Winter Outlook 2020 - 2021

By Rod Hill on 2020-10-23


Rod Hill’s 2020-2021 Winter Outlook



NOAA projects a 75% likelihood that La Nina conditions will remain in place through the entirety of the winter season.  The projection is for Pacific waters in the equatorial region off the coast of South America to average -1 to -1.4 degrees Celsius below climate average which would classify as a moderate La Nina.  La Nina conditions are the basis from my “active” winter outlook. 


Looking at La Nina years as a whole dating back to 1950 and especially zeroing in on moderate episodes the forecast headline for this coming winter is that a dry season would be highly unlikely. 

 

Here is my outlook:




The highest confidence of the outlook is the call for heavier than normal rainfall from November through March. Having 6” of November rain or higher will be key to a wet water year.  My projection would lead to a 40” total water year or higher for the 2020-2021 season.  (Normal at PDX is 36.03”)




The valley temperature outlook calls for a warmer than normal season overall, largely due to mild overnight temperatures being produced by an active, wet westerly flow pattern.  I am watching the possibility of a dry streak in December that would lead to freezing overnight temperatures.  February appears to be the best chance of seeing an Arctic air mass with much below normal temperatures.




Of course the “biggie” when it comes to winter projections is the valley snow forecast.  La Nina years offer the highest probability to see valley snowfall.  The snowy December of 2008 was a weak La Nina season, which stands in slight contrast to the expected moderate La Nina this winter. 

December of 2008 saw 19” of snowfall, a record Christmas Day depth of 10” on the ground and 24” for the winter season!  While some snow is likely this season, the biggest winter snows for the valley since 2000 have come during weak La Nina and Neutral years.  This year is expected to be a moderate La Nina season which have produced a season range from 3” to 22” dating back to 1950.  Meaning we have always had at least some snow and the chance of a big one is elevated. 



Here are the final headlines for my Portland Winter 2020-2021 Outlook:



_________________________________________________________


The Mt. Hood snowpack is also of particular interest and the news is good as La Nina seasons typically bring good to great seasons and rarely disappoint.



I chose not to include valley windstorms in this outlook.  It is not uncommon in any winter season to have several 50 mph wind gusts events, including east gorge winds.  The Columbus Day storm of 1962 was a Neutral Enso Year.  

Here is hoping this winter brings you the weather you love!

Meteorologist Rod Hill



____________________________________________________


My report card from last winter was not good.  

 

1.  I projected near normal Mt Hood snow - turned out to be much drier than normal.  (I will email the exact figure to you this afternoon)

 

2.  I projected a good chance to see of one 8” snow event in Portland.  PDX had 1/2” in 

     the month of March.  This was a big fail on my part. 

 

3.  My rainfall forecast was good!   I projected a Nov - March total of 18.39” and the season total

     was 17.47”.

 

*I do believe the lack of cold weather and snow was in large part due to the Pacific “blob” of warm waters that formed off of the Northwest coastline last winter.  January saw the 6th warmest PDX high temp. average in the record book.  No signs of the so-called warm blob this winter.  The Gulf of Alaska should be wide open to bring an active winter season.