible with this storm.

Locations impacted include...
Gonzales, Oak Hills Place, St. Gabriel, White Castle, Sorrento,
French Settlement, Port Vincent, Springfield, Old Jefferson, Geismar,
Prairieville, Village St. George, Gardere, Carville, Whitehall,
Shenandoah and Killian.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

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.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

LAT...LON 3036 9119 3046 9055 3031 9053 3030 9056
      3026 9059 3022 9057 3020 9060 3017 9058
      3015 9121
TIME...MOT...LOC 2232Z 259DEG 28KT 3025 9109

CAB

The office that day

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

Issued	Product	Office	Counties	Lasted
Apr 28, 2:57 PM CDT	Special Weather Statement	LIX	Pointe Coupee, West Feliciana	63 min
Apr 28, 3:40 PM CDT	Special Weather Statement	LIX	East Baton Rouge, East Feliciana, Iberville, Saint Helena, West Baton Rouge	65 min
Apr 28, 4:35 PM CDT	Special Weather Statement	LIX	Saint Helena	25 min
Apr 28, 4:54 PM CDT	Special Weather Statement	LIX	Saint Helena	51 min
Apr 28, 4:59 PM CDT	Severe Thunderstorm Warning	LIX	Livingston, Saint Helena, Tangipahoa	31 min
Apr 28, 5:04 PM CDT	Tornado Warning	LIX	Livingston, Saint Helena, Tangipahoa	26 min
Apr 28, 5:27 PM CDT	Tornado Warning	LIX	Livingston, Saint Helena, Tangipahoa	33 min
Apr 28, 5:32 PM CDT	Special Weather Statement	LIX	Ascension	58 min
Apr 28, 6:22 PM CDT	Special Marine Warning	LIX		53 min
Apr 28, 6:30 PM CDT	Flash Flood Warning	LIX	Ascension, East Baton Rouge, Iberville, Livingston, West Baton Rouge	3 hr
Apr 28, 3:47 PM CDT	Severe Thunderstorm Warning	LIX	Amite	28 min
Apr 28, 4:10 PM CDT	Severe Thunderstorm Warning	LIX	Amite	50 min
Apr 28, 4:40 PM CDT	Severe Thunderstorm Warning	LIX	Amite, Pike	52 min

Nearby

Severe Thunderstorm Warnings in Louisiana, 2020 Every severe thunderstorm warning in 2020

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.