For those that dare to dream of a White Christmas — grab a Mug, fill it, and let’s see if that dream will come true this year.

 

In our last report, we repeated one of the frequent attributes of wx models - that earlier prognostications often end up being correct.  On Dec 13 we wrote extensively about what could happen in the period from Christmas Eve through the following week — that a White Christmas was possible across most of the PNW (if you still have that email, read it again, as that will best explain the dynamics of what may happen later this week).  Now, what gives?

 

We have a better than 50% chance for a White Christmas here in the Willamette Valley, SW WA, Puget Sound environs, Lynden/Abbotsford, etc.  What we have coined ’The Juneau Low’ — our Christmas Present from Alaska —  will, by tomorrow Dec 21, begin to drop south along the Alaskan Panhandle & coastal BC to arrive in time for the big holiday.  The cold-centered Juneau Low, along with additional Lows will have enough trajectory over the eastern Pacific to pick up moisture and roll it onshore for surface snows, on and off, from Christmas Eve into early 2022.  Remember 2008?  Cold air aloft should keep the snow around between snow systems.  Some of the Lows will bring rain at first, then back to snow.

 

Cold Arctic air pooling over eastern Alaska/Yukon will also be shifting southeast, setting up the classic cold outflow from the Fraser Gap (and post-Christmas, the Columbia River Gorge).  Temperatures will plummet as the modified Arctic air gushes through the Gaps (Fraser Gap WINDS will be potentially damaging strong.  Prepare.)  We will get into the subfreezing temperature outlooks in a later report, for now, be sure to prep business & residential plumbing and thawed livestock water supplies, as this event could extend several days overall.  Travel will be challenging at all elevations.

 

How much snow?  Projections are always iffy, but for now, we will peg 2”-6” snow south of Salem, 6”-8” Salem north, similar amounts over much of western WA between Dec 24 & Jan 4.  Bellingham north will likely deal with snow drifts in the usual problem areas.  Again, all of this snow dream stuff could be just that, a dream.  However, there is less uncertainty as confidence is growing throughout wx forecasting industry in the PNW that The White is quite possible as the holidays get underway.

 

For now, the heavy rain (Mary’s River at Corvallis at flood stage) will cease as this day (Dec 20) progresses.  Tue should be mostly dry and relatively mild.  The next wet, breezy system is due sometime on Wed.  This one is the first of upcoming Lows spinning south along the Alaska Panhandle & BC coast.  The second one will combine with the 1st to become our Christmas Present, setting up the snowy forecast you just sipped through.

 

California will get in on the action, first as rain/wind storms, then the potential for low level snowfall as far south as the Bay Area.  News time, if this verifies.  The Sacramento Valley could get a hard frost if the sky clears during Christmas Weekend, and again in early January.  Bundle up; protect plumbing.

 

 

Colder weather is still on the way, although getting enough moisture to arrive at the same time may hold off a White Christmas this year.  That said, we still have the chance for some surface snow after Christmas.  Let’s explain.

 

This weekend.  A wet system will swing across the PNW, north-to-south, starting later tonight and Saturday into Sunday.  Breezy.  Vancouver Is & the Puget Sound will be first to get rain, then OR; freezing levels will rise ahead of the system.  Colder, dry air will be drawn into NW WA out of the Fraser Gap as an outflow begins to develop.  Not super cold.  A Low pressure trough west of the OR coast will spin some moisture over OR and SW WA Monday & Tue.  Snow showers will remain in the mountains.  That Low will remain off the coast next week, before slowing moving south to impact CA with plenty of rain & mountain snow.  Probably mostly dry and chilly Wed & Thu next week.

 

Christmas Eve, Day and weekend:  A relatively weak “Juneau Low" will move south from Juneau Alaska, setting up the chance for SNOW showers in the far north corner of WA late Christmas Day or night, as the Low will position just right to crank up quite a Fraser Gap outflow.  For the rest of us, it will be on the chilly side, but moisture will be limited, with temps generally remaining above freezing.  That Christmas Juneau Low will continue south, impacting CA by Sunday/Mon Dec 26,27.  (Please note: as discussed previously, this system has charted, at times, as strong and wet, with the potential for a snowy period across much of the PNW during the holiday weekend.  That was probably a model error, but model projections do shift, back and forth, so we’ll keep an eye on this next week.)

 

Post Christmas Uncertainty.  We have seen another Juneau Low on the extended-range wx charts for the week after Christmas, combined with a strong Fraser River outflow, it may set up a snowy pattern before the end of the year.  Several models are agreeing on a colder period after Christmas, but not firm enough to stick a forecast.  Anyway, that week may be rather cold, with frosty mornings if the sky clears in your location, or wet at times with snow in the foothills.  Stormy in CA.  Models also toy with a possible modified Arctic outbreak, too.  We are not confident about that at this time; maybe there will be less uncertainty for our next writing.  Keep your Mug handy.

 

 

 

A chilly, damp period is ahead, with some areas in the immediate future getting a sprinkle or two of The White.  What about your morn’n Mug location?  Let’s take a gander. This will be complicated, so stick with us, please.

