U.S. Severe Weather Forecast (Convective Outlook)

Day Three

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Storm Prediction Center ac 081721 

Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1221 PM CDT Thursday Oct 08 2015 

Valid 091200z - 101200z 

..there is a marginal risk of severe thunderstorms across parts of the 
Middle-Atlantic States... 

A few marginally severe thunderstorms with strong wind gusts may 
occur Friday afternoon and early evening in the Middle-Atlantic States. 
Otherwise...isolated to scattered thunderstorms will be possible 
along and ahead of a cold front advancing across the eastern and 
southern u... with storms developing in portions of New Mexico 
and Arizona. 

Models are in general agreement showing a split-flow regime 
developing east of the plains states on Friday. A progressive 
shortwave trough tracking east from the Great Lakes to New England 
and northern Middle-Atlantic States is forecast to phase with a 
stronger/amplifying trough in eastern Canada...while a second trough 
amplifies southeastward through the middle south and Tennessee Valley to the 
central Gulf Coast states and southern Appalachians. At the 
surface...a cold front accompanying the eastern U.S. Troughs will 
advance across the eastern and southern U.S. States. 

..mid-Atlantic states... 
Despite surface temperatures across the warm sector expected to be 
above normal and precipitable water values to around 1.5 inches... 
poor midlevel lapse rates will limit the development of stronger 
destabilization with MLCAPE /per the GFS forecast soundings/ 
expected to range from 500-750 j/kg. Strengthening westerly 
middle-upper level winds across the discussion area through Friday 
afternoon...within the base of the Great Lakes to northeast states 
trough...will contribute to effective bulk shear up to 35-40 knots with 
relatively straight hodographs. Weak 500-mb height falls per 12 
hour and ascent along the cold front suggest the potential for both 
pre-frontal convection/embedded thunderstorms and storm development along 
the cold front. The timing of the cold front may occur across much 
of the marginal severe risk area near or just after peak heating 
when instability should be the strongest. The marginal instability 
and poor midlevel lapse rates will limit updraft strength and 
longevity...though the forecast bulk shear suggests a few storms 
could become organized as multicells or perhaps a supercell. The 
greatest severe threat should be isolated damaging wind gusts. 

.Peters.. 10/08/2015