Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS03 KWNS 220730
SPC AC 220729
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 AM CDT Wed Mar 22 2017
Valid 241200Z - 251200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN PLAINS...ARKLATEX AND LOWER MISSISSIPPI VALLEY...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN PLAINS...CENTRAL PLAINS...ARKLATEX...OZARKS AND LOWER
TO MID MISSISSIPPI VALLEY...
Wind damage, isolated large hail and a tornado threat is forecast
Friday and Friday night across parts of the southern Plains,
Arklatex and Lower Mississippi Valley.
...Southern Plains/Arklatex/Lower Mississippi Valley...
An upper-level low is forecast to move across the southern Plains on
Friday. At the surface, a low is forecast to move across the Texas
Panhandle into Oklahoma as a dryline advances quickly eastward
across the southern Plains. By midday, surface dewpoints to the east
of the dryline are forecast to be in the lower 60s F in northeast
Texas and in the upper 50s F in east-central Oklahoma. As surface
heating takes place during the day across an uncapped moist sector,
convective initiation appears likely just to the east of the
dryline. This convection should gradually organize into a squall
line being strongly forced by a band of large-scale ascent
associated with the southern Plains upper-level low. The squall line
is forecast to move across much of Arkansas and the western half of
Louisiana during the evening eventually reaching the Mississippi
River late in the period.
Moisture advection will continue on Friday across the southern
Plains and Arklatex as the upper-level system moves from west to
east across the region. This should allow for moderate instability
to develop by late afternoon across parts of eastern Oklahoma and
east Texas. This combined with strong deep-layer shear profiles of
60 to 80 kt should result in a wind-producing MCS as the strong
winds aloft congeal storms into a nearly continuous line. Wind
damage will be possible along the leading edge of this convective
line with the greatest potential in the Arklatex during the evening
as the MCS gains access to higher quality moisture where surface
dewpoints may reach the mid 60s F. In addition, forecast soundings
across the Arklatex Friday evening show low-level shear profiles
sufficient for tornadoes. Supercells that develop in the line or
ahead of the line could be accompanied by a tornado threat. Isolated
large hail may also occur with cells that rotate. An isolated wind
damage and hail threat will be possible in much of the overnight
period as the line of storms approaches the Mississippi River.