Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0335 AM CDT Thu Jul 15 2021 Valid 181200Z - 231200Z ...DISCUSSION... Medium-range models indicate that upper flow could amplify further across the eastern Pacific into western North America through the early portion of next week. Thereafter, the offshore mid-level low may be forced inland across the British Columbia coast. It remains unclear the extent to which this may contribute to suppression of the downstream ridging across the Canadian Prairies. However, it still appears that a vigorous short wave trough to the northeast of the ridge will dig southeast of Hudson Bay and contribute to mid-level trough amplification across the Northeast by the middle of next week. There appears at least some signal in latest output, that an influx of monsoonal moisture into the northern intermountain region may accompany a perturbation migrating around the northwestern periphery of the mid-level ridge by next Monday. This is when associated forcing for ascent and destabilization may become most conducive to the evolution of a cluster of thunderstorms, posing at least some risk for severe weather, across parts of eastern Oregon and the Columbia Plateau into parts of the northern Rockies. It now appears that a cold front associated with the amplifying mid-level trough in the East may advance southeast of the St. Lawrence Valley and lower Great Lakes region as early as late Tuesday, before continuing into and across the middle and northern Atlantic Seaboard by Wednesday night. While wind fields and shear may remain modest to weak, and initially higher moisture content may be swept southward by a preceding impulse, a plume of steeper lower/mid-level lapse rates may advect in from the west-northwest and contribute to increasing convective instability supportive of at least some organized severe weather potential. Read more LIVE: spc.noaa.gov
http://dlvr.it/S3mxWz
