DISCUSSION: Along most coastlines, the ocean has a very large influence for much of the atmospheric phenomena and temperatures that occur in these locations. With everything else being equal, continental air masses will be more extreme than maritime ones (meaning the land heats up and cools down quicker creating larger temperature departures whereas maritime air masses modify the temperature). We see this come into play across the entire west coast of the U.S., where the coldest air during the winter comes straight from the North American continent as opposed to the milder Pacific Ocean air.
This concept is very much related to portions of western Europe. Typically, a westerly wind advects mild Atlantic air keeping portions of the countries such as Portugal and Spain relatively mild. Over the next week or so, high-pressure systems migrating north and east from the Azores will produce a more north to northeasterly wind over these regions shown above (notice 850mb winds from the north and northeast). This allows for cooler continental air masses to advect chiller temperatures as shown below (2-meter temperature anomaly chart with blues and purples meaning well below average).
While this colder air is in place, these regions, especially in the northern mountains of Spain, have a chance to see snow based on the latest GFS model guidance below (colors and numbers correspond to accumulations in centimeters). The GFS even hints at some light snow making its way all the way down to the northern regions of Portugal. This is uncommon for this region, but not unheard of. In any event, an interesting pattern ahead for southwestern portions of Europe is on the way!
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©2018 Weather Forecaster Joseph DeLizio