Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0335 AM CDT Mon Oct 05 2020 Valid 081200Z - 131200Z ...DISCUSSION... Medium-range models continue to indicate that an initially strong, zonal mid/upper jet, emerging from the northern mid-latitude Pacific, will undergo considerable amplification late this week through next weekend. It appears that this will include the evolution of significant large-scale troughing migrating inland of the Pacific coast, across the Great Basin, Rockies and Great Plains by early next week. By next Sunday, deepening surface troughing and embedded cyclogenesis to the lee of the Rockies may contribute to potential for the development of a substantive southerly return flow off the Gulf of Mexico, which could continue into Monday. This could contribute to sufficient destabilization to support the evolution of organized severe storms across parts of the Great Plains into Mississippi Valley, in the presence of strong vertical shear. However, considerable spread exists within and among the various models concerning the synoptic and sub-synoptic developments, at this extended range. And latest model output suggests that deep-layered low-level moisture return may be complicated by the preceding inland migration of a tropical cyclone late this week into early next weekend. This cyclone (currently Tropical Depression Twenty-Six) is forecast to intensify to hurricane strength across the Gulf of Mexico within the next few days, then migrate inland across the north central Gulf coast by Friday night before weakening. It too could be accompanied by a risk for severe weather, in the form of tornadoes. However, reinforcement of potentially cool air across much of the Gulf States, in the days prior to landfall, contributes to uncertainty concerning the extent of this potential inland of immediate coastal areas.
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