Happy with this run 

Get the two HP's to link 

 

I would take issue with the use of "only applies" with regards to -6C or -7C and while it does happen  to say "easily" at -3C is pushing it a bit. 

-3C is definitely a better threashold for an ana front (not cold front) in a low wind environment.

Its genuinely rare to get the -6C or -7C T850 when a warm front bumps into cold air anyway, and it isn't necessary in the cold, dry and low wind environment.

This kind of thing (obviously at this range we take nothing literally) would easily produce snowfall for Devon, South Wales and the south west generally outside of Cornwall and the immediate coast.

Arguably if its snow you are looking for these charts are fantastic for rolling the dice for at least one snow event pretty much anywhere. Compare that to a less unsettled northerly or easterly; yes the airmass is colder but outside of Scotland and the coasts you may well end up with nada.

 

-6C seems like a crude average that never actually applies in any normal situation (too high for convective snow, too low for frontal snow).

 

Disagree with that , there will be plenty of times -6c is just right.  Most likely in westerly flows especially in Scotland where the pressure is generally lower and therefore 850hpa layer is lower.

In a westerly with the right combination of pressure and wind speed,  -6c will be right.

In November 2016 we had a covering of snow here from this chart, doesn't look remarkable -4c 850's ,  again low pressure so the 850 layer is lower and gentle westerly winds 

https://www.wetterzentrale.de/maps/archive/2016/cfsr/CFSR_1_2016111818_1.png

The first snow event is this:

I can pretty much guarantee (even at this range) some low lying areas will see wet snow out of this. What I can't guarantee is any particular part of the UK will see snow. But somewhere at sea level will. And a decent wet slushy covering (more than dusting) type amount too probably.

Yes it is Q is correct we have had this discussion before -3 is enough in certain situations especially with any s easterly element (dryer air)

Not to mention also any slack and evaporation elements involved 

 

I would take issue with the use of "only applies" with regards to -6C or -7C and while it does happen  to say "easily" at -3C is pushing it a bit. 

Yes it is Q is correct we have had this discussion before -3 is enough in certain situations especially with any s easterly element (dryer air)

Not to mention also any slack and evaporation elements involved 

 

 

Indeed. This is so underrated.

We are trained to think in terms of beaufort 6-8 winds coming off the North sea or North atlantic and definitely for that you do need T850 to be around -8C because you get little evap cooling and the sea warming the boundary layer.

But get air stangating for any length of time and you can easily be a few more degrees more generous. Add some dry air into the equation from an oncoming warm front and you easily get to -2C or -3C. Add snow cover and weeks of low level cold and you get to about 0C.

I'm not suprised the models are showing quite a bit of snow.

The upper level temps are easily low enough for snow provided its caused by ana fronts in a stagnant environment.

The -6C or -7C benchmark that people use for 850hpas only applies if the wind is strong and the precipitation is convective. Snow can easily fall with uppers around -3C given the right sort of conditions.

The wind speed is just as important as temperature when it comes to forecasting snow. The lower, the better. High wind speeds require colder temperatures.

 

I don't know the figures but the Midlands snow storm in December 1990 produced a lot of snow which was on very wet ground (rain to snow event) from uppers that were not that low. 

 

 

I don't know the figures but the Midlands snow storm in December 1990 produced a lot of snow which was on very wet ground (rain to snow event) from uppers that were not that low. 

To be honest pretty much any frontal snow event (not cold front) will have high uppers. I'd wager most snow we see in any given year (outside of Scotland and the coasts) falls in conditions where T850 is warmer than -6C. 

These charts are fantastic for early December in rolling the dice for the entire UK. They are less good if you want consistent cold or snow that sticks around for any length of time. But we can't seriously complain about that in the first week of December!

 

 

I don't know the figures but the Midlands snow storm in December 1990 produced a lot of snow which was on very wet ground (rain to snow event) from uppers that were not that low. 

This one:

https://www.theweatheroutlook.com/twodata/reanalysis.aspx?year=1990&month=Dec&dom=09&var=tmp&region=Eur&level=850&hour=00

 

 

Right over Shropshire.

Nah, he has a unique micro climate where mild westerlies prevail.

This is a very significant snow event.

Won't happen like this ofc. But the fact that these sorts of charts are showing up this early is fantastic!

https://meteologix.com/uk/model-charts/euro/united-kingdom/snow-depth/20201205-0900z.html

Have a look at the ECM snow depth charts.

Usual caveats apply.

Point is you don't get these sorts of charts with no interest!

In many ways for model watchers this event is amazing because it keeps us on our toes. Its not like 2010 where snow was guaranteed. Alot of marginal snow events keeps the anticpation going! Plus it isn't late February where this sort of stuff would just be annoying.

https://meteologix.com/uk/model-charts/euro/united-kingdom/snow-depth/20201205-0900z.html

Have a look at the ECM snow depth charts.

Usual caveats apply.

Point is you don't get these sorts of charts with no interest!

 

 

In many ways for model watchers this event is amazing  because it keeps us on our toes. Its not like 2010 where snow was guaranteed. Alot of marginal snow events keeps the anticpation going! Plus it isn't late February where this sort of stuff would just be annoying.

 

This is a very significant snow event.

Won't happen like this ofc. But the fact that these sorts of charts are showing up this early is fantastic!

No it's not, you are misreading the charts. That would be snow for a time in Scotland and rain elsewhere, then soon rain for all.

 

Nah, he has a unique micro climate where mild westerlies prevail.

 

 

No it's not, you are misreading the charts. That would be snow for a time in Scotland and rain elsewhere, then soon rain for all.

No that is a highly coherant warm front coming into established cold air.

That's a 5-10cm scenario in mainland western Britain away from the coasts. Potentially even more than that. You'd even get snow in NI temporarily.

As a result, the likelihood of above-average temperatures only moderately exceeds that of below-average temperatures. Nevertheless, the chances of cold spells are higher for this season than has typically been the case in recent years.#

This is worth remembering from the contingency planners NOV-JAN 2021

 

 

No it's not, you are misreading the charts. That would be snow for a time in Scotland and rain elsewhere, then soon rain for all.

I'd disagree , I think ...THINK , you'd probably get snow for a time as the front comes into cold air before turning back to rain for most but not the hillier regions