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8pm Thursday...

Our cold season so far (November through February) has been warmer and drier than average.  November was near normal, but then very mild December through January.

Winter So Far Recap

Of course November was excessively dry, and drier than average conditions continued through December.  Now it’s makeup time.  Plenty of rain this month and lots more coming the last 8 days of January

Winter So Far Recap2

This winter (so far!) has been similar to last year for meteorologists…one of the most boring on record.  I do a winter recap presentation for our local Oregon AMS Chapter each fall; keeping a file of important weather pics or events.  I just checked that file; some pics of vehicles stuck in tumbleweeds, a bomb cyclone into southern Oregon, and low snowpack images.  Oh, a little EF-0 tornado in Manzanita too.  That’s it!   No real flooding, lowland snow, valley windstorms, and just barely a coastal windstorm.

Winter So Far Intro It’s also interesting that our coldest temperature of winter was in November this year…again so far.  26 degrees the last two mornings of November during that cold snap around Thanksgiving.  Salem hit 20 those mornings, and a 19 at Hillsboro.

Winter Coldest Day Each Year

You may remember through much of October through early January we saw either a weak jet stream, upper-level ridging, or a split flow with weather systems going into California.  But in the past week a more typical wet westerly jet stream has been sending weather systems into the Pacific Northwest.  It’s a mild westerly flow with occasional rain at the ski areas mixed with snowy periods.  Plenty of rain falls in the valleys too.  Take a look at the rain forecast from the ECMWF model for the next 6 days.  2-3″ in the valleys and up to 8″ in mountains (some of that will fall as snow).  You can see the below average upper-level heights over us next Monday…

500_monday

Then weak ridging with a possible atmospheric river setup around next Thursday

500_thursday

We’re looking at the ECMWF ensembles from last night; a compilation of many different runs of one model.

It appears there will be a change right around Superbowl Sunday.  All models show at least a brief colder period with an upper-level trough dropping through the region.  Here’s that Sunday…this is 10 days out in time

500_sunday

Just for fun; you can see four days later the ridging pops back up closer to us.  This is two weeks from now.

500_thu_6th

So based on this and other model info available right now:

  1. The last 8 days of January will feature the weather we have right now: Mild, wet, & occasionally windy
  2. There will not be any significant freezing the rest of the month
  3. Expect the Cascade snowpack to increase in depth; a mix of more rain + snow
  4. No sign of lowland snow or freezing rain through the end of the month, but maybe a brief flirtation with low elevation “onshore flow” type snow in 11-13 days?  Just a small possibility now.

What about that cold trough in early February around Superbowl Sunday and the following Monday/Tuesday?  A few of the ECMWF ensemble members think it could be a “wet snow showers” setup.  I chose Aurora as a location since the PDX site tends to have resolution issues with SW Washington Cascades so close.

ecmwf-ensemble-KUAO-indiv_snow_24-9780800

CMC (Canadian) ensembles have fewer members with a wet snow chance

cmc-ensemble-all-KUAO-indiv_snow-9780800

That’s it for now…enjoy the rain and stay dry!

Chief Meteorologist Mark Nelsen

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