U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus03 kwns 210707 
Storm Prediction Center ac 210706 

Day 3 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0206 am CDT Sat Oct 21 2017 

Valid 231200z - 241200z 

..no severe thunderstorm areas forecast... 

at this time, the risk for severe storms appears negligible across 
the U.S., Monday through Monday night. 

Further amplification of the large-scale pattern across the Pacific 
into western North America appears possible during this period, and 
models continue to suggest that this amplification will begin to 
translate eastward. Downstream of broad, strong ridging centered 
near the Pacific coast, a significant short wave trough is forecast 
to continue digging southeast of the upper Mississippi Valley, 
accompanied by sharpening cyclonic flow from the plains into the 
Appalachians/lower Great Lakes region. When and just how this 
feature consolidates with another perturbation initially near or 
east of the lower Mississippi Valley remain unclear. Rather large 
spread remains evident among the various models and within their 
respective ensemble output concerning this flow evolution and 
associated low-level developments across and east of the Mississippi 

The European model (ecmwf)/ecens remain among the most aggressive indicating 
potential for strong surface cyclogenesis, though mainly Monday 
night across the lower Great Lakes region, when boundary layer 
instability across nearby portions of the upper Ohio Valley and the 
Appalachians remain in doubt. Considerable strengthening of 
lower/mid tropospheric wind fields appears possible in association 
with the southern impulse, across the eastern Gulf states and 
southern into central Appalachians, as early as Monday afternoon. 
However, it appears that widespread cloud cover and rain developing 
ahead of the impulse could contribute to inhibited boundary layer 
destabilization, and minimize convective potential. 

.Kerr.. 10/21/2017