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12/06/2018, 4:51 am EST

U.S. Week 2-4 Outlook: Milder changes.

Highlight: Arctic outbreak risk for late month taken out of the forecast which is adjusted warmer through late December. CIC 4-Week Observation/Forecast Discussion: The week 2-4 forecast is adjusted warmer late month into early January. Stratospheric warming over northwest North America fails to produce the earlier forecast arctic outbreak likely due to the proximity of (warm) north/northeast Pacific Ocean influences. Week 2 Ahead: December 16-22, 2018 (previous forecast below) Comment: An anticipated arctic outbreak from northwest Canada caused by a stratospheric warming event is not indicated and a warmer adjustment in Canada is required. The southern states are adjusted cooler to near normal. The storm track is adjusted much stronger on the West Coast. Week 3 Ahead: December 23-29, 2018 Comment: A zonal (upper) wind profile supports a mild climate while cooler temperatures in the Southwest U.S. is supported by an active southern storm track. Arctic air is not present in the pattern. Week 4 Ahead: Dec. 30, 2018-Jan. 5, 2019 Comment: The strengthening cold in the West-central/Central U.S. is based on expanding snow cover. 4-Week Departure from Normal Regional U.S. HDD Forecast Mid-Atlantic 4-Week Departure from Normal HDD Forecast Vs. Last Year Discussion: The departure from normal weekly HDD forecast is colder than normal for each region indicated and coldest New England and the Southeast U.S. for next week. Steadily, the forecast trends warmer mid-to-late December with warmest anomalies in the West-central Mountain region. Still mild in the Northeast into early January. Note that the mid-December to early January forecast in the Mid-Atlantic is much warmer than last year.