IbrChris

Well hello there...

00z ECMWF really showed little change from the last two runs until the transition phase. Two days in the mid 20s at PDX with perhaps four days with highs 32 or below. Two nights near 15. Pretty amazing for Feb. For Seattle the coldest high shown is 29 and low of 17.

Strong possibility of highs 20-25 on the coldest day next week @ PDX with sub-freezing highs for up to 4 days (3 seems more likely). This is gonna be pretty phenomenal in historical terms even before the snow flies.

-EPO ridge returns...CFSv2 has been showing it for the past 30 days of runs. If it's broad and lower amplitude, east gets cold. If it's more amplified, west/central US is the focal point. I wouldn't write off winter for anywhere in the lower 48 yet, besides perhaps southern California.

Last three runs of the ECMWF have shown highs in the upper 20s at PDX. Granted those runs have averaged about 2-3c colder than the GFS at 850 mb. A couple days with highs in the 20s would not surprise me at PDX, with a bit lower odds at Seattle.

Ya, 20/20 hindsight. We have a historic arctic blast on the way across the PNW.

Word on the street is 12z ECMWF Op is ridiculously cold. -16c at coldest point at hour 144 (run is currently processing).

CFSv2 runs averaged over the last 30 days (120 runs) seem to be set on keeping the anomalous ridging near the Aleutians through March, perhaps into April. In talking with several met friends of mine including a met at NWS' Portland office it appears this persistent of a ridge in the North Pacific during winter is unprecedented, at least in the 1948-present reanalysis period.

I don't have to spend time here, I forecast for a living. Won't bother me any.

My educated opinion is that we will see a week or so of general -5 to -7F surface temp anomalies over the PNW, along with weak systems in NW flow. This should be a good pattern for modest snowpack gains in the Cascades with snow levels dipping down to 2,000' or so. I see nothing to indicate a snow threat in the lowlands at this point with 850 mb temps on both the GFS and ECMWF ensembles not dropping below -4 or -5c through the next two weeks. The ECMWF Weeklies show a slightly better looking pattern during week 3 assuming the block near 160 W undergoes a pulse of amplification, that could bring in a bit colder air if it occurs.

My guess would be up to a week of general -5 to -7F sfc temp anomalies across the PNW corresponding to a 2000-3000' snow level with weak systems in NW flow. In other words highs generally 40-45. Neither the Euro or GFS ensemble mean are indicative of 850 mb temps below -4 or -5c.

ECMWF Ensemble 11-15 day composite 500 mb anomalies suggest a brief backdoor intrusion of cold into the interior west, however the mean trough over the east tends to make me think it will be quite transitory unless a decent block materializes near 160 W. As is the arctic air should translate east quickly and be mainly a Rockies eastward event.

CFS has trended further NW with the Feb cold anomalies...at the surface. It keeps a suppressed ridge over the interior west and the mean 500 mb trough oriented roughly SW-NE across western Canada and off the W coast. This sol of course brings the precip back to the west coast (including Cali) strongly, with 5+" monthly precip anomalies across SW OR/NW CA. I consider the CFS less trustworthy than the ECMWF Weekly product, CFS puts too much weight on the 11-15 day solutions offered by the GFS+ensembles when forecasting the month in advance, a pretty fatal flaw IMO. This results in intense flip-flopping in the lead-up to the month. I saw 180 degree swings in the thinking of the CFS from runs within about a week of each other back in Nov (for Dec 2013). Weeklies have much better run-to-run continuity and have verified better in the week 2+ timeframe than CFS.

Oregon at the moment. I agree, the eastern troughing has been the persistent theme since about mid December and I am also skeptical that the SE ridge develops, although the ridge shifting back to ~160 W should help focus the cold a bit further W, assuming it occurs. The ridge as shown would need to amplify more to drive the cold down west of the Rockies, as it stands here this would mainly support cold from the divide to about MN/Dakotas with more ephemeral effects further E. The highly anomalous NE Pac/AK blocks have largely controlled the position of the mean trough downstream. Take away the block and you'd see a lot more zonal flow across the lower 48 and a much milder pattern in general. This becomes more obvious when you look at the entire NH longwave pattern, NE Pac ridge is the initial perturbation, then downstream you have longwaves of generally decreasing amplitude until and unless there is a new feature that serves to perturb the 500 mb pattern (usually some sort of high-latitude block). Stronger waves crest and beat down the NE Pac ridge which then rebounds in their wake, often a bit further W than previously. Around New Years a strong trough developed over the Bering Sea/Alaska in response to ridging popping over Siberia. That Bering trough then translated east and was absorbed into the PV over Hudson Bay, lobes of which have been far enough S to deliver arctic air into the OH valley and SE US as well as the more usual locations. Yes I realize we don't live at 500 mb.

Weeklies are looking good toward early-mid February. Potential for cross-polar flow toward mid Feb. I like that SE ridge, although the Euro Weeklies have tried to elongate the Azores-Bermuda ridge into the SE US on several occasions when it hasn't panned out. Last gasp of winter 2013-14...if this fails to materialize I think we can stick a fork in it as far as lowland snow/cold. March could still deliver a borderline weak event but not the kind that sticks around for a few days and closes schools etc.