Alert archive / Louisiana / Mesoscale Discussions in 2017

Mesoscale Discussion 4

January 2, 201729 parishes in Louisiana; 5 counties in Mississippi; 7 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Jan 2, 2017, 2:06 AM CST for 29 parishes in Louisiana; 5 counties in Mississippi; 7 counties in Texas. It was in force for 114 min.

The area

The outline as issued.

The facts

Issued: Jan 2, 2017, 2:06 AM CST (08:06 UTC)
Expired: Jan 2, 2017, 4:00 AM CST
In force: 114 min
Issued by: the Storm Prediction Center
Chance of a watch: 5%

All 41 counties

Acadia Parish, LA, Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Bienville Parish, LA, Calcasieu Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, De Soto Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Franklin Parish, LA, Grant Parish, LA, Jackson Parish, LA, Jefferson Davis Parish, LA, LaSalle Parish, LA, Natchitoches Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Red River Parish, LA, Sabine Parish, LA, Saint Landry Parish, LA, Tensas Parish, LA, Vernon Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Winn Parish, LA, Adams County, MS, Amite County, MS, Franklin County, MS, Jefferson County, MS, Wilkinson County, MS, Jasper County, TX, Newton County, TX, Orange County, TX, Sabine County, TX, San Augustine County, TX, Shelby County, TX, Tyler County, TX

The radar

The Ft Polk radar (KPOE), 36 km from the middle of the area, began a volume at 08:10 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

Lake Charles Mun, LA (KLCH), launched 00:00Z, 8.1 hours before the alert went out and 132 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: 1365 J/kg
Mixed-layer CIN: -16 J/kg
Mixed-layer LCL: 533 m above ground
0-6 km bulk shear: 46 kt
0-1 km storm-relative helicity: 42 m²/s²
0-3 km storm-relative helicity: 146 m²/s²
Significant tornado parameter: 0.5
Supercell composite: 2.1

Open this sounding in Storm Lab

The text

As transmitted.

041 
ACUS11 KWNS 020806
SWOMCD
SPC MCD 020806 
MSZ000-LAZ000-TXZ000-021000-

Mesoscale Discussion 0004
NWS Storm Prediction Center Norman OK
0206 AM CST Mon Jan 02 2017

Areas affected...Parts of far east TX...LA...and far southwestern MS

Concerning...Severe potential...Watch unlikely 

Valid 020806Z - 021000Z

Probability of Watch Issuance...5 percent

SUMMARY...A marginal threat for a strong winds, hail, and a brief
tornado may exist through the early overnight hours (10Z). This
threat should remain too isolated to warrant watch issuance.

DISCUSSION...Generally elevated convection has developed across
southern and eastern LA along and south of a warm front in response
to strengthening southerly low-level warm air advection. Surface
dewpoints range from 63-69 degrees F across the discussion area,
with even richer low-level moisture just offshore. RAP/HRRR forecast
soundings suggest this convection may remain slightly elevated over
the next several hours given poor low-level rates and surface
temperatures at or near the dewpoint. Regardless, a low-level jet is
forecast to strengthen to around 35-40 kt through 10-12Z, and there
is some low potential for this convection to become surface-based as
it moves northward with the advancing warm front.

In addition, strengthening mid-level winds and ascent with the
approach of a shortwave trough from the west may encourage some
increase in updraft strength with time. Enlarged low-level
hodographs would conditionally support a brief/isolated tornado risk
if a storm could become surface-based, and a strong wind gust or two
may occur. Per latest radar trends, hail approaching severe levels
could also occur with MUCAPE ranging from 500-1500 J/kg and
sufficient effective bulk shear of 35-45 kt. Regardless, the overall
severe threat in the short term (through 10Z) is expected to remain
isolated at best, but this risk should steadily increase through
sunrise and thereafter.

..Gleason/Guyer.. 01/02/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...JAN...LIX...LCH...SHV...

LAT...LON   30079397 30249432 31179444 32029406 32369370 32469291
            32449203 32229141 31739095 31349057 30979064 30529103
            30239197 30019297 30079397

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jan 2, 5:35 AM CST	Mesoscale Discussion	SPC	Acadia, Allen, Beauregard, Bienville, Bossier, Caddo and 18 more	85 min
Jan 2, 6:12 AM CST	Tornado Watch	SPC	Acadia, Allen, Avoyelles, Beauregard, Bienville, Bossier and 27 more	10 hr
Jan 2, 7:48 AM CST	Mesoscale Discussion	SPC	Acadia, Allen, Beauregard, Bienville, Bossier, Caddo and 19 more	57 min
Jan 2, 10:17 AM CST	Mesoscale Discussion	SPC	Ascension, Concordia, East Baton Rouge, East Feliciana, Livingston, Orleans and 10 more	118 min
Jan 2, 11:09 AM CST	Mesoscale Discussion	SPC	Acadia, Allen, Avoyelles, Caldwell, Cameron, Evangeline and 12 more	96 min
Jan 2, 11:22 AM CST	Tornado Watch	SPC	Ascension, Assumption, Catahoula, Concordia, East Baton Rouge, East Feliciana and 21 more	9 hr
Jan 2, 2:03 PM CST	Mesoscale Discussion	SPC	Jefferson, Lafourche, Orleans, Plaquemines, Saint Bernard, Saint Charles and 6 more	117 min
Jan 2, 7:08 AM CST	Mesoscale Discussion	SPC	Clarke, Covington, Jasper, Jefferson Davis, Jones, Kemper and 10 more	97 min
Jan 1, 10:11 PM CST	Mesoscale Discussion	SPC	Archer, Baylor, Bosque, Brown, Callahan, Coleman and 35 more	3 hr
Jan 2, 1:04 AM CST	Mesoscale Discussion	SPC	Anderson, Austin, Bandera, Bastrop, Bell, Bexar and 71 more	86 min
Jan 2, 1:39 AM CST	Severe Thunderstorm Watch	SPC	Anderson, Austin, Bastrop, Bell, Blanco, Bosque and 67 more	59 days
Jan 2, 3:36 AM CST	Mesoscale Discussion	SPC	Anderson, Bastrop, Bell, Blanco, Bosque, Brazos and 44 more	54 min

Nearby

Mesoscale Discussions in Louisiana, 2017 Mesoscale Discussions in Texas, 2017 Mesoscale Discussions in Mississippi, 2017 Every mesoscale discussion 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.