U.S. Severe Weather Forecast (Convective Outlook)

Day Three

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Storm Prediction Center ac 290445 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1145 PM CDT Friday Aug 28 2015 

Valid 291200z - 301200z 

..no severe thunderstorm areas forecast... 

scattered thunderstorms will be possible on Saturday from the 
southern Great Lakes southward to the Gulf Coast. Additional 
thunderstorms will also be possible from the Desert Southwest 
northward into the central and northern rockies. 

A relatively vigorous upper trough will continue eastward across the northwestern 
U.S. With low surface pressure from British Columbia southward into the Pacific northwest. 
Strengthening wind fields and lift will result in bands of showers 
and perhaps a few thunderstorms mainly west of the Cascades. Locally 
strong/gusty winds with low-topped convection will be possible from 
late afternoon through evening across coastal Washington and Oregon...but 
likely non-severe. 

Elsewhere...widespread thunderstorms will occur during the day 
across Florida into southern Georgia and Alabama as Ely flow maintains moisture off the 
Atlantic. Daytime heating as well as the presence of a weak upper 
low/trough with attendant cool temperatures aloft will aid in 
diurnal destabilization supporting daytime storms. 

.Jewell.. 08/29/2015 

Mesoscale Discussion

acus11 kwns 282301 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 282301 

Mesoscale discussion 1754 
National Weather Service Storm Prediction Center Norman OK 
0601 PM CDT Friday Aug 28 2015 

Areas affected...boundary waters of northestern Minnesota 

Concerning...severe potential...watch unlikely 

Valid 282301z - 290100z 

Probability of watch issuance...20 percent 

Summary...isolated severe hail and damaging wind may accompany 
scattered storms developing southeast from Ontario through about 03z. 
Relatively limited spatiotemporal extent and overall amplitude of 
the threat should preclude a Severe Thunderstorm Watch issuance. 

Discussion...a right-moving supercell just north of Rainy Lake appears 
likely to have a severe hail core per recent mrms mesh data within 
increasing thunderstorm development across northwestern Ontario. This activity 
appears to be tied to a weak shortwave impulse evident in water 
vapor imagery crossing the border region that should also be 
supporting an increase in low-level warm air advection per afternoon model forecasts. 
The majority of cams appear a bit overeager with convective 
development thus far. But on the fringe of moderate middle-level wnwlys 
and probable steep middle-level lapse rates...it appears plausible that 
a couple transient supercells and/or a multicell cluster develops 
east-southeast across the boundary waters area through at least sunset. 
Weakening shear with southern extent and increasing mlcin will likely 
result in diminishing intensity towards late evening. 

.Grams/Darrow.. 08/28/2015 

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


Latitude...Lon 48759278 48249080 47769091 47419144 47349209 47469282 
47769346 48059380 48619361 48759278