Wednesday, November 13, 2019

Slow Start to Winter Snow Season

After the extraordinary early snow during the first half of October, many skiers and snowboarders were greasing their skies and prepping their gear for an early start of the snow recreation season.

But alas, things did not work out that way.  Warmer temperatures followed and then starting October 25th, we entered a 14-day dry streak.  Most of the snow melted, leaving us worse than a year ago.  To illustrate, compare the snow depth today and one year ago (see below).  The north Cascades and southern BC had much more snow at higher elevations in 2018.


So what about this year?  We have had a "problem"--persistent high pressure over the northeast Pacific.   To illustrate here is the height anomaly (difference from normal) at 500 hPa (about 18,000 ft) for the past 30 days.  Red indicates higher heights (higher pressure/ridging), blue indicates troughing (lower than normal heights).  A strong persistent pattern that explains the dryness and warmth of the West Coast and the cool/wet weather of the eastern US, since ridging brings drying and troughing, the opposite.

The forecast for the next five days for the same level?  A big ridge over the west coast (the shading is the anomaly, with orange being higher than normal).  This is a wetter pattern, but relatively warm.  Not good for snow.

The latest 7-day accumulated snow forecast from the UW system provides some snow at the highest elevations over the north Cascades, but even there only 6-12 inches.

Strangely enough the persistence of this ridge could be a good thing for snow later in the season--if the ridge moves back towards the west, we might be open to a trough coming from the north, like last February.  We will see. 

The media has been full of winter weather forecasts, the skill of which is marginal at best.