U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus03 kwns 010717 
Storm Prediction Center ac 010716 

Day 3 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0216 am CDT Monday Sep 01 2014 

Valid 031200z - 041200z 

..no severe thunderstorm areas forecast... 

isolated severe thunderstorms are possible across the upper 
Mississippi Valley and northern plains. 

..upper MS valley/northern plains... 

Weak middle-level height rises are expected across the upper MS valley 
Wednesday...well ahead of short-wave trough that should progress 
into eastern Montana by the end of the period. Beneath weak short-wave 
ridging...boundary layer moisture is expected to advance northward across 
the MO valley into eastern South Dakota/southern Minnesota where lower 70s surface dew points 
should be in place by late afternoon. In the absence of significant 
large scale forcing...diabatic heating and weak low level warm 
advection will prove instrumental in convection that evolves across 
this region. Latest NAM/GFS develop scattered precipitation within the 
warm advection zone across the upper MS valley. It/S not clear 
where this activity will be rooted and updrafts could be elevated 
rather than ingesting higher quality boundary layer parcels. Even 
so...there is some concern robust updrafts will evolve as forecast 
soundings exhibit veering wind profiles with height and sufficient 
bulk shear for supercells. Have introduced 5 percent severe probs 
to account for this uncertainty. If it becomes more clear warm 
advection convection will root into high moisture airmass then 
severe probs will be raised accordingly. 

Farther west...difluent high-level flow will spread across the northern 
High Plains of Montana into the western Dakotas by 04/00z. Upward vertical velocity should 
increase across this region after dark and the Prospect for scattered 
convection should increase along cold front during the latter half 
of the period. One negative for organized severe across this region 
is the limited low-level moisture. Despite the Ely boundary layer 
flow it appears moisture/instability sufficient for strong updrafts 
may struggle to advect into ND prior to frontal passage. 

.Darrow.. 09/01/2014