Following record heat to the Central Plains on Monday, the heat will continue this week as a zonal flow dominates the pattern.
Denver-DIA hit 81° today which is 34° above the normal high of 47°. This difference between the actual high & the normal high was the second largest ever recorded for Denver. The only larger difference occurred on Dec 5, 1939 when Denver was 35° above normal. #cowx
— NWS Boulder (@NWSBoulder) November 27, 2017
I don’t think the heat will be as intense for the remainder of this week, but the large majority of the nation will still experience temperatures up to 20 degrees above average. The only exception will be portions of the West Coast, where cooler air coming off the Pacific ocean will keep temperatures at bay.
The European ensemble mean forecast temperatures for this week shows the above normal temperatures dominating the Lower 48’s weather:
The reason for this warmth is a zonal flow, which I briefly mentioned earlier in this article. With a zonal flow, the jet stream is flat, with upper-level winds moving from the west to east. This helps brings in warmer air from the mid-latitudes, opposed to the cold air locked up in Canada. A zonal flow helps keep the weather relatively quiet. There aren’t any significant storms that are forecast to impact the US this week because the atmosphere isn’t favorable for it. The graphic below shows the forecast geopotential height anomaly for this week. This illustrates that temperatures will be above average for the U.S..