 

Cool week ahead, with periods of showers & snow showers in the mountains.  For Tue & Wed this week, an approaching Low may draw colder air out from the Columbia River Gorge, and when combined with the coldest air aloft compared to the past few days, could bring on The White (1” or so) for a brief spell in portions of the Willamette Valley & higher chance around Hood River.  This system may also sprinkle The White around Chehalis, maybe north into portions of the SE area of the Puget Sound.  All iffy, and short-lived, but fun to witness, if verified.  Bellingham north Patrons should receive some precip, but whether or not stays as snow to the surface is iffy for now.  Any Patron around the PNW sipping their morn’n beverage above 500’ or so Tue & Wed should enjoy a short-shot of The White.  Mountain passes will be definitely requiring tire attention.

 

Thu into Fri should warm at the surface, moving chance for snowfall above 1,500-2,500 ft or so.  The next organized disturbance is modeled to arrive later Fri into Sat.  This will be rain at the surface, heavy snow in the mountains.  Sunday Dec 19 is trending generally dry & chilly; frost if the sky clears in your area.  

 

Christmas Week is beginning to look quite interesting.  Monday will usher in a chance for The White south of Salem before the surface air warms, as a system tracks off the coast of Oregon, drawing colder air in from the E/NE.  An outflow wind is possible from both Gaps - Fraser & Columbia River - but not super strong at this time (definitely could become an issues around Christmas - read on).  Tue & Wed Dec 21-22 are trending relatively DRY & chilly.  Thursday Dec 16 looks damp as a system moves in from the NW.  Not seeing snow risks quite yet, but Nature’s Christmas surprise may be just around corner.

 

Christmas Eve & Christmas Weekend:  the stage is being set - per model scenarios - for a very impactful WINTER STORM event (remember we talked about stages for snow last week?).  At that time, we had NOT been discussing an Arctic Outbreak-type of winter event, but now that is trending as POSSIBLE for the Big Holiday period.  Models hint of a High pressure Dome of 1044-1048 mb developing over the Yukon and moving south.  Should this actually take place, the pressure difference between interior BC and the Olympic Range could be huge - meaning powerful outflow winds from the Fraser River Gap.  (Outflow winds much colder than what we discussed on last Saturday’s Farm Show on KGMI 750 Talk Radio.)  Model runs suggest a rather deep Low pressure cell dropping south, right along the BC/WA coast, at the same time as that cold DOME figuratively drops into place.  As we mentioned in our last report, we all know the drill, if that happens.  Moisture, subfreezing outflow air - SNOW.  Back to the forecast —

 

Fri Dec 24.  Rain & wind increasing from Thu system as the surface Low moves south along the OR coast.  Air will turn snow-cold first over NW WA, Vancouver Is., SW BC as this event gets underway on Christmas Eve.  It is possible for the precip to turn from rain/showers north of Salem to all snow at some point overnight Thu into early Christmas Eve.  Odd movement of that Low - it may shift south near Brookings, then back north again - still off the coast - before literally “parking” itself just west of Vancouver Island.  Oh my, if this verifies, all that moisture will first turn back to rain at the surface, before swinging back to The White as Santa makes his jolly way across the rooftops.  Based on current model trends, SNOW is possible from Eugene all the way north into BC on Christmas Day.  Really?  Remember, just a crazy forecast for now, but seriously, we have not seen this pattern for Christmas on the model charts in years.  Ponder Point for sure.  Some solutions keep the NE cold air flow strong through that weekend; others place the coldest portions of that High Dome east of the Rockies, with enough drawn into the eastern basins of WA/OR to hold snow at the surface as possible after Christmas.

 

Monday Dec 27: another Low may follow a similar path as the Christmas Eve Low, and add to the moisture source, along with increasing E-NE outflow winds for more snow at low elevations, esp for NW WA.  Southerly winds should lift snow up off the surface over Willamette Valley, Portland at that time.  It may set up a FREEZING RAIN event for Salem north into Longview.  Double oh my, if this verifies.

 

NOTE: we do not take this kind of forecast lightly, as long-term Patrons understand.  This could ALL change back to ’normal’ mild Christmas weather, as you know, but it would be unwise NOT to heed what could be a reality, esp given the large numbers of folks traveling about the area during the big holiday.  Any amount of surface snow will challenge holiday travel.  We’ll monitor this closely the next several days.

 

 

 

Lots of impactful weather on the way.  Mug up.

 

A large pool of cold air, that we have been discussing here, is beginning to settle in over the eastern Pacific / Gulf of Alaska.  The resulting broad Low pressure trough will spawn several surface Lows over the next several days, most of which will track south towards CA and southern OR.  But first, a powerful storm will arrive this weekend.  WIND will be strong - steady at 35-45 mph in places, esp over western WA, 25-35 mph over western OR.  Gusts, both regions, will likely top 45-50+ mph - meaning power outages are probable.  Plan ahead, Patron!  Rain will be heavy, with anywhere from 1.5” - 3” possible in the lowlands between now and Monday afternoon.  SNOW in the mountains will be measured by the FEET.  A range of 2 ft - 6 ft of snow is being forecast, depending on elevation.  For Patrons traveling over the passes, beware, this is NOT a joke - have winter gear with you at all times.

