Monday December Two

Chilly morning, so refill that Mug with your fav hot beverage and check out the latest outlook.  

Dry chilly conditions should hold until later this week, then the first chance for some precip in Dec is possible, as well as a short-shot of warmer temperatures. Currently, looks like the Puget Sound region has a higher chance for showers Thu & Fri vs the rest of the PNW, but either way, the system will be blasé.  Again, best part will be warmer temps, given the southerly flow.

The coming weekend has trended damp overnight Fri into Sat, with cooler temps and drier air moving in on Sunday as a cold front drops to the SE..  Rather wet for our Vancouver Island Patrons, and those farther north along the BC coast.  Fairly standard early December weekend. 

Next week we see a return to cool, dry conditions Mon & most of Tue.  Overnight Tue & early Wed a weak system may provide some minimal precipitation; Idaho likely to get good dose of rain on Wed Dec 4.  Regionally, cooler temps will prevail Thu & Fri (the 13th) as the coldest air of the season settles east of the Cascades and over the Continental Divide.  (Not much pressure difference between east & west sides is charting on the models, so don’t expect an east wind event.)  However, the atmospheric adjustments for December 2024 may begin to set the stage for a COLD second half of Month Twelve.  Read on.

RAIN will return with a notable Pacific storm over the weekend of Dec 14,15.  VERY cold air mass will flow down over the Gulf of Alaska from the interior, setting up the classic cold vs warm air battle - which equates to moderate-to-heavy rain, along with plenty of snow in the mountains.  In fact, we see the potential for LOW elevation SNOW around the PNW late that weekend.  We’ll monitor this closely.  We also see potential for low elevation snow or rain/snow mixed on Mon Dec 16.  

The week of Dec 16-20 is trending VERY WET early in the week.  There have been some model solutions bringing our first Arctic Outbreak into the region that week, but for now, that has changed to the more normal heavy rain, plenty of mtn snow outlook.  

Again, the overall pattern may shift into a colder one for the second half of the month.  Will snow be in the works for Christmas?  Patience.

Black Friday 2024

Given the holiday, we’ll keep this short.  The PNW will be dominated.   Say what?  ☕️

Yep, dominated by High pressure.  A large, stable High pressure ridge will block all threats for precipitation around the entire PNW through roughly Sat night Dec 7.  After that, no more precip until Fri the 13th.  (Exception: the BC coast & Northern Vancouver Island will be quite wet!)  The moisture arriving late Pearl Harbor Day - Dec 7 - will be targeted mostly over the Puget Sound north. 

Generally DRY until the middle of December.  The change back to the normally cold, wet, snowy December weather will begin the weekend of Dec 14,15.  Until then, expect periods of fog & afternoon sunshine probable. 

Thanksgiving week already.  Let’s get right to the outlook.   ☕️Mug is full.

In comparison with many Thanksgiving weeks, this one will be generally pleasant and calm across the West.  Some wx issues face those traveling to the east, as the first, large-scale blast of cold Canadian air drops across much of the eastern half of the Nation.  The PNW will slowly dry-down early this week, then present a calm holiday weekend for all.  Fog possible in the usual locations.

Post-Thanksgiving week - December 2 through Fri the 6th - looks dry, except for the far NW corner of WA & Vancouver Island, southern BC, where it will turn quite WET.  Moderate-to-heavy rainfall is charting for coastal BC & the Alaskan Panhandle.  Windy, too.  For the rest of the PNW, we can expect some showers over the Puget Sound region; generally dry elsewhere.

The weekend of Dec 7,8 trends dry early Sat, turning damp overnight as a weak cold front zooms past the region.  Afterward, it could be dry again for another few days.  Models have toyed with a cold wx outbreak, but that seems to be an outlier solution that some are grabbing onto.  A Yukon Dome of 1040 mb does develop during the next couple of weeks, but drifts in the normal pattern over the lower 48, east of the Rockies.  We always monitor closely.  We will provide an update on Black Friday.

Around the PNW, lots of clean-up and power restoration in progress after the big storm this week.  What weather-card does the end of November hold?  Let’s take a look.

First of all, blustery & damp today, as the last in the current series of strong storms spins north a few hundreds miles offshore.  The atmosphere will ‘calm down’ throughout the weekend, with occasional showers and gradually cooling temperatures - a calming atmosphere, if you will, has we enter the first big holiday week of the season.  An east wind will blow down the Fraser Gap, but nothing of significance, other than a chill factor.

A stable, cool air mass will reside over the PNW next week.  Morning fog possible in the usual locations; frost probable, if the sky clears in your location, esp in the higher elevations & east of the Cascades.  Good news is that there is NO LONGER the chance for powerful east wind outflow from the Fraser Gap or Columbia Gorge during the holiday.  Models now keep the atmosphere rather tranquil for late November.  Most of the ‘winter wx’ will be in play across the plains and eastern half of the nation.  Generally DRY for the extended Thanksgiving holiday, excluding the last day.

