Challenging Snow Forecasts

Quite a tough forecast the next 7 days!  First we have to figure out how low the snow level goes the next 2-3 days and how much falls where, then it’s on to the possibility of more significant snowfall early next week.

You’ve seen my thoughts in the previous post.  Lots of onshore flow and brisk south/southwest wind continues at the lowest elevations through Thursday night.  My gut forecast instinct is that means nothing other than a dusting possible in isolated low elevation spots.  I think our RPM model (and probably the UW NAM model again…it’s a real pain) are too agressive with overnight cooling both tomorrow night and Thursday night.  They both show temps down around freezing even at the lowest elevations both nights.  Sure, that’ll happen in isolated spots (Forest Grove?) if the south wind dies down, but I find that really hard to believe for most of us in the Valleys.  That’s where those models both combine the overnight temps and continuing showers into several inches of snowfall.  So I’m discounting that in my forecast (the previous post).

Drying commences on Friday (especially the GFS, it takes all the moisture south), and that continues through Saturday night.

It seems to me the GFS is trending a bit more towards the ECMWF on the Sunday-Monday system, swinging far more energy offshore before bringing it inland on Monday.  At least that’s the GFS trend the last 3 model runs.  But as we’ve seen in the recent past, (November and again in early January), those small details on the global models have huge effects down here near sea level in the Pacific Northwest where we live in such a borderline snow climate.    The ECMWF (Sun-Mon) is another borderline snow situation, in fact I don’t see any sticking snow in the Valleys Sunday or Sunday evening on that model.  The GFS (as of 00z) is slightly colder and looks a bit better for SOME snow Sunday night or Monday morning, but this could easily just be a “dusting” event again.  Still too far away to know.  I see both models are drier after that time.  Regardless, as of now I don’t see a great setup for a major snowstorm (3″+).  But even that could still change.

Chief Meteorologist Mark Nelsen