- 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.