An Arctic Event Coming?

Will another modified Arctic outbreak arrive as the month ends?  Go refill that Mug and get back here, will ya?

This week will be dry across the PNW, with fog at times, along with a few peeks at the sun.  It will remain on the chilly side, as colder air is trapped at the surface, with a ‘warmer blanket’ over the top.  Accordingly, stagnant air will become an issue as the week progresses.  Indications are for the Pacific High to shift a bit farther west by week’s end, opening the door for a colder, continental air mass to push in from the north.  Indeed - as we suspected 10 days ago - a Yukon Dome of High pressure exceeding 1040 mb is charted to move south along the Canadian Coastal Mountains & Canadian Cascades, setting up a renewed chance for a modified Arctic Event as January ends.  That said, expect the leading edge of that cold air mass to move into position by Friday.  A very weak Low may be pinched between ’the two highs’ we noted last time, so a shower or two is possible anywhere in the PNW as the week ends.  

By the weekend, a COLD Fraser Gap WIND should increase on Saturday the 28th; east winds out of the Columbia Gorge will ’turn on’ later in the weekend.  The air mass, which will have Arctic origins as a 1040-1042 mb High, will press south - centered over the Continental Divide - and should be large/heavy enough to push cold air across the eastern basins of the PNW, through the “gaps” into western valleys.  Early yet for forecast precise low temps, but it will be the coldest air mass since the Dec event; it may end up colder.

The final two days of January will start the week with cold air in place.  No wet system is charting to arrive just yet, so freezing FOG will be quite possible in the usual foggy-bottom locations.  

Models do vary quite a bit as to the start of February.  Some suggest that a cold, wet system will track SOUTH along the BC coast, bringing cold-core moisture in over the cold air at the surface - which would fall as snow or ice pellets.  This would be on Wed Feb 1, or that night; with just plain SNOW on Ground Hog Day.  Other solutions bring moderate precip in from the WEST, which would trigger a freezing rain event during the week.  Either way, Patrons should be prepared for another winter event that could hinder travel/outdoor plans.  

Bear in mind that, while the above scenario is probable, the timing of arrival for the colder air can have a 12-24 hr swing.  That is normal when these events threaten.  Or, it can simply not happen at all.  We have seen this on the charts for several model runs, so this forecast is warranted.