Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS11 KWNS 210856
SPC MCD 210855
Mesoscale Discussion 0085
NWS Storm Prediction Center Norman OK
0255 AM CST Sat Jan 21 2017
Areas affected...Southeast Louisiana and southern Mississippi
Concerning...Tornado Watch 10...
Valid 210855Z - 211100Z
The severe weather threat for Tornado Watch 10 continues.
SUMMARY...Severe weather including a tornado threat will persist
across southeast Louisiana and southern Mississippi during the
overnight. The greatest threat for tornadoes in the short term is
expected to be from the vicinity of BTR and eastward from Hammond,
LA to Hattiesburg, MS with the increase in supercell development.
DISCUSSION...Recent surface analyses /06-08Z/ indicated a developing
mesolow, now located near BTR, with the strongest pressure falls
from BTR to MCB, while this region and into southwest and
south-central MS also has the coldest cloud tops and greatest
lightning coverage/density. The mesolow is expected to track to the
east-northeast along a northward-developing warm front through
southern MS to central AL (near or just south of a TCL-BHM line) per
trends in mesoanalyses and HRRR forecasts. Forcing for ascent
associated with a progressive and compact shortwave trough moving
into Louisiana at this time will sustain a low-level mass response
across and downstream from WW 10. This response is being observed
per backed southerly low-level winds with an associated increase in
low-level moistening and warm air advection. These factors will
further aid in the development of additional thunderstorms east of
the main BTR-MCB storm complex into southeast MS and southwest AL
through the overnight.
Further strengthening of vertically veering wind profiles and
increasing deep-layer ascent per an apparent coupled jet structure
with the progressive trough suggest supercells should increase in
coverage and intensity across WW 10.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 29449124 30539175 31379168 31879103 32518987 32928915
32928835 31048845 29848835 29078862 28828910 28718955
28858997 28779109 29179122 29449124