- Day Three
acus03 kwns 290517
Storm Prediction Center ac 290516
Day 3 convective outlook
National Weather Service Storm Prediction Center Norman OK
1216 am CDT Friday Jul 29 2016
Valid 311200z - 011200z
..there is a marginal risk of severe thunderstorms across the northern plains...
scattered thunderstorms...some severe...are expected to develop
during the late afternoon across the western Dakotas...spreading
into the eastern Dakotas after dark.
Strong middle-level short-wave trough is forecast to eject inland
across British Columbia into sk by the end of the period. Southern influence of this
feature will affect the northern plains late as 500mb speed maximum...near
50kt...translates east along the international border. Associated
surface front will surge across Montana into western ND by late afternoon and
strong boundary-layer heating should remove convective inhibition.
As temperatures warm through the middle 90s scattered thunderstorms should evolve
along the front. This activity will form within a sheared
environment favorable for rotating updrafts and a few supercells
could be noted. Low level jet is forecast to increase across the northern plains
late and this should encourage clustering and perhaps an mesoscale convective system will
evolve after dark within favored warm advection regime.
Poor middle-level lapse rates will affect much of the
country...especially the eastern Continental U.S. Where high precipitable water values will
contribute to scattered convection driven strongly by diurnal influences.
Somewhat stronger middle-level flow will extend across the middle
Atlantic and this may contribute to longer-lived storms. Even
so...forecast instability appears too meager to warrant severe probs
at this time.
Persistent east-southeasterly middle-level flow across southern Arizona would seem to favor
robust convection developing over the high terrain and moving toward
the lower deserts. If day2 convection does not contaminate the air
mass across this region marginal severe threat may be warranted.