Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0402 AM CST Fri Jan 22 2021 Valid 251200Z - 301200Z ...DISCUSSION... Medium-range models appear to be in reasonably good large-scale agreement through most of the period. Of primary interest from a convective perspective, will be two short-wave troughs expected to move out of the southwestern U.S. and quickly across the south central and then southeastern portions of the country. The first of these features -- initially progged to lie over the Oklahoma vicinity at the start of the Day 4 period (Monday morning) will move quickly east northeastward into/across the lower Missouri/mid Mississippi/Ohio Valleys into Day 5. An accompanying surface low will likewise shift eastward across this same general region, but at this time, it appears that available instability will be quite limited, due to weak lapse rates in the surface to roughly 700mb layer. As such, any potential for severe weather appears low -- below the 15% threshold for areal inclusion. As this system weakens and shifts off the East Coast Day 5 (Tuesday), a second short-wave trough crossing the southwestern U.S. is expected to reach the into the central and southern Plains late Tuesday/early Wednesday (Day 6). The system is then progged to continue eastward to the Tennessee Valley late Day 6/early Day 7, before moving off the Atlantic Coast prior to the start of Day 8. However, a cool/stable boundary layer is forecast to spread southward into the south central and southeastern U.S. in advance of this feature, and thus -- with the primary surface baroclinic zone progged to lie over the northern Gulf of Mexico, only a muted surface response is expected in association with the advance of this system. As such, conditions will likely remain thermodynamically unfavorable for any appreciable severe weather risk through the middle and latter stages of the period.
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