U.S. Severe Weather Forecast (Convective Outlook)

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Day Three

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Storm Prediction Center ac 180440 


Day 3 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1140 PM CDT Tue Oct 17 2017 


Valid 201200z - 211200z 


..no severe thunderstorm areas forecast... 


... 
thunderstorm potential will increase across the south-central US and 
over the upper Mississippi Valley. 


... 


Strong short-wave trough will spread across the northern 
intermountain region Friday into the northern High Plains by 21/12z. 
Height falls ahead of this feature should encourage short-wave 
trough over the Southern Plains to eject into the arklatex region. 
Thunder probabilities will increase ahead of these features from the 
lower Sabine River into the upper MS valley. 


1) south-central US - southern-stream short-wave trough will eject 
across nm into the Texas South Plains early in the period. This feature 
is expected to aid northward transport of low-level moisture and a 
notable increase in precipitable water from the Upper Texas coast into central OK where 
values should be on the order of 1.5". Forecast lapse rates are not 
particularly steep ahead of this feature but buoyancy should be more 
than adequate for convection in advance of the trough. Some 
consideration has been given to introduce 5% severe probs due to the 
marked increase in moisture as deep-layer shear will increase ahead 
of the trough such that convection could become sustained in nature. 
If later guidance is more aggressive with buoyancy then severe probs 
may be warranted. 


2) upper MS valley - low-level warm advection will increase across 
the upper MS valley during the day3 period as low level jet strengthens from 
Kansas into The Arrowhead of Minnesota. Air mass is initially quite dry across 
this region but sustained moistening should lead to adequate 
instability for weak elevated convection after dark well ahead of a 
sharp cold front that will surge into this region by the end of the 
period. 


.Darrow.. 10/18/2017 


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