U.S. Severe Weather Forecast (Coup d'œil sur la convection)

Day Three

acus01 kwns 270450 
Storm Prediction Center ac 270449 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1149 PM CDT Friday Aug 26 2016 

Valid 271200z - 281200z 

..there is a marginal risk of severe thunderstorms across the Midwest... 

..There is a marginal risk of severe thunderstorms from the eastern Dakotas into western 

A few strong to severe thunderstorms with hail and gusty winds will 
be possible across parts of the Midwest into western Minnesota and 
the eastern Dakotas. 


High precipitable water plume currently extends around the western periphery of upper 
anticyclone from the Southern Plains...arcing across the middle MS valley. 
Within this plume...several embedded disturbances are noted...often 
associated with and enhanced by convection. Latest NAM guidance 
suggests a weak surface low will develop in association with one of 
these features over southeastern Iowa...tracking into WI by 18z. This 
evolution should allow synoptic front to advance northward extending from 
the surface low...east-southeastward across Lake Superior into Northern Ohio by early 
afternoon. Seasonally strong southwesterly middle-level flow on the order of 
35kt should extend across Illinois into WI in association with this 
feature...enhancing the shear for potential organized updrafts. 
Even so...considerable amount of convection may be ongoing at the 
beginning of the period as broad warm advection zone shifts northeastward in 
response to veered low level jet. This should impede or delay surface heating 
such that daytime instability should be retarded with weak lapse 
rates expected. If sufficient buoyancy can develop near the warm 
front there may be a localized threat for a few 
supercells...otherwise gusty winds are the primary threat with 
organized multi-cell clusters. 

..ern Dakotas/western Minnesota... 

Pronounced middle-level short-wave trough will progress across the 
Dakotas to near the Minnesota border by 28/00z with 500mb temperatures 
expected to cool to near -16c north of 50kt speed maximum. Despite the 
notable short wave...surface convergence is expected to remain weak in 
response to this feature but strong boundary-layer heating should 
contribute to a narrow corridor of instability beneath steepening 
lapse rates. Robust updrafts should develop just ahead of this 
feature during the afternoon as temperatures warm into the upper 70s 
to near 80f. Isolated strong winds or hail may accompany this 

.Darrow/leitman.. 08/27/2016 


Mesoscale Discussion

acus11 kwns 270235 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 270235 

Mesoscale discussion 1598 
National Weather Service Storm Prediction Center Norman OK 
0935 PM CDT Friday Aug 26 2016 

Areas affected...parts of northwest into north central MO 

Concerning...Tornado Watch 458... 

Valid 270235z - 270330z 

The severe weather threat for Tornado Watch 458 continues. 

Summary...an additional severe weather watch is not anticipated. 

Discussion...the forward propagating portion of the ongoing 
convective cluster...now advancing across/northeast of 
Chillicothe...appears to be in the process of weakening. As 
boundary layer instability continues to wane...there appears little 
support for substantive further re-intensification. Vigorous 
thunderstorms do persist in a narrow band near and to the cool side 
of the trailing outflow boundary...southwestward into the Kansas 
City area. While it may not be out of the question that this 
activity could generate some strong surface gusts before diminishing 
during the next couple of hours...the severe weather potential...in 
general...seems low enough to allow the Tornado Watch to expire as 
scheduled at 03z. 

.Kerr.. 08/27/2016 

..please see www.Spc.NOAA.Gov for graphic product... 


Latitude...Lon 39279485 39989406 40189313 39589235 38599426 38769508