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The PIT

Question For Johnh

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Another first for me. Now I've seen Snow start to fall due to very heavy rain and evaporative cooling. Today the rain wasn't that heavy yet snow started at 5.4C and with a dew point of 3.3c. Temps started falling very rapidly at this point and half n hour got to the point where I'd expect snow.

I never seen snow start to fall with conditions like that before. So was it because there was a large pool of cold air above ahead of the front. Time about 10.30 onwards.

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Guess Johns missed it but anyone else can answer if they know the answer.

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Guess Johns missed it but anyone else can answer if they know the answer.

not been around much for a couple of days but got your pm a short time ago as I got back home.

In answer it had to be something to do with very cold air quickly arriving above you such that rain with those values soon turned to snow.

Like I said not been around much but the 00z ascents for Watnall and further north might hold the clue. If I subsequently get time I'll have a look at them if I can find them.

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not been around much for a couple of days but got your pm a short time ago as I got back home.

In answer it had to be something to do with very cold air quickly arriving above you such that rain with those values soon turned to snow.

Like I said not been around much but the 00z ascents for Watnall and further north might hold the clue. If I subsequently get time I'll have a look at them if I can find them.

Cheerz John

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I wouldn't think yesterday's change was evaporative cooling, it happened as very cold air flooded down from the north.

Evaporative cooling would be in more borderline snow conditions with light winds.

Snow may be falling at higher levels and with limited warmer air to counteract it, the air over a given area slowly cools as heat is locally removed by the snow melting to rain/sleet as it falls.

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I wouldn't think yesterday's change was evaporative cooling, it happened as very cold air flooded down from the north.

Evaporative cooling would be in more borderline snow conditions with light winds.

Snow may be falling at higher levels and with limited warmer air to counteract it, the air over a given area slowly cools as heat is locally removed by the snow melting to rain/sleet as it falls.

The rain wasn't heavy enough for that. 3.6mm including the snowfall all day so we can rule that out.

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not been around much for a couple of days but got your pm a short time ago as I got back home.

In answer it had to be something to do with very cold air quickly arriving above you such that rain with those values soon turned to snow.

Like I said not been around much but the 00z ascents for Watnall and further north might hold the clue. If I subsequently get time I'll have a look at them if I can find them.

If it's any use John the 1700 ascent for Nottingham.

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Translate please gentlemen.

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Translate please gentlemen.

nothing to explain Pit-my explanation has been given

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nothing to explain Pit-my explanation has been given

I was curious as to why it wasn't what you expected too see.

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