A Spectacular Period of October Sunshine

October 17, 2018

8pm Wednesday…

It’s been just about perfect once again today; a cool start then a warm afternoon for most of us.  There was just enough offshore flow today to keep the coastline up in the 70s.  Tillamook even hit 80 once again

Todays Observed Highs OrWa 2017

The weather might seem extra nice because temperatures have done the REVERSE of what we typically see in October.  We started out cool and then warmed up mid-month.  In a typical year temps bump up and down through the month but we head downhill in general.

High Temp Last 13 Days

We were just 4 degrees from a record high today and just 3 degrees away from one yesterday.  Today is also our 9th consecutive dry day; quite unusual in October.  But it has happened in the past!  In October 1987 no rain fell until Halloween.  And way back in 1895 (downtown Portland records) no measurable rain fell all month!

Dry Spells October

Easterly wind has been blowing since Sunday in the Gorge, and has been pretty strong for October the past 3 days.  But the pressure gradient across the Cascades is dying down this evening and it’ll just be a “whisper” of east wind tomorrow and Friday.  At least it’s still a “warm” wind.  I’m quite confident that next time it appears it’ll be cooler.  In fact east wind is always cool/cold from Halloween to early March.

Models have been doing a very good job with the big picture and nothing has really changed in the long-range forecast since my last post Sunday evening.  Strong upper-level high pressure is over the West Coast; it flattens a bit tomorrow, then pops back up over the Intermountain region Saturday through Monday.    This means we still have 5 more days of warm and (mainly) sunny skies.  A weak push of marine air could give us areas of fog or low clouds Friday and/or Saturday morning.  Same thing is possible Monday morning.

Rain is on the way for Tuesday.  Check out the ECMWF ensemble prediction system 24-hr precipitation

KPDX_2018101712_eps24_precip_360

That’s a pretty clear signal for rain arriving Tuesday isn’t it?  Every single ensemble member says we turn wet, although not excessively so.  The reason?  The upper-level high that’s over us this weekend:

ecm_sat_20th

is replace by a cool trough and a fast westerly jet over the east Pacific.  Here’s next Wednesday.  Quite a bit different isn’t it?

ecm_wed_24th

That said, this may not be the big start to the rainy season.  I see all three main model ensembles point to renewed ridging (of some sort) about a week later, on November the 1st.

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So get all your dry-weather activities finished up by Monday afternoon/evening, and enjoy the sunshine this weekend.

Chief Meteorologist Mark Nelsen