acus03 kwns 220731
Storm Prediction Center ac 220730
Day 3 convective outlook
National Weather Service Storm Prediction Center Norman OK
0230 am CDT Wednesday may 22 2013
Valid 241200z - 251200z
..no severe thunderstorm areas forecast...
some eastward progression of the eastern U.S. Trough is forecast this
period...which will allow the central U.S. Ridge to broaden eastward
somewhat -- though prognosticated to remain fixed over the central U.S.
Through the period. Meanwhile...the western U.S. Trough is expected to
remain in place...though the embedded upper low over the Pacific northwest may
lift slowly northward/northeastward with time.
At the surface...expect the eastern U.S. Cold front to move offshore
early...trailing westward across North Florida...the Gulf Coast...and into Texas
during the afternoon. Meanwhile...a cold front will linger across
the intermountain west...while a Lee trough resides across the
length of the High Plains through the period.
..High Plains from southeastern Montana/southwestern ND southward to eastern nm/far West Texas...
As isolated to scattered convection likely ongoing early in the
period shifts eastward across the plains...a destabilizing but generally
capped boundary layer is expected to exist west of the ongoing
precipitation -- along and ahead of the Lee trough forecast to
reside over the High Plains. Scattered storm redevelopment is
forecast in vicinity of the Lee trough by middle to late afternoon -- as weak
middle-level vorticity maxima translate eastward into the mean ridge
position. With generally modest /aob 30 knots/ middle-level westerlies forecast
atop low-level selys...shear marginally supportive of
organized-rotating updrafts will exist -- particularly where
low-level flow may be locally stronger/more veered. This
combination of ample shear/instability but mean large-scale ridging
suggests that severe threat will remain isolated in general -- and
thus will introduce only a broad 5% threat area over the High Plains
at this time. Pockets of greater threat may be able to be discerned in
later forecasts which could warrant eventual insertion of small
slight risk areas.