Still Looking Chilly

March 5, 2010

A busy afternoon/evening; Steph is off today so I got all the shows.  It makes for a long day but it was nice to have some good changes to forecast and track.  By that I’m referring to the warm weather tomorrow and the cold weather early next week.

I don’t see anything significantly different from last night at this time.  IF we had significant moisture around either early Monday morning or early Tuesday morning I could easily see us getting snow down to the city.  But I sure don’t see that.  Our RPM is really pathetic on moisture Monday morning and the GFS doesn’t look wet early Tuesday morning.  After that temps warm and our brief flirtation with low snow levels is over for the week.   Now I admit that we could get some nice convective showers moving in from the northwest Monday afternoon.  That may give us the most meteorological fun.  They would probably contain hail and could even change to all snow, especially after 5pm in the lowest elevations.

Due to the lack of any good vorticity maximum, surface low, or anything “organized-looking”, I’m not too excited about even more than a trace below about 1,500′.  It could end up being a real waste of a very cold polar maritime airmass.  In the past (2006 anyone???) we’ve seen vigorous and heavy showers with a similar setup.   The big difference then was strong westerly flow up above with lots of moisture following a cold front.  This time a surface ridge is building in ahead of the next system and the cold trough is passing through quickly instead of sitting over us for 2 days.

So I’ll do some forecast percentages:

100% chance of at least a dusting to 1,500′

50% chance of a widespread dusting to 1,000′

30% chance of widespread dusting below 500′ in the Portland Metro area.

5% chance of no school Monday morning at more than 1-2 local school districts (do your homework!)

30% chance of a hard freeze; less than 25 degrees in Hillsboro or 28 @ PDX  (only chance is Tuesday morning).

Chief Meteorologist Mark Nelsen