It’s Snowing on the Blog

December 3, 2012

I’m not working today (a delayed weekend since I worked Saturday), but I see it’s “snowing” on the FOX12 Weather Blog.  That’s a WordPress thing, it’s supposed to put you in the Christmas mood.  It is NOT meant to be a secret message forecasting snow in the next few days.

I’m taking care of some outside duties since it’s mostly dry today, like fixing a gate and putting a good support up in my flimsy greenhouse so it can withstand much heavier snow this year (not a hidden forecast there either).  Last January, I came home at 2am to 9″ of heavy, wet snow.  The poor thing had a bow in the middle and appeared to be ready to snap.  I yanked the snow off (again at 2am) and it was fine.  I want to make sure that doesn’t happen again.  Better to do it now then in the middle of a snowstorm or deep freeze.  Seems like as I get older I get a little smarter at taking care of things ahead of time.  By the time I get to 80 I’ll have it all figured out right?

After checking the maps, I find two things:

1.  Tonight’s storm isn’t going to be TOO big of a deal; strong wind at the coast, gusty wind here in the Valleys, and lots of rain.  But no extremes of any of those.

2.  Interesting long range maps.  If one were following just text output, one might be led to believe “models are terrible and have no idea what’s going to happen beyond about Sunday”.  That’s partially true, but the trend appears to be for an upper level ridge to become established somewhere in the Eastern Pacific beyond that time.   In that position, a slight difference in location creates a big difference in day to day weather along the West Coast.  If the ridge is quite close to us, we stay mainly or all dry and near normal temp-wise.  If the ridge develops slightly farther west, one system after another (inside sliders?) dives down the back side of the ridge, giving us occasional rain and about average temps.  This 2nd setup sends real cold arctic air well to the east.  If the ridge is even farther west, cold troughs with low elevation snow and possibly arctic air could dive down into the Pacific Northwest on the back side of the ridge.  Right now, #2 appears most likely.  That’s what the ECWMF shows at 12z today.  Taking a look at its ensemble 850mb chart:

tseries_850t_000-360_Portland

you see the wide variation in temps over us.  Specifically look at the afternoon of the 12th; that’s Wednesday 9 days out where the 13DEC line is.  Out of the 51 ensemble members, some have 850mb temps up around +15 and the lowest is around -9.  That says to me some have the ridge directly over us and some have it much farther west (allowing cold air to come down from the north).  Some of the ensemble members imply a full on arctic blast late next week; look at the -17!  The GFS charts are similar, although none of them move the ridge as far to the west so no arctic blast on any of those.

What do I get from this?

1.  I don’t see a setup for snow to the lowest elevations in the next 7 days, but we don’t know beyond that.  850mb temps (-5 to -6) and thicknesses (522-526) sure support snow somewhere below 2,000′ late Friday and/or Saturday with a cool trough quickly moving through.  I’m not real confident that even I will see any at 1,000′ at home, but it WILL be the lowest we’ve seen snow so far this season for sure.

2. We could be heading into a real boring weather pattern in the 6-15 day period, or there could be a sudden shift to much colder during the period.  We don’t know that yet either.  Stay tuned!

3.  We are probably done with the storm lows coming in from the west and southwest for awhile once we get beyond tomorrow.  A shift toward cooler and at least slightly drier weather is on the way.

Chief Meteorologist Mark Nelsen

 


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