 

Next week will remain on the damp side, with occasional low elevation snow (500-1,000 ft) or mixed snow/rain at the surface, esp north of Seattle.  More snow in the mountains.  Wed, Thu and/or Fri Dec 15-17 mornings could be ICY, if the sky clears in your area.  Do not rule out surface snow in the Bellingham/Lynden/Abbotsford areas anytime between thisSunday and the end of next week, as a weak outflow from the Fraser River Gap could enhance that chance.

 

Mixed chance for cold showers and dry conditions for the weekend of Dec 18,19.  It will continue on the cold side.  Models have differed on the solution for Christmas week, but for now, expect conditions to remain chilly, and maybe even turn colder because of increasing COLD outflow through the Gaps (Fraser & Columbia Rivers).  Another large cold air mass will reform over the eastern Pacific, setting up increase in offshore winds at the same time as Pacific moisture rolls in — yes, the classic set up for snow and/or freezing rain.  Either way, it looks WET most of that week.  Note that some solutions place a Low pressure cell just off the coast of WA, along with a dramatic pressure difference because of COLD High pressure over inland BC.  NW WA Patrons know the drill — strong outflow, freezing temps and moisture. 

 

Christmas Eve / Day:  trend is for chilly-to-cold weather to continue and for the chance for SNOW for NW WA & BC (see above).  For SW WA, OR and portions of northern CA, very wet period on Christmas Eve; damp Christmas Day.  Snow level around 1,500-2,500 ft.   Hood River area may have frozen precip issues.  Any mountain travel will require chains/snow tires.

 

In Summary: lots of rain, wind and feet of mountain snow on the way for all of the PNW; the chance for periods of surface snow or a rain/snow mix cannot be ruled out, esp for Patrons in the far NW corner of the region.  Yep, December.

 

 

Adjustment.  Modification.  Change.  That’s what you expect when your morn’n Mug is refilled, and you settle in to read the latest forecast outlook.  Well, here goes —

 

A dusting of snow did fall over the lowlands of NW WA last Friday, as the first tease of The White arrived up north.  Will the rest of us receive snow soon?  That’s part of the modification today.  Models are pooling the cold Alaskan air over the Gulf, but dropping it farther south, OFF THE COAST, rather than turning it inland over OR & WA.  At least that has been the model run trend the past 2 days.  However, overall pattern continues to follow our previous forecasts, with that ‘less change of snow at the surface’ adjustment.  

OK, the details.  Rain today will let up later today over OR, drying out up north, too.  It will be December cool on Tue.  The next system arrives from the NW before sunrise Wed, with rain, wind, mountain snow and cooler conditions by Thu.  Don’t rule out another shot of The White north of Seattle late Thu into Fri Dec 9,10 as the pattern is quite similar to last week.  Temps over Oregon will also trend lower, so foothill snow showers are definitely possible overnight Thu into Fri.  Patrons located above 800-1,200 ft could get decent dusting of snow, esp from Salem north.  Rain/snow mix at the surface remains possible south to Eugene.

 

The weekend of Dec 11,12:  A much stronger storm, from the NW, is charting to rapidly roll into the PNW overnight Fri the 10th.  This will be a WINDY storm, so hold on.  Right now, the chance for low elevation snow after the cold front passes has lessened, as the coldest pool of air will remain offshore (heading towards CA - see below).  Snow in the mountains above 2,000 ft will be HEAVY.  NE wind is possible by Mon Dec 13, but the air mass east of the mountains is not going to be super cold (as this is not a classic Arctic shot event).  That said, as moisture moves in from the west, snow showers or rain/snow mixed will definitely be teasing lots of folks west side of the mountains, esp above 800 - 1,000 ft.  As the colder air moves south off the coast, the NE winds will let up as the PNW will dry out a little before the next storm.  Frost & Icy roads possible Wed morning, Dec 15.  The rest of that week is charting as showery, with snow above 1,000 ft and snow/rain mixed down to surface in the heavier showers remaining possible.

 

A brisk NE-E wind will pick-up through the Fraser & Columbia Gaps through the weekend of Dec 18,19 - and continuing into the start of Christmas week.  This will not be a strong outflow, but definitely one to help keep the fog bank away.  

 

Christmas Week: early peek now indicating the chance for a quick shot of rain, Tue Dec 21, then drying for a couple of days.  Could be a bit warmer, too. 

 

California:  Your turn.  Lots of RAIN, wind and relatively low elevation snow is charting for several days - beginning overnight Sunday Dec 12.  Nearly continuous blustery, WET weather through the whole week of Dec 13-17, and portions of the following weekend.  Inverted umbrella time.  Localized flooding probable.  Heed Nat’l Wx Service alerts.

 

☕️ Second Cup:  it would only take a couple hundred mile shift in the cold air over the Gulf of Alaska & eastern Pacific to bring us valley snow between now and Dec 20.  Let’s see how all this develops.  There will be FEET of snow for the Ski Resorts, bringing smiles to all those that love the Slopes.