Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0350 AM CDT Wed Jul 14 2021 Valid 171200Z - 221200Z ...DISCUSSION... Medium-range guidance continues to indicate further amplification of the large-scale flow across the eastern Pacific into western North America this coming weekend. This appears likely to include considerable further expansion of a prominent mid-level high shifting north of the Four Corners, with ridging likely to encompass much of the Intermountain West, Rockies and northwestern Great Plains by early next week. This regime could still be accompanied by the periodic evolution of organizing thunderstorm clusters across parts of the Southwest. There may also be at least some potential for strong to severe storm development across the Columbia Plateau into parts of the northern Rockies, in association with short waves emerging from offshore larger-scale troughing. However, much will probably depend on smaller-scale features characterized by low predictability at this extended range, and it is not yet obvious that this will be accompanied by much more than relatively isolated and/or marginal severe weather potential. Gradually, it appears that short wave perturbations progressing around the amplified mid-level ridge will contribute to amplifying mid-level troughing digging southeast of Hudson Bay during the early to middle portion of next week. At this point it seems possible that thunderstorm activity could become fairly widespread along and ahead of an associated cold front advancing across New England and the lower Great Lakes into upper Ohio Valley vicinity, as well as within pre-frontal surface troughing east of the Blue Ridge into southern New England, next Wednesday. It is not yet clear that deep-layer mean wind fields and shear will be more than weak to modest, but a seasonably moist boundary-layer may contribute to sufficient instability to support organizing lines and clusters with the potential to producing damaging wind gusts. Read more LIVE: spc.noaa.gov
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