March: in like a LION out like a…LION!

March 20, 2013 — Leave a comment

Update Thurs: things changing: snow being brought further south: cold air push back! snow risk for Reigate Sat and Sun! more later, mobile situation, keep watching but wintry weather certainly on the way!

The UK will see some heavy snow over Friday and Saturday as Atlantic fronts bring warmer air spiraling round a LOW pressure to the West bumping into the frigid cold Polar Easterlies blasting from the continent. It looks like the big snow action Friday and Saturday will miss Reigate and stay further north and we will just suffer cold rain, possibly a bit sleety and certainly not pleasant; wind chill temps down to freezing and plenty of rain, up to 10mm!  The North of the country, especially over the Pennines, could see record-breaking March snow.

There is a big North-South divide in air temperature caused by subtle but critical differences in source region: the wind in the North and the South is basically EASTERLY in direction but check the isobars over the country either side of the FRONT on the map showing Saturday’s weather. Over Southern England the isobars can be traced back in a long wide arc over Europe originating somewhere over the Atlantic off Spain and Portugal: much warmer than the source region for the cold Polar easterlies emerging out of the Poles and flowing across a still-cold Russia.  The Atlantic air has 850hPa temps of 0ºC to -5C, whilst the Polar Easterlies drop to -14°C or lower (850hPa is air temps at 1500m, commonly used to measure air mass temperature avoiding surface influences).  So Spring air from the west is trying to make a break through over the country but in a very roundabout way!  Sadly, the Easterlies win next week and flood the entire country with COLD air by Wednesday: expect chilly but dry conditions, frosty nights.

Finally, here’s a special TREAT: take a quick look at the latest GFS forecast which shows a distinct rise in temperatures at the end of next week: a sign of Spring at last? Let’s hope so!

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