SPC Mar 19, 2017 Day 4-8 Severe Weather Outlook

By Newsroom America Feeds at 19 Mar 2017

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0331 AM CDT Sun Mar 19 2017 Valid 221200Z - 271200Z ...DISCUSSION... ...Day 4 and Day 5... The medium-range models begin the day 4 to 8 period with an upper-level ridge in the Great Plains and southwest mid-level flow over much of the western U.S. From Wednesday/Day 4 into Thursday/Day 5, the ECMWF and GFS solutions move an upper-level trough quickly northeastward from the coast of California into the southern and central Rockies. Ahead of the approaching system, a low-level jet is forecast to develop across the southern and central Plains. Isolated thunderstorms will be possible along the western edge of the low-level jet in the southern and central High Plains from late Thursday afternoon into the evening. Uncertainties concerning moisture return are too great to warrant issuing a severe threat area at this time. ...Day 6 to Day 8... The ECMWF and GFS solutions continue to be consistent moving the upper-level trough into the southern and central Plains on Friday/Day 6. It appears that this will happen as a dryline develops in the southern Plains Friday afternoon. Both solutions suggest that convection will develop on the western edge of the moist sector and move eastward across eastern Oklahoma and northeast Texas during the late afternoon. This convection could organize into a line and move across the Arklatex Friday evening especially if the GFS solution is correct which is a bit more aggressive with moisture return. For this reason, will maintain a 15 percent contour in eastern Oklahoma and northeast Texas and expand the area eastward across much of Arkansas and northwest Louisiana. For Saturday/Day 7, the ECMWF and GFS are in agreement concerning the position of the upper-level trough with the system located across the lower Mississippi Valley by Saturday afternoon. However, the GFS solution has varied widely on the position of the trough in the model runs over the last 24 hours. Ahead of the upper-level trough, the models show an unstable airmass in the central Gulf Coast States on Saturday. This setup could result in a severe threat depending upon many factors including the effect of overnight convection and amount of destabilization ahead of the convection. Due to these uncertainties, will not add a 15 percent contour at this time. For Sunday/Day 8, the models continue to move the upper-level trough across the Gulf Coast States and have weak instability across the warm sector. Uncertainty is substantial at this range in the forecast period. Read more



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