An Optimistic Snow Forecast

I knew that headline would get your attention, but sadly it doesn't apply to northern Utah, but instead the European Alps near and south of the Alpine crest.  

The large-scale setup is related to the high-amplitude flow pattern that is dominating the northern hemisphere.  Over the next couple of days, this pattern features an amplifying ridge over the north Atlantic and a deepening trough over western Europe, as depicted in the GFS dynamic tropopause (upper-level) flow forecast for 1200 UTC Saturday 5 December.  

This is a very slow moving pattern that leads to intense water-vapor transport toward the Alps from the Mediterranean and Adriatic Seas.  Such vapor transport is strongly influenced by flow interactions not only with the Alps, but also with the Apennines of Italy and the Dinaric Alps of Croatia and the Balkan States.  This can be seen in the GFS forecasts of 925-mb (roughly 750 meters above sea level) wind, moisture transport (color contours), and 3-hour accumulated precipitation (color fill).  At 1200 UTC 4 December, strong moisture transport is occurring from the south-southwest over the Gulf of Genoa and, due to flow blocking by the Alps, up the Po Valley.  This often leads to heavy precipitation in the region around Lago Maggiore region of northeast Italy and southern Switzerland (white dot).  

A day later, at 1200 UTC 5 December, as the storm shifts eastward, south-southeasterly flow up the Adriatic leads to strong moisture transport toward the Southern Limestone Alps, including the Adamello Alps (blue circle), Ortler Alps (orange circle), and Dolomites (white circle).  These areas will see very heavy precipitation.  

A meteogram for the Dolomites near Canazei shows 184 mm (7.2 inches) of precipitation by 0600 UTC Sunday, most falling since 1200 UTC Friday, with an increase in snow depth of over a meter.  

Enjoy watching a storm in another part of the world if we can't have one here.