Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0354 AM CDT Tue Oct 20 2020 Valid 231200Z - 281200Z ...DISCUSSION... ...Friday/Day 4 to Monday/Day 5... On Friday, the medium-range models are in reasonable agreement, moving an upper-level trough across the Intermountain West. At the surface, a cold front is forecast to move southeastward into the Ohio and mid Mississippi Valleys. Although instability is forecast to be weak ahead of the front, a marginal severe threat can not be ruled out Friday afternoon in pockets that destabilize the most. On Saturday, the models continue in reasonable agreement with an upper-level trough in the western U.S. and west-southwest mid-level flow from the Great Plains to the Great Lakes. At the surface, a cold front is forecast to be located from the lower Mississippi Valley into the southern Appalachians. Instability along the front is forecast to be very weak, suggesting that the severe threat could be limited Saturday afternoon. ...Sunday/Day 6 to Tuesday/Day 8... Model solutions diverge in the latter half of the Day 4 to 8 period. Some solutions develop an upper-level trough across the southern High Plains by Monday with other solutions keeping the trough further west in Desert Southwest. The faster solutions suggest that a large area of precipitation will develop from parts of the southern Plains northeastward to the Ohio Valley from late Sunday night into Monday. If this scenario pans out, then thunderstorms would be possible along the northern edge of the moist sector on Monday from parts of Texas east-northeastward to the Tennessee Valley. The faster solutions suggest the thunderstorm potential would continue into Tuesday as a cold front moves across the southern Appalachians and Southeast. Under this scenario, instability would be relatively weak along and ahead of the front keeping any severe threat marginal. Predictability remains low late in the Day 4 to 8 period.
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