Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0212 AM CDT Sat Sep 25 2021 Valid 281200Z - 031200Z ...DISCUSSION... Medium-range forecast guidance is in relatively good agreement through Day 5/Wed. The upper trough over the Pacific Northwest early Day 4/Tue will broaden/expand eastward across much of the West through Wednesday. Meanwhile, an amplified upper ridge over the Plains will shift eastward toward the MS Valley. Southerly low-level flow will allow for a narrow corridor of Gulf moisture spreading into the southern Plains and mid-MO Valley. This could support some localized potential for strong storms Days 4-5/Wed-Thu. However, large-scale forcing will remain weak with any severe potential dependent on smaller-scale processes not well resolved at longer timescales. Beyond Day 5/Wed, forecast guidance continues to trend toward the development of a cut-off upper low over the eastern U.S. Should this occur, severe potential likely would become small as surface high pressure and associated continental trajectories would cut off Gulf moisture across much of the central/eastern states. Furthermore, guidance also continues to show a weaker/lower-amplitude western trough/cut-off low developing later in the period, with any stronger shortwave impulses passing north of the international border. Read more LIVE: spc.noaa.gov
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