Tricky Weekend Forecast

March 13, 2014

I admit my blogging has slowed down dramatically the past couple of weeks; that’s because the weather itself is quite slow and I don’t feel as inspired.  Sorry, that’s how it works.

But this weekend’s forecast has been interesting to watch.  We kept showers in Sunday’s forecast all this week based on the ECMWF model.  The ECMWF has been steadfastly sticking to a rainy Sunday with a system crashing the mild ridge much more quickly than the GFS.  Here is this morning’s forecast for Sunday at 11am:

ecmwf_slp_precip_nw_14

Then in the past 24 hours the GFS has now pretty much come around to that idea…no big surprise that it’s playing catch-up to the ECMWF once again.    So here’s our latest forecast for the Shamrock Run early Sunday morning:

MarkShamrockRun

Now you’ll notice areas to the south and east of a Portland to Lincoln City line could stay dry for a good part of Sunday.  So the forecast is still not set in stone; a slight northward shift would mean a dry Sunday morning here in Portland…Stay Tuned!

There is one interesting tidbit that I first noticed on the ECMWF and now I see on the WRF-GFS.  On Sunday evening/night it looks like we may get a rare “Anafront”.  That’s when most of the precipitation occurs just behind the cold front as opposed to ahead of it.  There is a sharp wind shift and a dramatic drop in snow level.  The WRF-GFS shows the temperature in Portland dropping from 55 to 40 in just a few hours with the wind shift.  That would imply snow could stick down below 2,000 or 1,500′.  It also generates 8-12″ along the west slopes of the Cascades.  This may be the heaviest snowfall of the “winter” around 2,000′ other than what we saw during the 2nd arctic blast in February.  Something to watch the next day or so.

Other than that, real slow weather continues next week, the 3rd week of March.  Milder midweek with weak ridging, then a colder trough again near the end of next week.

Chief Meteorologist Mark Nelsen