An area of deepening low pressure is currently migrating northeastwards from the central Atlantic up towards the southeast coast of Iceland. Strong southerly, mild winds will impact the island during Sunday and will also send a front across the British Isles also, erasing a very warm weather here by Monday.

The low deepens towards 970mb off the east coast of Iceland during Monday and with it’s position as well as intensity, strong to gale-force northerlies will develop and this will pull very cold air south over the island from off Greenland.

The below chart shows the low’s position during Monday.

As you can see, the models show a deep, 972mb low right on the east coast of Iceland and with a strong 1026 surface high positioned over northeast Greenland, this will squeeze very cold air much further south than normal for early September. This setup may support hurricane-force winds with well below freezing wind chills. It’s likely to feel more than early winter than early autumn throughout Iceland, especially in the more exposed northern side of the island.

Temperatures by day Monday will widely warm to only 5-8C but with a wind blowing hard out of the north, it’s likely to feel more like freezing or below, even at sea level.

By Tuesday, the winds should ease slightly as the low begins to loose intensity and pushes east away from the island but it will still be very windy with gales likely continuing. Air temperatures may be even colder Tuesday. Note the 850mb temperatures. This suggests air temperature as cold as -10C at 5,000 feet, plenty cold to support snow to low levels, even to sea level and this includes Reykjavik. During Monday, the air gets transported from Greenland south and by Tuesday’s it’s in place with the column cooling as winds blow strong out of the north. Tuesday may support snow to low levels more so than Monday as the  column may take a little time to cool.

The interior of the island which of course is high up may see significant snowfall with daytime highs failing to get above -2 to -4C with wind chills in the dangerously low category of -10C or colder. For low levels and on the coast, cold rain showers are likely to impact Monday but could turn increasingly to snow later Monday, especially after dark when the temperature drops and winds turn colder.