U.S. Severe Weather Forecast (Convective Outlook)

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Storm Prediction Center ac 300534 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1234 am CDT Tuesday Aug 30 2016 


Valid 301200z - 311200z 


..no severe thunderstorm areas forecast... 


... 
while thunderstorms with potential for a few locally strong wind 
gusts will occur from a portion of the Mississippi Valley and upper 
Great Lakes region...overall severe threat is expected to remain 
limited this period. 


... 
With the exception of some moderately strong flow within the base of 
a shortwave trough moving through northern California and into the northern 
rockies...the strongest flow aloft will primarily exist north of the 
international border throughout the period. A shortwave trough will 
move within the moderate westerly flow aloft across northern Quebec while 
shortwave ridging builds in its wake ahead of the northern California/northern rockies 
shortwave. Expansive sub-tropical ridge extending from the Central 
Plains through the southeast will remain largely in place. 


At the surface...a cold front is initially expected to extend from 
central Upper Michigan southwestward into far northwest Iowa and then nwwd back across southern South Dakota. 
Eastern portions of this front will gradually continue southeastward while western 
portions remain largely stationary across the Central Plains. 


..upper Great Lakes...Upper/mid MS valley... 
weak to moderate middle-level lapse rates -- I.E. Less than 7 degree c per 
km -- are anticipated within the airmass ahead of the cold front. 
Although the degree of instability will be tempered by these weak 
lapse rates and preceding showers and/or cloud cover...ample 
low-level moisture /dewpoints in the upper 60s/ will likely result 
in quick airmass destabilization once daytime heating begins. 
Convergence along and ahead of cold front should result in widely 
scattered to scattered thunderstorm coverage. Storm intensity will be 
limited by the generally low instability and modest middle-level flow. 
A few stronger storms may be possible in areas where more diurnal 
heating is realized and/or storm mergers occur but severe coverage is 
currently expected to remain low enough to preclude any severe 
probabilities. 


..cntrl/southern Florida... 
Widespread showers and thunderstorms are expected across central/southern Florida 
throughout the period as the tropical system currently moving slowly 
nwwd towards the central Gulf of Mexico continues to advect deep 
tropical moisture into the region /00z mfl sounding sampled precipitable water of 
2.40 inches/. NAM guidance forecasts an increase in low-level winds 
along East Coast of Florida. However...given the anticipated westward motion of 
the system and only modest strengthening...the areal expansion of 
the stronger low-level wind forecast by the NAM appears much too 
broad. Other guidance also agrees with the scenario of a more 
confined wind field. As such...tornado probabilities are expected to 
remain below 2-percent. 


.Mosier/Hart.. 08/30/2016 


$$ 

Mesoscale Discussion


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acus11 kwns 292036 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 292035 
mnz000-sdz000-ndz000-292230- 


Mesoscale discussion 1608 
National Weather Service Storm Prediction Center Norman OK 
0335 PM CDT Monday Aug 29 2016 


Areas affected...northestern South Dakota across western/central Minnesota 


Concerning...severe potential...watch unlikely 


Valid 292035z - 292230z 


Probability of watch issuance...20 percent 


Summary...scattered storms are likely to form from eastern South Dakota into central 
Minnesota later this afternoon with only a marginal severe wind and hail 
threat. 


Discussion...surface map shows a trough from northwestern Minnesota into eastern South Dakota and 
southwestward into western Nebraska but convergence is weak. However...85-90 f 
temperatures now exist across much of central South Dakota with middle 80s across 
central Minnesota where strong heating persists. While upper support is 
currently lacking...very subtle height falls will occur later today 
in association with a low-amplitude shortwave trough to the north. In 
addition...the existence of cool midlevel temperatures and heating 
in the low-levels will maximize lapse rates and 
instability...allowing for at least temporarily strong updrafts as 
shear will not favor organization. Models are consistent in showing 
storms forming within the surface trough by 22z from northestern South Dakota into 
Minnesota...and then dying by early evening. Hail may occur briefly with 
the stronger cores initially...then a threat of severe wind gusts 
before activity creates outflow and stabilizes the area. 


.Jewell/guyer.. 08/29/2016 


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


Attention...WFO...dlh...mpx...fgf...fsd...abr... 


Latitude...Lon 44769953 45569781 46349580 47259375 47249310 46809247 
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