Chilly March Weather Ahead

March 3, 2010

We have 3 more days of mild weather on the way; soak it up since there will be a dramatic change on Sunday. Chillier temps and more “normal” March conditions begin on Sunday.

Models have come into much better agreement tonight that we get a fantastic spring-like day on Saturday. Offshore flow, no cloud cover, and 850mb temps up around +4 should push temps to 60 or a bit higher. We MIGHT see our warmest temp so far this season; and Pearson Airpark should get it’s first 70 degree temp of the season (inside joke for that warm ASOS sensor). That will make the big change Sunday and Monday even more noticeable for the general public.

A sharp cold front and then upper-level trough swings through Sunday afternoon and Monday. That drops 850mb temps down to the -5 to -8 degree range, depending on which model you follow. My forecast on the graphic is based on the GFS being a bit too cold in the end. A -8 will bring sticking snowfall down to sea level in early March at nighttime and with solid showers.  The 00z ECMWF just came in and it’s not quite as cold, but still a -5 deg at 850mb Monday afternoon.  We’re now into that time of the year that showers and sunbreaks combined with those cold temps will still mean highs well into the 40s, maybe even 50.

Of interest is also the following system Tuesday night and Wednesday.  With cold air in place snow levels could be quite low during that time.  This time of year everything would have to work out just right to get snow down to the hills around the metro area, but it’s happened many times in my 19 year career forecasting weather here in Portland.  But once again, it’s VERY tough to get sticking snow down in the lowest valleys where most of us live.  The latest measurable snowfall AT PDX is March 8th.  We’ve had traces later in the year than that.

Chief Meteorologist Mark Nelsen