U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus02 kwns 261728 
Storm Prediction Center ac 261727 

Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1227 PM CDT Thu Apr 26 2018 

Valid 271200z - 281200z 

..there is a marginal risk of severe thunderstorms across the 
eastern Oregon/western Idaho vicinity... 

Isolated strong thunderstorms capable of downburst winds may occur 
from parts of eastern Oregon into southwestern Idaho later Friday 
afternoon and evening. 

A large upper trough -- comprised of numerous smaller-scale features 
-- is forecast to affect the eastern half of the U.S. Day 2, while 
ridging prevails across a large portion of the intermountain west 
and into western portions of the Great Plains. Still farther west, 
an upper low moving east across the eastern Pacific is progged to 
move onshore over the northern California/Oregon vicinity. 

At the surface, a cold front is forecast to shift eastward across 
the West Coast states into the Great Basin with time, ahead of the 
advancing upper low. Meanwhile in the east, a cold front is 
expected to shift southward across the Great Lakes and plains 
states, and into the Midwest/Ohio Valley areas through the end of 
the period. 

..eastern Oregon/western Idaho vicinity... 
Modest, high-based instability is forecast to develop through the 
afternoon in conjunction with daytime heating, supportive of 
isolated thunderstorm development over the region. Though degree of 
cape will remain limited, and thus storms largely weak/disorganized, 
a deep, dry sub-cloud layer (inverted v-type boundary layer 
thermodynamic profile) expected across the area may support 
evaporatively aided downdrafts -- possibly reaching severe levels 
locally. Greatest risk will be in the late afternoon time frame, 
with convection diminishing after sunset. 

..maximum risk by hazard... 
Tornado: <2% - none 
wind: 5% - marginal 
hail: 5% - marginal 

.Goss.. 04/26/2018