U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus02 kwns 221729 
Storm Prediction Center ac 221728 

Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1228 PM CDT Thu Mar 22 2018 

Valid 231200z - 241200z 

..there is a marginal risk of severe thunderstorms Friday evening 
across parts of the north Central Plains into middle/lower Missouri 

Strong thunderstorms may impact portions of the north Central Plains 
into lower Missouri Valley late Friday afternoon into Friday night. 
Some of these could be accompanied by a risk for severe hail. 

Models indicate that the remnants of an elongated, deep mid/upper 
low will begin to gradually shift inland of the Pacific coast during 
this period. It appears that one emerging significant impulse will 
pivot across the Pacific northwest through Alberta/Saskatchewan by 
late Friday night, while another continues to dig off the Pacific 
northwest coast. These developments are expected to contribute to 
the evolution of positively tilted large-scale troughing across much 
of much of the west, where split belts of mid-latitude westerlies 
emerging from the Pacific may become more in phase. 

Downstream, large-scale upper ridging is forecast to continue 
developing east of the U.S. Rockies and Canadian prairies through 
the upper Great Lakes region, the Mississippi Valley and parts of 
the southeast, while troughing lingers across eastern Canada and 
much of the northeast. It still appears that a significant impulse 
within the southern branch of the mid-latitude westerlies, initially 
in the vicinity of The Four Corners region at 12z Friday, will 
progress through the broader scale anticyclonic flow across the 
Colorado rockies into the middle/lower Missouri Valley region by 12z 

In association with this latter short wave, models indicate that 
modest surface cyclogenesis is possible across parts of eastern 
Colorado into Kansas during the day Friday. This will probably be 
accompanied by strengthening southerly low-level flow across the 
southern and Central Plains into the mid/lower Missouri Valley. 
Beneath a belt of strengthening mid-level flow on the southern 
periphery of the impulse, a destabilizing environment within the 
warm sector of the low, and along a developing warm frontal zone, 
may become supportive of at least some risk for strong/severe storm 
development late Friday afternoon into Friday night. 

..Central Plains into mid/lower Missouri Valley... 
A southerly return flow is already underway from portions of the 
western Gulf of Mexico through the southern and Central Plains. By 
late Friday afternoon, it appears that moisture characterized by 
precipitable water in excess of 1 inch and surface dew points in the 
lower 60s may reach the vicinity of the deepening surface low. 
Models indicate that this will contribute to at least weak cape on 
the order of 500-1000 j/kg. 

It does appear that inhibition associated with warm elevated mixed 
layer air may suppress thunderstorm development to the south of the 
surface frontal zone. However, strong boundary layer 
heating/mixing, coupled with forcing associated with the upper 
impulse, may support the initiation of storms across the High Plains 
of southeast Wyoming/northeast Colorado and western Nebraska late 
Friday afternoon. Severe weather potential across this area remains 
unclear, but at least a risk for small hail and locally strong gusts 
appears to exist in stronger storms through early evening. 

Somewhat better potential for vigorous thunderstorm development may 
evolve Friday evening into Friday night farther to the east, across 
parts of southern Nebraska into the Missouri Valley, as stronger 
mid-level height falls shift eastward and a strengthening (50+ kt at 
850 mb) low-level jet enhances/focuses lift associated with 
lower/mid tropospheric warm advection. Activity should be rooted 
above a pronounced near surface stable layer, but the environment 
may become conducive to the risk for at least marginally severe 

.Kerr.. 03/22/2018