U.S. Severe Weather Forecast (Convective Outlook)

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 
northern rockies... 

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. 

..northern rockies... 
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 

.Guyer.. 08/19/2018