Good morning folks! Wow…we have an interesting taste of early winter on the way for the Pacific Northwest this week.  Snow levels have dropped below passes this morning, a sign of the cold air moving in.  And even colder air is expected by Thanksgiving Day.   Fortunately, there won’t be much moisture in Portland after today Monday, which means that we should avoid a snowy/icy scenario as we prepare for the holiday weekend.

But in Southern Oregon and Northern California, it’s a different ball game.  Over the past couple days a “bomb cyclone ” has popped up on the maps for tomorrow Tuesday.  That’s a low pressure system that strengthens extremely fast.  In this case, a 1004mb depression over the ocean will deepen to 974mb in just 12 hours!  It is headed for the southern Oregon coast, between Bandon and Brookings.  Precip and wind maps for tomorrow afternoon, courtesy of TropicalTidbits.com:

Those are some 50-70 knot winds out over the coastal ocean (55-80 mph)!  For places over land, though, the big issue will be snow.  Any elevated terrain over SW Oregon, including Siskiyou Summit, will be looking at several inches to a foot or more late Tuesday into early Wednesday.  Not good if your travel plans take you south…be prepared to delay until Wed. night or even Thursday if needed.  Courtesy of WRF-GFS, last night’s snow forecast:

There will also be lots of snow over Eastern Oregon, aided by upsloping NNE winds as the cold air moves in. But Portland should be mostly dry by Tuesday afternoon.  Maybe a few snow showers develop in the central Gorge, but that’s a big maybe.

Wednesday through Friday should be clear, cold and dry across most of the region, with decreasing snow showers in Eastern Oregon.  This will probably be the coldest Thanksgiving Day in our region, so far in the 21st century.  Highs only in the 30s most places, and lows in the teens and 20s.

One thing I’m noticing on the maps for late Saturday and Sunday:  Another weaker low tries to sneak up from the southwest on the 12z GFS.  This is still too far away to make a call.  But it might give us a chance at least for some snow or ice as the holiday weekend comes to a close.  We’ve seen this scenario develop before with southerly lows, most notoriously in February 2014.

Other than a slight chance of winter action Sunday, we’re looking to be mostly dry this weekend and much of next week, albeit cold.  That means the first two months of our rainy season- October and November- will both end up extremely dry in Portland and NW Oregon. Kind of a dud for what was slated to be an active storm season…but hey, that’s jet stream amplification for ya! Thankfully we still have four months to see an active storm track develop.

• Stay warm this week.  HAPPY THANKSGIVING!