June 27 - Long Range Summary
Canadian air draining into the Eastern half of the country at the start of this week marks onset of noticeably milder conditions ending multiday periods of excessive heat observed during most of June. This does not preclude briefer surges of significant heat as recent model consensus warms the Great Lakes and Northeast back into the 90s at the end of this workweek (Thursday and Friday respectively), before cool air returns next weekend (Jul 2-3). Meanwhile the hottest temperatures of summer underway along the West Coast (including 100s in portions of the Pacific Northwest) will linger into midweek before also subsiding during the latter half of this week. Models are exhibiting much greater divergence than typical across all forecast periods as successive runs struggle with faster low amplitude flow. When averaged over multiday time scales near seasonal temperatures are forecast across the Eastern half of the U.S. most of this week, before sustained above average heat resumes across the South (upper 90s-low 100s) during the 6-10 day period. Cool Canadian air will be slowest to fully depart the Northeast until after the 11-15 day period, but once it does longer range models maintain above average temperatures across the entire Midwest, South, and East in a near sustained manner during the latter half of July at the climatological peak of summer heat.
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