Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0357 AM CST Sat Dec 26 2020 Valid 291200Z - 031200Z ...DISCUSSION... ...Tuesday/Day 4 and Wednesday/Day 5... The medium-range models move an upper-level trough across the Four Corners region on Tuesday as a low-level jet strengthens in the Great Plains. A cold front is forecast to move southeastward into the central Plains as a surface low moves northeastward into the mid Missouri Valley. Thunderstorm development will be possible along and ahead of the front from Kansas southward into Oklahoma and Texas during the late afternoon and evening. Weak moisture return should minimize the severe potential in most areas. The greatest severe threat may be confined to north-central Texas where surface dewpoints could reach the mid to upper 50s F. The upper-level trough is forecast to move eastward across the High Plains on Wednesday as the cold front advances quickly southeastward into the Arklatex and mid Mississippi Valley. Model forecasts suggest a line of thunderstorms will be likely ahead of the front during the afternoon. As this line interacts with a moist airmass over the lower Mississippi Valley during the afternoon, a severe threat could develop. Although instability is forecast to remain weak, strong large-scale ascent and abundant deep-layer shear may be sufficient for a wind damage threat. At this time, the greatest potential would be in east Texas eastward across southern Louisiana during the late afternoon. Uncertainty is significant and if instability remains very weak ahead of the line, then the severe threat could be minimal. ...Thursday/Day 6 to Saturday/Day 8... Model forecasts move the upper-level trough into the lower Mississippi Valley on Thursday as the moist sector shifts eastward across the eastern Gulf Coast states. Thunderstorms will be possible Thursday ahead a cold front from Mississippi eastward to Georgia. Storm development could also occur in parts of the Carolinas. The greatest potential for a severe threat would be in Georgia where surface dewpoints are forecast to reach the 60s F. If instability remains very weak across the moist sector, any severe threat could be minimal. On Friday and Saturday, a progressive upper-level trough is forecast to move from the southern Rockies eastward to the lower Mississippi Valley. Model forecasts suggest that moisture return ahead of the system will be minimal, which could limit any severe potential ahead of the trough.
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