U.S. Severe Weather Forecast (Convective Outlook)

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Storm Prediction Center ac 010541 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1241 am CDT Friday Aug 01 2014 


Valid 011200z - 021200z 


..no severe thunderstorm areas forecast... 


... 
thunderstorms including a marginal severe threat will occur across 
the upper Mississippi Valley and Great Lakes...western South Dakota 
into Nebraska and from Georgia into the Carolinas on Friday. 


... 


The synoptic pattern will undergo little change Friday with large 
upper low centered near the Hudson Bay dominating the eastern half of 
the U.S. And an upstream ridge persisting over the western states. 


At the surface a coastal boundary will move into the Carolinas and southeastern 
Virginia. Farther west a front will continue slowly through southeastern Texas and 
may stall near the Texas coast. A Lee trough will reside across a 
portion of the central and northern High Plains. 


..S Dakota through northern Nebraska... 


Modest /500-1000 j/kg/ MLCAPE is expected east of Lee trough where 
steep middle-level lapse rates will overspread the destabilizing surface 
layer. Storms should develop within zone of deeper mixing along and 
just west of Lee trough and over the Black Hills and spread 
southeastward...possibly aided by a weak middle-level impulse embedded within a 
northwesterly flow regime. Inverted-v boundary layers will support a threat 
of isolated downburst winds. Deep shear of 30-35 knots...steep lapse 
rates and cool middle-level temperatures will also promote a threat for 
isolated large hail. At this time...it does not appear that coverage 
of any severe events will be sufficient to warrant more than 5% 
severe probabilities. 


..upper MS valley through Great Lakes... 


Diabatic warming of the surface layer with dewpoints in the 50s and cool 
temperatures aloft will support moderate /1500-2000 j/kg/ MLCAPE. 
Storms will likely develop within the weakly capped atmosphere 
during the afternoon...aided by weak impulses rotating southeastward around 
upper low circulation. Weak shear will support multicells...but the 
thermodynamic environment appears sufficient for a threat of 
isolated marginally severe hail. 


..GA through the Carolinas... 


A very moist boundary layer with dewpoints in the low 70s will 
accompany the coastal front inland. Widespread clouds and ongoing 
areas of precipitation will limit destabilization and overall severe 
potential with MLCAPE likely remaining at or below 500 j/kg over the 
Carolinas and 500-1000 j/kg over central/southern Georgia. A shortwave trough 
now moving through the lower MS valley will lift northeastward through this 
region...possibly enhancing shear profiles during the day. Ely 
low-level winds veering to southerly and increasing to 30-35 knots at 500 mb 
will support 35-40 knots effective shear. An isolated brief tornado or 
two cannot be ruled out...mainly across NC into southern Virginia where 
stronger low-level veering will exist. Farther south an isolated 
strong wind gust or two will be the main threat over central/southern Georgia. 
Given the expected very marginal thermodynamic environment...threat 
does not appear to warrant more than 5% severe probabilities. 


.Dial/grams.. 08/01/2014 

Mesoscale Discussion


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Storm Prediction Center mesoscale discussion 312218 
nez000-312345- 


Mesoscale discussion 1507 
National Weather Service Storm Prediction Center Norman OK 
0518 PM CDT Thursday Jul 31 2014 


Areas affected...eastern Nebraska 


Concerning...severe potential...watch unlikely 


Valid 312218z - 312345z 


Probability of watch issuance...20 percent 


Summary...a marginal severe threat will likely continue for a few 
more hours this evening across eastern Nebraska. Hail and strong gusty winds 
will be possible. The severe potential should be very isolated and 
ww issuance is not anticipated. 


Discussion...latest surface analysis shows a mesoscale low near Grand 
Island Nebraska with a pocket of low-level moisture over eastern Nebraska where 
surface dewpoints are in the lower to middle 60s f. This is resulting in 
moderate instability with MLCAPE generally in the 1000 to 1500 j/kg 
range. In addition...a subtle shortwave trough is evident on water 
vapor imagery in the middle MO valley. This feature along with the 
instability should sustain ongoing thunderstorm 
development...including marginal supercell structures for a few more 
hours. The WSR-88D vwp shows 0-6 km shear around 30 knots which 
combined with steep low to middle-level lapse rates may be enough for a 
marginal wind and hail threat through mid-evening. 


.Broyles/Mead.. 07/31/2014 


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


Attention...WFO...oax...Gid...lbf... 


Latitude...Lon 42419757 42419814 42069855 41309846 40379778 40179722 
40319665 40959632 41739664 42419757