- Day Three
acus02 kwns 190556
Storm Prediction Center ac 190556
Day 2 convective outlook
National Weather Service Storm Prediction Center Norman OK
1256 am CDT sun Aug 19 2018
Valid 201200z - 211200z
..there is a marginal risk of severe thunderstorms across the
Lower/Middle Mississippi River valley to Tennessee Valley and the
Isolated severe thunderstorms will be possible on Monday across the
Lower/Middle Mississippi River valley to Tennessee Valley as well as
the northern rockies.
..Lower/Middle Mississippi Valley to Tennessee/Ohio valleys...
On Monday, a shortwave trough will continue to spread
east-northeastward over the middle Mississippi River valley and
Midwest. Even as this system begins to lose amplitude, a belt of
seasonally strong low/mid tropospheric winds will overspread parts
of the mid-south, Tennessee Valley into the lower Ohio Valley. The
potential for relatively widespread cloud cover and precipitation
still casts uncertainty regarding the overall magnitude/extent of
monday's severe risk. This uncertainty precludes a categorical
slight risk, although one could ultimately be warranted somewhere
across the mid-south and middle Mississippi Valley vicinity,
possibly as far north as portions of Illinois.
Regardless, potentially influenced by differential heating and
outflows, storms should diurnally redevelop and intensify across the
mid-south region along, or more so, ahead of a cold front amidst
moist/confluent low-level flow during the afternoon. The exact
degree of destabilization is especially more uncertain with
northward extent into the Midwest/Ohio Valley, but bands of storms
could develop near the front/surface low during the afternoon
pending sufficient destabilization in the wake of early-day
convection. Overall, flow fields generally characterized by 30-35 kt
effective shear magnitudes would support sustained multicells and a
few supercells capable of primarily wind damage Monday afternoon and
evening, although some hail and tornado risk may exist as well.
Forcing for ascent and moderately strong winds aloft will accompany
a deamplifying shortwave trough over the region. Coincident with
ample vertical shear (40+ kt effective), it appears that sufficient
moisture and buoyancy will exist over the region for the possibility
of some stronger storms capable of hail and/or downbursts Monday
afternoon and early evening.
..maximum risk by hazard...
Tornado: 2% - marginal
wind: 5% - marginal
hail: 5% - marginal