An Odd Snow Paradox

[Weather-history]

Here is a letter by Richard Dansey of Ludlow, Shropshire written on the 26th October 1898. Unfortunately no specific date is given for this peculiar occurrence.

"One morning in January about 14 years ago we woke up surrounded by a white world with about an inch of snow, but the curious thing was, that the higher you looked up the hills, the less snow there was. At 1200ft high, there was practically no snow and none above this limit; the Clees reaching 1800ft were quite green above about 1000ft. They must have had the storm because the tops of the hills to our west, 1200ft high, had just a trace of snow, while the Clees being to the NE and much higher, the phenomenon was more marked on them. At Church Stretton, 16 miles NNW, the case was similiar -- the valleys were white, while the hills on each side rising to 1500 and 1600ft were bare. At 11am, there was a sharp snowstorm; when it reached the Clees it brought down a thick cloud so I thought they would be white when it lifted; but no, they were green as before. About 4pm, the Clees had another storm of a snowy character -- they were white over in a minute or two and thus the country regained a normal aspect. Up till 4pm, the sight was most peculiar; instead of snow clad hills and green valleys, the case was reversed and there were white valleys and green hills and on every hill there was little snow over 1000ft.

The snow must have been snow on hills, as it could not have formed between the height of the hills and valleys, but somehow the air above 1000ft must have been very much warmer, not only here but over at least half of Shropshire, as shown by the same state of things at Church Stretton. The wind was W to WNW. There was a frost early, as far as I remember, but after 10am. the temperature was slightly above 32F."

[Nick L]

If it was first thing in the morning I would have suggested that the valley floor (and therefore the temperature of the ground) would have been far cooler than the hilltops due to the "frost hollow" effect. But for 4pm this seems a tad unlikely. Perhaps ground temperatures did have something to do with it though preventing it from settling? Very odd nonetheless!

[BornFromTheVoid]

Here's a picture from the end of November last year.

You can see a few inches of snow on the ground. On the mountains to the north, there's no snow for between 100-600m, but plenty of snow above that!

Could it have been cold enough above 600m for snow, too mild between 600 and 100m, and then a small inversion to make it cold enough below 100m?

Edited November 7, 2011 by BornFromTheVoid

[Andy Bown]

I wonder if it was caused by crystallized freezing fog (faux snow) which may not have been on the higher ground.

[Weather-history]

Could it have been cold enough above 600m for snow, too mild between 600 and 100m, and then a small inversion to make it cold enough below 100m?

I don't see how since once snow has melted or partially melted into rain/sleet/wet snow it can not revert back into snow, it could only turn into ice pellets at most.

Edited November 7, 2011 by Mr_Data

[Wynn D Woo]

Could it have been a shallow cloud with persistent snizzle / snow and the higher hills were above this cloud base, certainly a curious situation.

[Aaron]

I've seen numerous pictures of this, in the Lake District, where snow was on the ground near the lakes but between the peaks and the ground, there was no snow.. I can try find the picture I'm thinking of.

Here it is

Edited November 7, 2011 by Aaron

[Nick L]

It probably does have something to do with ground temperatures. Snow was probably falling but unable to settle. That's the only thing I can think of, hopefully someone with more knowledge can answer it!

[Rustynailer]

The ground could have been frozen all over, if it was a shower it will only stick where it actually snows. I have seen Sandown and Shanklin white all over at sea level, yet the hill to their South St Boniface and Ventnor Downs around 700 feet ASL was green because the shower missed there completely.

[weatherobsuk]

I'm thinking of a foehn wind warming up the temperatures higher up the slopes, while the valley floor is sheltered from the directional winds and heating effect.

[recklessabandon]

I've seen numerous pictures of this, in the Lake District, where snow was on the ground near the lakes but between the peaks and the ground, there was no snow.. I can try find the picture I'm thinking of.

Here it is

I think this might all be down to the sun in the case of this picture. This shot shows the south facing slopes of Skiddaw, which a roughly at 30 to 45 degrees, meaning in mid-winter they are pointing directly at the low aspect sun, and thus melting the snow. below this the frost hollows and valley shade maintain the cover, above this, the cold wins out. If you look at the valley to the immediate south west of the summit, it holds snow much further down, and that is a south east facing aspect, thus only getting morning to lunchtime sun, not the more 'radiant' sun from the south and west which is generally more effective and melting.

Also, this effect can also be seen in more extreme ways in the alps, with alternating layers of cold and warm air under benign conditions.

[BornFromTheVoid]

I don't see how since once snow has melted or partially melted into rain/sleet/wet snow it can not revert back into snow, it could only turn into ice pellets at most.

Yeah, that makes sense actually

The reason recklessabandon gave probably fits that situation too.

[johnholmes]

I've seen numerous pictures of this, in the Lake District, where snow was on the ground near the lakes but between the peaks and the ground, there was no snow.. I can try find the picture I'm thinking of.

Here it is

that picture clearly shows where the main freezing level is well up the mountain. Snow had fallen at all levels but only the valley and the ground below the zero isotherm remain snow covered thanks to the sun.

I don't think that follows the initial account given at the start of this thread. Its possible, but I'de need more information than the account gives that it was due to this

intense cold in the valley due to cold pooling with a freezing level part way up the mountain/hill. Dense fog, as some saw last winter, with very low temperatures can give apparent snowfall of a cm and its possible for several cm's over a couple of mornings/days to accumulate?