On Feb 13, 4:28*pm, wrote:
I have been struck over the last few days by the huge difference between snow cover at the top of Hampstead Heath (380 feet ASL) and nearby but slightly lower locations such as Swiss Cottage. Although the top of the Heath is generally a little snowier than nearby lower spots, for the recent snow event the difference has been remarkable. At the top of the Heath near the car park behind Jack Straw's Castle, the snow depth has been a consistent 5-8cm since Monday morning (11th) with trees and shrubs plastered in snow even until this morning. It is a true winter scene. Only a few hundreds yard away where we live at a height of about 250 feet, the snow has been 2-3 cm in depth with the trees losing their cover from Tuesday. Down in Swiss Cottage, no more than 1.5 miles from the top of the heath at a height of about 180 feet, there is now scarcely any snow to be seen. Other parts of London are now similarly snowless. I presume the difference is attributable to a combination of the lapse rate, orographic uplift and fewer buildings. Still, it is rather remarkable given the relatively small altitude differences involved.

The urban heat island effect has also been stark this week. Where I
live in Aldersbrook, just south of Wanstead, has retained the snow far
better than the immediate surrounding areas, even though it is only
18m asl. Though it is only 7 miles from the City it is surrounded by
very open green space - almost making it semi-rural, with Wanstead
Flats to the south, the City of London cemetary to the east, and
Wanstead Park to the north, and Bushwood to the west, the estate is a
bit of an island in green. The easterly feed has also helped - with no
obvious warming from central London. Still quite a few patches left.