Weekend Update

February 15, 2013

Friday was a spectacular taste of “False Spring” with temps up to 61 here in Portland and as high as 63 in Hillsboro.  A perfect combination of a mild atmosphere overhead and dry easterly wind plus sunshine almost the entire day.

Totally different tomorrow with a cold front passing overhead around daybreak.  Not much moisture with this, and that’s the story for this weekend.

We’ll see a mix of sun and clouds with occasional light showers over the weekend, but it shouldn’t be a “gloomy weekend” by any means.  Did I say light showers?  Check out the 00z RPM:

RPM_RAIN_NWOREGON

Only a few hundredths of an inch through Monday afternoon, most of that tomorrow morning.

The big picture over the next week looks like this:

MarkJetStream

Upper ridging backs offshore a bit more, allowing colder systems to ride down the back side of the ridge along the West Coast.  As I first mentioned earlier this week, there is a pronounced split in these systems with most energy going to our south.  Remember that at one point it appeared we could see low elevation snow Tuesday morning?  That’s gone and we’ll be lucky to see much of ANY precipitation that day, plus models have warmed up a bit too.  A couple more splitty systems the 2nd half of the week and pretty soon the entire 7 day rainfall total looks like what you see on the graphic.

Now it will be chilly the next week or so…850mb temps are pretty much between -3 and -6 through the end of next week; that equates to a snow level between 1,500′ and 2,500′.

How about the 2nd period that models have been hinting we might see lower snow levels?  Right around the 24th-25th?

The ECMWF was still a little cooler around that period, but it’s warmed slightly the past day or two.  In fact look at how consistently cool it is through the entire 10-15 day period on the ensemble chart!

tseries_850t_000-360_Portland

But no sign of really cold air to get snow to the lowest elevations.

Here is the brand new 00z GFS ensemble chart:

tseries_850t_000-384_Portland

It is similar through about Monday the 25th, then a slight rise on the ensemble mean temps.  No sign of a snow pattern there.  The upper level flow basically just flattens out quite a bit between days 10-15.

So these are the highlights

  1. The next week or more will be very chilly, but not a stormy or very wet pattern.  Plenty of sunny periods mixed in with clouds and showers at times
  2. We aren’t going to see an arctic blast this winter, we have run out of time
  3. No sign of snow at the lowest elevations through at least the next week.

Chief Meteorologist Mark Nelsen


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