Small but coldest airmass in 20 years moves towards Alaska, likely reinforcing the Arctic Ocean gyre High

~Optically significant event of very cold stable air mass centered in the West of Canadian Arctic Archipelago was made to move by warm cyclone interaction.

~Most significant coldest upper air measured by vertical sun disk method in 20 years, had remarkably stable properties lasting at least 4 weeks. 

       A steady area of cold air kept  sun disks shrunken  for nearly a month, but not near the surface,  this particular nature of steadiness is interesting,  but the level of cold was not seen since 2002,
which was several years after massive 1998 El-Nino,  now likewise several years after massive El-Nino peaking end of 2015,  we see the result of steady La-Nina influence of less clouds,  particularly away from influx of  Northern moisture from frequent North Atlantic warm cyclone injections,  the dry air it seems,  survived mainly to the West and South of central CAA.   The West CTNP  (Cold Temperature North Pole) vortex  just recently got displaced Westwards towards Alaska:

We see CAA very cold vortex, a zone of clear air, been assaulted by massive cyclone from the Southwest,  in fact the CTNP vortex dragged the cyclone Northeastwards,  but it is as significantly deeply cold  as any in the distant past,   what we literally see is this cold air moving westwards towards Alaska in less than a day.   CMC IR animation above comprises pictures from April 18 to Early April 20 2018.  

  Although the cold zone was moving Westward,  surface temperatures did not seem to reflect so,  in particular because of clear air sun warming as the day progressed from 12 18 00 and 06 UTC , seen here as the cyclone progressed Northwards (extreme right).  In addition this cold zone had strange features of sun disks more compressed in the upper atmosphere rather than near the horizon,  this cold atmospheric area had a complex upper air profile, more adiabatic near the surface, with very cold temperatures  likely above 850 mb.   Next day in morning we see where it moved has already  changed the weather  :

The entire area surface air has cooled further,  CMC April 20 2018  12z.   But rather the larger influence of a stable mass of cold atmosphere would be with consolidation of the Gyre High:

   CMC 72 hours forecast based April 20 2018 at 00z.    This forecast increased the anticyclone strength a bit ,  perhaps off by 5 to 10 mb,  since the cold zone observed optically was never really measured by upper air soundings,  it is a known uncertain player in a general circulation pattern really significant for sea ice, the Arctic Ocean Gyre High is a major contributor in reducing sea ice volume especially during spring and summer.  The peculiar stable nature of the observed cold zone should  not be underestimated,    this gyre High may last quite a long time.  WD April 20, 2018