U.S. Severe Weather Forecast (Convective Outlook)

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Day Three

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Storm Prediction Center ac 151629 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1129 am CDT sun Jul 15 2018 


Valid 151630z - 161200z 


..there is a marginal risk of severe thunderstorms across the 
middle-south and Great Basin... 


... 
Isolated strong wind gusts may occur across parts of the mid-south 
and western Great Basin during the afternoon to early evening. 


... 
A weak/remnant mesoscale convective vortex will continue to drift east-southeastward toward 
the lower Ohio River valley today, with related ascent contributing 
to thunderstorm development within a moist and unstable air mass to 
its south. A cluster of semi-organized southeastward-moving storms 
is ongoing late this morning across northern Tennessee, with 
outflows/differential heating likely to focus additional 
thunderstorm development this afternoon mainly across southeast 
Missouri, northeast Arkansas into western portions of Kentucky and 
Tennessee. On the southern fringe of thicker cloud cover to the 
north, daytime heating of a very moist boundary layer consisting of 
middle 70s surface dew points will result in MLCAPE ranging 
2000-3000 j/kg in spite of weak mid-level lapse rates. Isolated 
strong gusts producing localized wind damage will be a possibility 
this afternoon through early evening. 


..southern Oregon and northern portions of California/Nevada... 
A moist air mass exists across the region with the 12z observed 
sounding from Reno, Nevada featuring 0.97 inches of precipitable water, 
which is near the daily Max for observed climatological values. 
Widely scattered thunderstorms are ongoing early today in relation 
to a northeastward-moving shortwave trough, with an additional 
mid-level impulse to approach the region tonight. While wave timing 
appears to be sub-optimal in relation to peak heating, some 
thunderstorm redevelopment should occur this afternoon with aid of 
orographic lift/differential heating. Modest deep-layer shear in 
conjunction with ample heating and a relatively moist air mass could 
support a few locally severe storms with downbursts and small hail. 


..portions of Colorado/Wyoming... 
While a few stronger storms could occur this afternoon, the overall 
organized severe potential is expected to remain limited by 
relatively weak mid-level lapse rates as well as weak wind speeds 
(albeit with some vertical veering) through the low/middle 
troposphere. 


..Minnesota Arrowhead/Lake Superior vicinity... 
Although a strong storm could occur, the potential for severe storms 
across this region should remain marginal or very localized owing to 
lingering cloud cover and modest convergence along the advancing 
front. The overall severe risk currently appears low. 


.Guyer/Gleason.. 07/15/2018 


$$ 

Mesoscale Discussion


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sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 150130 
mnz000-ndz000-150300- 


Mesoscale discussion 1057 
National Weather Service Storm Prediction Center Norman OK 
0830 PM CDT Sat Jul 14 2018 


Areas affected...northeastern North Dakota into far northwestern 
Minnesota 


Concerning...Severe Thunderstorm Watch 277... 


Valid 150130z - 150300z 


The severe weather threat for Severe Thunderstorm Watch 277 
continues. 


Summary...storms, mainly across northeastern North Dakota, may 
continue to pose some severe weather potential into late evening 
before diminishing. An additional weather watch now appears 
unlikely. 


Discussion...forcing for ascent and shear associated with the 
vigorous short wave impulse progressing east of the Canadian 
prairies has provided support for the evolution of a broken squall 
line across southern Manitoba into the vicinity of international 
border area. This includes an evolving cluster of storms straddling 
the eastern North Dakota/Manitoba border, and additional cells as 
far south as areas near/west of Devils Lake. Pre-frontal 
instability, to the east of the axis of stronger daytime heating, 
appears sufficient to maintain this activity eastward across the 
remainder of northeastern North Dakota (mainly northwest through 
north of grand forks) through the 03-5z time frame. This will 
probably be accompanied by at least some risk for strong surface 
gusts before activity diminishes as it begins to ingest drier more 
stable air to the east. 


Farther south, isolated ongoing vigorous thunderstorms to the south 
of Bismarck, seems likely to diminish within the next hour or two, 
in the presence of waning boundary layer instability and weaker 
shear/forcing for ascent. 


.Kerr.. 07/15/2018 


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


Attention...WFO...fgf...bis... 


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