• The Chatel Snow Report

14/12/2018: Today's Update... 6.30pm...


6.30pm:

The brighter weather never really arrived today and if anything, the afternoon trended cloudier, which was a bit of a surprise. Hopefully, the cloud will clear for tomorrow mornings opening...


The models so far this evening are following the trend of this morning (though the ECMWF is not yet out) and there will be further comment on the outlook for next week on tomorrow morning's forecast page.


The latest GFS run has upped the precipitation amounts again for Sunday / Monday in comparison to its 6z output and interestingly, the really hi-res AROME model is suggesting a slightly lower snow/rain limit than the GFS for the early hours of Sunday - which could make things interesting. Again, further comment on this tomorrow morning, when much more of the Sunday/Monday rain and snow event will be in range of the Arome model.


So, tomorrow is the start of several months of lift operations and skiiing and snowboarding in the wonderful Chatel ski area. There should be at least a couple of updates from the mountain during the day, if the technology allows...



12.45pm:

It is brighter, but still rather cloudy here, with some hazy sunshine poking through at times.

The 6z model runs this morning continue the confused picture regarding the weekend snowfall. GFS 6z has trimmed its precipitation by up to about 20mm of rain equivalent precipitation and it does suggest that most of the precipitation will fall between 1am and 10am on Sunday, when the 0c isotherm will be at its highest (1800m to 2250m to 1950m) - suggesting much of the snow will be in the upper half of the ski area. This may or may not be correct and the snow/rain limits remain rather uncertain. These revised figures should filter through onto the popular snow forecast app in a couple of hours.


The Arpege model is sticking to its theme of predicting underwhelming amounts of precipitation. The graphic below from Meteociel.fr shows its prediction up to 7am Monday (note: there may be some snowfall after this on Monday morning).

The numbers on the graphic are precipitation totals in rain amounts - so you need to convert by a ratio of very approximately 1:10 to get snowfall estimates for the higher ground in cm.


One point of interest from this graphic is to note the different totals forecast for the Chamonix valley - which in this precipitation event is showing double the amount to that of Chatel! Often, this area sees more precipitation than the Chamonix valley, however, this again underlines the fact why precipitation forecasts issued for that valley are often not representative or appropriate for this area, despite being only a relatively short distance apart.


Further changes to this precipitation event are still to be expected and it will be interesting to see what the estimates from the highest res models are when the event comes into their ranges tomorrow.


Next update expected to be this eve... on the eve of a new season...




10.25am:

The weather is yet to brighten up here in Chatel with some cloud still hanging around, though it is thinning at times, so hopefully the sunshine will return before too long.


This morning's forecast mentioned some noticeable model differences related to amounts of rain and snow this weekend and also for the further outlook. For the first issue, it is best to wait until the models have updated again during the day before having another look, so there should be a post regarding that issue during the afternoon.


For the model differences for next week, below are a selection of operational charts from the Meteociel.fr website. The first 6 charts follow the progress of the big 3 models out to the 144hr timeframe, with the last 3 charts showing the GFS, the new GFS "Parallel" and the ECMWF.


Without going into detail, we can basically say that beyond day 6, we really don't have much of a clue where we are heading. The GFS and GFS Para charts suggest a fairly cool and changeable or perhaps unsettled period beyond 6 days, whereas the ECMWF brings in something much milder and much more settled. These major differences stand out like a sore thumb when you looks at the last 3 charts and will also be showing as major differences on the automated forecast websites and apps this morning.


Delving deeper into the model suites and their ensembles don't really help much in this model standoff. The GFS ensembles appear to offer support for their charts below, whereas the ECMWF ensemble mean, whilst not as mild and settled as the chart below, is still not really singing off the same hymn sheet as the GFS.


This is all very interesting from a model watching point of view, but not much help in determining conditions for the run up to Christmas.


To be continued...





Today's updates will appear here... snow forecast page expected to be updated first at 7.45am here...


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