Although temperatures have been relatively normal for the last few days, the last month has been decidedly colder than normal over the Northwest, as suggested by this map, which shows the deviation from normal for the past 30 days. Much of our region has been 2-4F colder than typical during the past month. Such cold temperatures have brought us a very healthy snowpack.
But the latest model runs are suggesting a much colder period next week, one that would be far colder than we have seen in many years.
Since we are looking forward in time for an extended period, we must think probabilistically and thus I will show you mainly ensemble (many forecast) output.
We can start with European Center ensemble forecasts (51 forecasts) for surface temperatures (max and min) over Seattle. The range of their ensembles are shown by the blue bracket, while the ensemble mean (often very skillful) by the green line. Their single high-resolution run by the black line. 50% of the ensemble members are within the green box.
Note that just after the new year, the high temps drop below freezing and then plateau out around 25-28F. But uncertainty gets large as well.
The US GFS ensemble, shown below, does something similar (Seattle temperature shown, ensemble mean indicated by the black line, high-res member, blue line). Much colder next week, but with substantial uncertainty.
The forecast surface weather maps for next week based on the high-resolution NWS GFS model are chilling, with cold air (blue colors) extending over the whole region.
The latest weather.com forecast (which is generally excellent) is going for cold and sunny early next week as the cold, arctic air spreads south. Is there a chance of snow as the cold air moves in? The answer is yes...but the uncertainties are too large to speculate on that now.
I feel sorry for those Northwesteners who have travelled to warmer climes over the holidays....they are going to suffer terribly next week, while the cold-hardened folks who remained will be more comfortable.
But the latest model runs are suggesting a much colder period next week, one that would be far colder than we have seen in many years.
Since we are looking forward in time for an extended period, we must think probabilistically and thus I will show you mainly ensemble (many forecast) output.
We can start with European Center ensemble forecasts (51 forecasts) for surface temperatures (max and min) over Seattle. The range of their ensembles are shown by the blue bracket, while the ensemble mean (often very skillful) by the green line. Their single high-resolution run by the black line. 50% of the ensemble members are within the green box.
Note that just after the new year, the high temps drop below freezing and then plateau out around 25-28F. But uncertainty gets large as well.
The US GFS ensemble, shown below, does something similar (Seattle temperature shown, ensemble mean indicated by the black line, high-res member, blue line). Much colder next week, but with substantial uncertainty.
The forecast surface weather maps for next week based on the high-resolution NWS GFS model are chilling, with cold air (blue colors) extending over the whole region.
The latest weather.com forecast (which is generally excellent) is going for cold and sunny early next week as the cold, arctic air spreads south. Is there a chance of snow as the cold air moves in? The answer is yes...but the uncertainties are too large to speculate on that now.
I feel sorry for those Northwesteners who have travelled to warmer climes over the holidays....they are going to suffer terribly next week, while the cold-hardened folks who remained will be more comfortable.
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