Mesoscale Discussion 8

Issued

Jan 2, 2017, 7:48 AM CST (13:48 UTC)

Expired

Jan 2, 2017, 8:45 AM CST

In force

57 min

Issued by

the Storm Prediction Center

The Ft Polk radar (KPOE), 146 km from the middle of the area, began a volume at 13:48 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.

225 
ACUS11 KWNS 021349
SWOMCD
SPC MCD 021348 
LAZ000-ARZ000-TXZ000-021445-

Mesoscale Discussion 0008
NWS Storm Prediction Center Norman OK
0748 AM CST Mon Jan 02 2017

Areas affected...Parts of east TX...western/central LA...and far
southwestern AR

Concerning...Tornado Watch 2...

Valid 021348Z - 021445Z

The severe weather threat for Tornado Watch 2 continues.

SUMMARY...A damaging wind, large hail, and isolated tornado threat
will continue through the morning hours across Tornado Watch 2.

DISCUSSION...A messy convective mode is ongoing across far eastern
portions of Severe Thunderstorm Watch 1 and western parts of Tornado
Watch 2 as of 1345Z. Primary low-level forcing in the form of a cold
front and an attendant MCS will continue to pose mainly a strong to
damaging wind risk as it moves eastward through the morning hours. A
pre-frontal band of broken convection across far east TX into far
western LA continues to exhibit some mid-level rotation within the
strongest cores. Large hail and damaging winds will both be possible
with this pre-frontal activity.

12Z sounding from LCH and reveals a very moist low-level airmass
characterized by surface dewpoints in the low 70s, steep mid-level
lapse rates (8.0 degrees C/km in the 700-500 mb layer), and a
generally veering/strengthening wind profile with height. As diurnal
heating commences over the next several hours, a further increase in
instability is expected, and MLCAPE may become as high as 2000 J/kg
across the pre-frontal warm sector. Some veer-back-veer winds were
noted in the 760-560 mb layer from the LCH sounding, and this casts
some doubt on the strength/longevity of any supercells that may
occur ahead of the cold front. Regardless, there will be a threat
for isolated tornadoes through the morning hours across Tornado
Watch 2, as strong winds in the surface to 850 mb layer (aided by a
low-level jet) encourage effective SRH generally ranging from
200-300 m2/s2 across the warm sector.

..Gleason.. 01/02/2017

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

ATTN...WFO...LCH...SHV...HGX...

LAT...LON   29599423 29769604 30469582 31329528 31639516 32949519
            33609488 33099228 29559201 29599423

Mesoscale Discussions in Texas, 2017Mesoscale Discussions in Louisiana, 2017Mesoscale Discussions in Arkansas, 2017Every mesoscale discussion in 2017

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.