U.S. Severe Weather Forecast (Convective Outlook)

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Day Three

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Storm Prediction Center ac 110825 


Day 3 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0225 am CST Tue Dec 11 2018 


Valid 131200z - 141200z 


..there is a marginal risk of severe thunderstorms Thursday into 
Thursday night across the Sabine and lower Mississippi valleys...and 
north central Gulf Coast vicinity... 


... 
Strong thunderstorms may impact parts of eastern Texas into the 
lower Mississippi Valley and north central Gulf Coast vicinity 
Thursday into Thursday night, accompanied by at least some risk for 
severe weather. 


... 
Models suggest that mid/upper flow could amplify further through 
this period, with troughing and ridging within split belts of 
westerlies emanating from the mid-latitude Pacific largely in phase 
across the eastern Pacific into western North America. Downstream 
of the ridging, models indicate that a vigorous short wave trough 
within the southern stream will dig southeast of the southern 
rockies, before turning eastward across the Southern Plains, where a 
significant embedded lower/mid-tropospheric cyclone may evolve and 
deepen while progressing toward the lower Mississippi Valley. 


While the ensemble mean output of the various models are fairly 
similar with the depiction of the evolving pattern, spread among the 
ensemble members and among the deterministic output of the various 
models has been, and remains, rather large. This not only includes 
the evolution of the mid-latitude perturbation, but also its 
interaction with a belt of westerlies emanating from the subtropical 
eastern Pacific. 


Further complicating matters concerning the assessment of any 
associated severe weather potential, the boundary layer over the 
Gulf of Mexico will only be in the process of beginning to modify in 
the wake of antecedent cooling and drying. And substantive warm 
sector low-level moistening inland of coastal areas remains in 
doubt. 


..East Texas/lower Mississippi Valley/Gulf Coast... 
Models suggest that an influx of upper 50s to lower 60s f surface 
dew points across southeast Texas into Louisiana is possible during 
the day Thursday. It appears that this probably will occur in the 
wake of an early period band of convection that will progress across 
and east of the lower Mississippi Valley. However, an evolving dry 
slot may allow for sufficient insolation to contribute to weak to 
modest boundary layer destabilization, beneath fairly cold mid-level 
temperatures across parts of eastern Texas into Louisiana. If this 
occurs, deep layer shear probably will be sufficient to support a 
risk of severe storms, possibly including a couple of supercells. 


Otherwise, somewhat better boundary layer moisture return appears 
possible ahead of an evolving secondary surface low near coastal 
areas, from southeast Louisiana into the western Florida Panhandle 
Thursday night. This may also contribute to an environment 
conducive for supercells, including the risk for a tornado or two. 


.Kerr.. 12/11/2018 


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