U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus02 kwns 191721 
Storm Prediction Center ac 191720 

Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1220 PM CDT Tue Jun 19 2018 

Valid 201200z - 211200z 

..there is a marginal risk of severe thunderstorms across parts of 
the southern and Central Plains...lower Missouri 
Valley...mid-Atlantic and Pacific northwest... 

A few severe thunderstorms are possible on Wednesday across parts of 
the central and Southern Plains, lower Missouri Valley, mid-Atlantic 
and Pacific northwest. 

..southern and Central Plains/lower Missouri Valley... 
An upper-level low will move southeastward into the northern part of 
the Central Plains on Wednesday as an associated shortwave trough, 
extending southward from the low, moves eastward across the southern 
and Central Plains. At the surface, a cold front is forecast to be 
located from northern Oklahoma extending northeastward into eastern 
Kansas and northwest Missouri by afternoon. Ahead of the front, 
surface dewpoints in the upper 60s to near 70 f should contribute to 
the development of moderate instability with thunderstorm 
development taking place along the front during the mid to late 
afternoon. Several clusters of storms are expected to develop from 
Oklahoma northeastward into northwest Missouri and move eastward 
across the region during the late afternoon and early evening. 
Although deep-layer shear is forecast to generally weak ahead of the 
front, steep low-level lapse rates could be enough for a marginal 
wind damage threat especially in areas that destabilize the most. 
Hail could also occur with the stronger updrafts. 

A shortwave trough will move eastward across the central 
Appalachians on Wednesday. At the surface, a cold front should be 
located across southern Pennsylvania with a low developing across 
far northern Virginia during the afternoon. Surface dewpoints near 
70 f from near the front and southward will aid destabilization with 
the development of a pocket of moderate instability possible by 
early afternoon. As low-level convergence increases, thunderstorm 
development will likely take place in the vicinity of the front 
during the afternoon. Forecast soundings in eastern Virginia 
Wednesday afternoon show 0-6 km shear in the 30 to 40 kt range. This 
combined with steep low-level lapse rates may be enough for 
marginally severe multicells around peak heating. Strong wind gusts 
would be the primary threat. 

..Pacific northwest... 
An upper-level ridge will be in place across the western U.S. On 
Wednesday as a shortwave trough moves northeastward to near the West 
Coast by afternoon. At the surface, a cold front will advance 
eastward into the Pacific northwest. Ahead of the front, surface 
dewpoints mostly in the 50s f should result in an axis of 
instability ahead of the front in western Oregon. Thunderstorms that 
develop along the front during the afternoon may have a potential 
for marginally severe wind gusts and hail due to the instability, 
steep lapse rates and moderate deep-layer shear. 

..maximum risk by hazard... 
Tornado: 2% - marginal 
wind: 5% - marginal 
hail: 5% - marginal 

.Broyles.. 06/19/2018