Uncertainty

Tonight light snow and strong NE winds has spread from the Bellingham area, across the San Juans, to lower Vancouver Island....and the next to be hit is the northern Olympic peninsula. The model forecasts were quite good for this. Here is the current surface observations...you can clearly see the NE winds exiting the Fraser.
Saturday and Sunday is really going to be pretty dull around here...not much action, snow-wise or otherwise. And we know that cold is coming and Tuesday morning will be cold enough to produce a hard freeze. The question is snow late Sunday and Monday.

Until this morning, the models showed too little moisture on Monday for any real snow. But now there is some disagreement. The NAM model has a much stronger upper level wave moving down the northerly flow along the West Coast, compared to the GFS model (which is usually the better one). One has a few light snow showers, the other more serious snow. I would generally bet on the GFS model...but we have time to see which solution dominates. Want to see the difference? Here are the two:


Pretty subtle? But a world of difference. There disturbances are forming over the arctic where we don't have that much data. Sometimes we have to live with uncertainty in forecasts and this is one of those times. I expect by Sunday we will know what will happen...enough time to prepare. And I will start using and showing you some of new high-tech tools for dealing with uncertainty...ensembles forecasts with statistical postprocessing!