ost prominent in today’s medium-range forecast are the reversal in the North Atlantic oscillation/Pacific North America pattern(s) beginning later this week and indicating warmth in the West fades while emerging across the eastern half of the nation. The -PNA pattern should also lead to an increase in rain and snow in California in the extended-range.

The Canadian Operational model identifies a swath of heavy rain in the 5-day forecast extending from north of Hawaii into the Canadian West Coast and Washington. The 5-day forecast indicates over 10 in. of rain in this zone with high spots approaching 20 in. Widespread flooding complicated by high wind strikes Washington (and northward)!

Heading Into meteorological winter where is the early season cold air mass source region? Typically, early winter brings gathering arctic air masses in Siberia but not this year. The frigid and snowy early winter regime is locked-in over Alaska. Pieces of this air mass have ejected into the East U.S. in the current pattern although that risk is likely eliminated once we're into December.

The negative North Atlantic oscillation (-NAO) is impressive…surging toward -3.00 later this month. Implied is storminess and following cold into the East. The 12Z GFS has less of a storm for next week in the Northeast. The Scandinavia Index drops to -4.00 to -6.00 which indicates an unusually cold trough for Northwest Eurasia which will include cold temperatures and snow for that region.