U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 301938 
Storm Prediction Center ac 301937 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0237 PM CDT Tuesday Aug 30 2016 

Valid 302000z - 311200z 

..there is a marginal risk of severe thunderstorms from northestern Montana into northwestern ND... 

an isolated severe storm or two is possible this evening along the 
Montana/North Dakota border vicinity. Other storms are more likely 
later tonight over northwest North Dakota with a threat for mainly 
marginally severe hail. 

..nern Montana through northwestern ND... 

Presence of shortwave ridging and a capping inversion suggest extent 
of surface-based thunderstorm development over the northern High Plains will 
probably remain limited. However...a couple of storms cannot be 
ruled out as the boundary layer continues to warm and mix through a 
deeper layer resulting in weakening convective inhibition. Downburst 
wind and hail will be possible within any afternoon/evening storm 
that develops over northestern Montana. Greater confidence exists that storms 
will develop later tonight within zone of increasing isentropic 
ascent and destabilization on nose of strengthening low level jet from extreme 
northestern Montana into northwestern ND. This activity will be elevated with a risk for 
mainly small to marginally severe hail. 

.Dial.. 08/30/2016 

Previous discussion... /issued 1127 am CDT Tuesday Aug 30 2016/ 

..far eastern Montana/western ND... 
In the wake of very isolated showers/few thunderstorms this 
morning...there is a conditional risk for a high-based supercell or 
two evening /and possibly into the overnight across western ND/ 
should storm development occur near a northwest/southeast-oriented 
quasi-stationary front. The primary uncertainty relates to the 
general lack of large-scale forcing for ascent under the influence 
of the upper-level ridge. Nevertheless...sufficient near-frontal 
heating/confluence near the boundary in conjunction with nocturnally 
strengthening warm-air advection may be sufficient to initiate 
isolated thunderstorms around/after 00z. If storms do 
develop...relatively strong northwesterly winds and 35-40 knots 
effective shear would support a high-based supercell or two capable 
of hail/wind. 

..South Florida/Florida Keys... 
Well to the east of Tropical Depression Nine /reference National 
Hurricane Center for latest details/...there may be some potential 
for low-level southerly winds to increase later today through 
tonight across South Florida/Keys vicinity. This will be in conjunction 
with a very moist air mass with middle 70s f surface dewpoints. Even 
while low-level hodographs could become modestly more 
elongated...mid-tropospheric flow will remain very weak. The overall 
potential for any semi-sustained small supercells is expected to 
remain low. 

..KS to IL/Indiana... 
Semi-focused near outflow and a zone of differential cloud 
cover/heating from Kansas into downstate parts of Illinois/Indiana at 
midday...thunderstorms should diurnally increase this afternoon 
within this corridor. While a few thunderstorms capable of stronger 
wind gusts may occur...the potential for severe-caliber wind gusts 
should remain low overall. 


Mesoscale Discussion

acus11 kwns 292036 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 292035 

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 

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... 


Latitude...Lon 44769953 45569781 46349580 47259375 47249310 46809247 
46199266 45639380 44929560 44289778 44089885 44159937 
44329966 44769953