The next chance for rain around the PNW is charting for Sunday, the 1st day of December.  Rain will advance north-to-south, covering nearly all of the PNW (including northern CA) by the afternoon.  Nothing heavy, no wind event - just a calm, cool rain.

Mon through Fri, Dec 2-6.  Rain will let up late Mon in most locations, before starting back up again on Tue.  A stronger system will dump lots of precipitation over Vancouver Island & the northern 2/3 of western WA Tue through Wed.  A couple inches possible, with most of OR only getting a small ‘clip’ of rain from that 2 day pattern.  Models continue heavy rainfall over northern Vancouver Island for the balance of the week, as the train of moisture lifts a bit farther north, compared to Mon/Tue.  Showers possible for the Puget Sound, but dry elsewhere around the region.

The weekend of Dec 7,8 is trending DRY & rather mild for early December.  

Upper-level pattern looks to have shifted away from any cold outbreaks in early December.  Let’s see if that holds.  Change is always expected.  

Where do we start?  Wow, lots of impactful weather about to hit the PNW and California.  Extra-size your morning beverage, this will take some time to absorb.  It is important.  Ready?

Probably best to break this monster forecast into 2 Parts, as each piece could have ramifications on life & property, depending on your location.  (Remember Patron, our forecast discussions cover BC, WA, OR, CA and ID, so while your specific area may not have a serious impact, another area in our region very well could.)  Enough said.

—> Biggest adjustment since our Saturday Special Statement is that the heaviest rainfall, and thus risk for MAJOR flooding, has been shifted, by the models, farther south into Northern CA, generally north of the Bay area up into the southern margin of OR.  That’s NOT to say the rest of the region will escape lots of rain and localized flooding of small creeks and urban area (leaf blockage of storm drains).  

Kuril Islands Storm - This system is continuing to develop, with the potential for center Low pressure to rapidly fall (hence the term ‘bomb cyclone' used by some) to 941-950 mb by the time it is a few hundred miles west of Vancouver Island.  That is equivalent to a major hurricane.  WINDS will be strong from the EAST, as the storm approaches, but it will NOT make landfall (thank goodness the High pressure Dome will block further eastward movement).  Interestingly, the actual Low will rotate offshore and spin farther West before returning as a weak Low to northern CA a week from now.  

WINDS.  Strong winds along the west coast from Bay area north to BC; inland S winds could gust to 40 mph.  It could be the powerful EAST winds, pushing out from that formerly Yukon Dome as it settles to our east, that could have impact.  The Gaps - Fraser & Columbia Gorge - will be very windy.  Even Cascade passes will be very windy.  Also, as the S wind clashes with the E wind along the western edge of the Cascades, winds will be intense.  Falling trees possible given saturated soils.  Power outages, too.

RAIN.  As noted above, inches of precip is likely for all locations west of the mountains between late Tue and Saturday.  Northern CA could have MAJOR ISSUES with flooding, as models indicated 7”-9” in the period.  To quote Behringer, Nat’l Wx Service, San Francsico, “getting caught up on whether a storm is a ‘bomb cyclone’ or not does not effectively communicate the associated impacts on life and property”.  OR & WA may have dodged the high risk of major flooding this time.  Generally, rain should let up a bit on Fri, except for northern CA.  The weekend is trending damp on Saturday, turning cooler & drier on Sunday.  

COASTAL EROSION.  Beach communities will experience lots of high wave action and beach erosion.  Patrons in these locations must remain alert.

Thanksgiving Week is trending drier but NOTABLY COLDER.  Yukon Domes will continue to have influence on PNW wx conditions, as a ’second’ Dome moves SE out of Canada.  The air will dry beginning Sunday, and an East wind will pick up.  Indications are that by Tue, wind will rush down the Fraser Gap (not severe!), cooling the Puget Sound region.  Not so much out of the Columbia yet.  A weak system from the west could bring rain onshore overnight Tue.  Will it be cold enough for rain/snow mixed at the surface?  We’ll see.  Anyway, on Wednesday, showers will begin to diminish late day, and the Fraser Gap winds will return - this time building into a major wind event for the northern portion of the Puget Sound.  Rain continues over western OR overnight Wed into Thanksgiving Day.

Thanksgiving.  Moderate rain all day in OR, heavy rain all day in CA, and turning COLDER in the Puget Sound area, with the Fraser Gap wind howling.  In fact, Patrons around Lynden, etc should prep for potentially damaging winds & possible power outages overnight Thanksgiving into Black Friday.  We’ll update this, of course.

Strong east winds out of the Columbia Gorge Sunday Dec 1st.  Another very WET week will follow Thanksgiving Weekend.  This time we may NOT dodge the flood-bullet.  More on that in the next report.  

Bottom line:  the blocking High pressure ridge inland is literally saving the PNW from an extremely dangerous wind event.  Potential barometric pressures - in what we have coined the “Kuril Islands Storm” - are way below that of the Columbus Day storm in 1962.  While the storm will not get too close to our coasts, it will have impact, so please heed all the watches and warnings issued by the Nat’l Wx Service.