J2Ski Snow Report - March 30th 2017

Brucie wrote:why does it almost always indicate a heavy fall of snow?

It doesn't.

Check the first few locations on our "snowiest locations" list at https://www.j2ski.com/snow_forecast/. Not much snow in the forecast for much of the US at the moment is there?

As for Europe, next week is looking full of precipitation and quite possibly cold for April too.

Watch the GFS visualization on Ventusky; lots for The Alps and around the 18th a potential fizzer rolling a bunch into the Pyrenees...
https://www.ventusky.com/

...and that storm's a nice example; if subsequent model runs (or the eventual reality) push it slightly North then the snow now forecast for Andorra will end up being rain in Bordeaux.

Ventusky is nothing to do with us; but we think it's a very cool and easy way to get the big picture of the forecast model outputs.

I shall consult my spies in resort and let you know if the metre and a half materialises in Soldeu next weekend.

Brucie wrote:I shall consult my spies in resort and let you know if the metre and a half materialises in Soldeu next weekend.

Well, keep checking Ventusky in the meantime; that storm's a really nice illustration - if you see J2Ski's forecast swing the snow back out again, it'll be because GFS has decided the storm's going somewhere else (or fading completely).

It's tough being a weather forecaster. As they say in athletics: 'you're only as good as your last race'. Guess that might apply to financial market callers and weather callers as well.
I have noticed over the past decade that weather forecasts are mostly on the money so not sure why snow forecasts are mostly wrong.
I do hold serious doubts about the real estate industry (letting agents) subsidising websites and getting calls which are fanciful at best. Money speaks many languages and I am yet to be convinced that writing snow forecasts is not one of them.
Sorry to have a tin hat but just calling it like I see it.

Admin wrote:Our forecasts are driven, as we've discussed before, by GFS and the way to view them is as the "latest best guess".

Trouble is the GFS is pretty poor at guessing the weather in the mountains. The GFS is a hydrostatic model, hydrostatic models use pressure as vertical coordinates in the forecast (e.g. make forecasts at specific isobars) and essentially make general approximations about topography. The main reason that J2ski and other similar websites use the GFS is because the data are free. This guide explains how it works and what the limitations are http://www.soaringmeteo.ch/modelEN.pdf

The ECMWF (European Centre for Medium-Range Weather Forecasts) model uses altitude and more accurately accounts for topographic effects on weather systems and is therefore generally more accurate, unfortunately the data are not free.

J2ski also seems to have problems with the post processing of the raw data. In today's forecast for Zermatt J2ski is forecasting thundersnow on Saturday, https://en.wikipedia.org/wiki/Thundersnow this is an extremely rare weather phenomenon that I have never ever seen during the 27 years that I have lived in the region. It is also forecasting 2 cm of snow at village level even though the temperature is forecast to be 8⁰C! Local forecast for night time temperature is 3⁰C.

I think that's a reasonably fair summary of GFS vs ECM Mr Beep, although in our case we do in fact pay a 3rd party post-processor who apply their own topographical modelling to the GFS data. Snow-Forecast - I believe - apply their own topo processing to GFS although theirs, IMHO, appears to amplify some of the long-range swings.

We watch the large-scale output of both (and several other) major models on a regular basis and there's really not much to choose between them nowadays; sometimes ECM will pick up a pattern change while GFS is still swinging around wildly, and other times GFS will go first. GFS 7-day improved noticeably when they increased their resolution a few years ago.

We've also seen several falls this season that ECM hasn't picked up on - I'm pretty sure that the "mini retour d'Est" that briefly hosed Valfrejus and Bardoneccia in early December was one of those (I remember that because I didn't believe the forecast at the time and dismissed it as a glitch until I was sent a picture of a buried chairlift...).

SwingBeep wrote:J2ski is forecasting thundersnow on Saturday,

Fair point on the thunder; we've noticed that a few times too and have fed back to our suppliers.

SwingBeep wrote:It is also forecasting 2 cm of snow at village level even though the temperature is forecast to be 8⁰C! Local forecast for night time temperature is 3⁰C.

The 8C is the daytime max, although there does seem to be a data error there as the snow line is shown only coming down to 1970m (i.e. above the town).

Edited to add :- there is another update being processed now.

Good to see some discussion on this one. Providing a ballpark forecast is pretty important and I fail to understand that there is not a model which is much much better than what is clearly a failed model. The science is so good everywhere else compared to 20 years ago that one might expect that past data in the mountains would be able to be matched with real time data to make a better call. Forecasting 20 cm snow when it is 8C is just plain nuts and it needs to stop. People who blow a stack of money coming skiing in a heatwave should be better served.
Whether or not the letting agents have a finger in the pie is unknown but I sort of have a suspicious bone and have seen this going on for decades. Hence the assertion. Interesting how this plays out though.

Soldeu 24/4 - 27/4

226cm snow forecast.

This modelling model really needs addressed! Any 'post processor' with an ounce of common sense can see that this is fanciful at best!