Our crazy warm November is running at nearly 4 degrees above normal mean temperature as the final day of the month arrives. Depending on today’s numbers, November 2021 may crack the top 5 for warmest November on record.
The last few days have seen three consecutive record highs tied or broken at PDX:
Nov 27 - Record high of 63 degrees
Nov 28 - Record high of 63 degrees
Nov 29 - Record high of 58 degrees
Despite mild overnight lows near 50 degrees, no high-low records have been reached.
Total November rainfall at PDX this month sits at6.41 inches, well above the monthly norm of
5.45 inches. It may sound crazy, but rain totals would need to top 9 inches to crack the top
5 wettest list. The wettest November on record was back in 2006 when 11.92” of rain was
collected. Still our water year Oct. 1st - Sept. 30th, is off to a good start with a current total of
10.13 inches. The surplus may be smaller than you think at +1.47 inches.
I am eyeing a much colder weather pattern arriving around December 9th, bringing days of snow
Residents of the northwest bracing for possible heavy rain event this evening through Friday night.
A weak atmospheric river will accompany a warm front tonight to bring hours of steady rain, heavy at times into Thursday morning. Widespread rain tonight will drop at least .50” of rain over Portland and Salem with valley amounts possibly nearing an inch. The warmer air will lift snow levels above 8,000’ by morning, meaning all rain at Mt. Hood resorts.
While surface winds will be breezy, south 10-20 mph, wind will generally not be a concern through the forecast period. People living at elevations above 1,500 feet should expect constant southwest winds between 20-30 mph. The warm moist air will bring rising temps overnight into Thursday morning, with much of the Portland area waking up to 55 degrees, rain and ponding of water on area roadways.
A forecast update shows the main fetch of steady, heavy rain will push north of Portland into Washington during the day Thursday, bringing a respite of steady rain. Daytime rain amounts Thursday may average as little as .25 inches. Valley high temps will warm into the low 60s.
Rain picks Thursday overnight into Friday morning in what could be a 2nd period of steady, heavy rain as a cold front drops southward into our region. The front may become nearly stationary during the day Friday with the atmospheric river transporting rain over the frontal boundary, producing valley rain totals well over an inch during the day and possible 1.50 inches. As the front drops through our region Friday night, rain ends for a dry Saturday.
2 heavy rain episodes - one tonight and a 2nd Friday daytime. (possible rain break of sorts Thursday afternoon)
Valley rain total: 2.00 -3.00”
Coast rain total: 2.50-5.00”
Coast Range and Cascades rain total: 6.00” and possibly 10” of total rainfall in some drainage basins.
Smaller rivers (meaning not the Columbia or Willamette) may reach flood stage Friday pm hour into the night. High water spots become possible Thursday morning and again during the day Friday.
Mudslides will be a concern over wildfire burn scars.
A warm front Wednesday evening will lead to steady rainfall overnight, adding up to .50" in Portland and beginning a stretch of mostly steady, heavy at times rainfall through Friday evening. A weak atmospheric river will pump Pacific moisture into a convergence zone along a warm front to stationary boundary Thursday. The moisture flow continues Friday as a cold frontal boundary slowly drops south through our region.
Weather models show more than inch of valley rain Thursday and possibly an inch of rain Friday, making for 60 totals between 1.50 and 3" of rain over the Portland metro and much of the I-5 corridor from Albany to Longview. The Coast Range and Cascades could see rain totals of 6-12" through the period, while the coast sees 2.50-5.00 inches. High water spots or urban flooding are expected, along with possible river and stream flooding Thursday night into Saturday. Mudslides in burn scar areas are also a concern.
Snow levels will be high at 8,000' and above Thursday and Friday, meaning heavy rain in the mountains. Elevations above 1,500 feet may see a constant southwest wind between 20-30 mph through much of the period.
Dry weather is expected to return Saturday, either morning or afternoon.
This winter's outlook begins with what is fairly rare, a back to back La Nina winter season. Our region is projected to have a moderate La Nina winter, matching last season's Enso cycle. This will become just the 10th back to back La Nina since the cycle was documented starting in 1950.