Rainy & Windy Sunday Night Ahead

April 15, 2018

9:00pm Sunday

Surprise…it’s still raining!  What a gloomy April Sunday don’t you think?  We’ve picked up about a third of an inch of rain here in Portland, but more than 1/2″ fell once again in Salem.  Yesterday over 2″ fell in parts of western Washington.  Yes, April has been much wetter than average.  We’re halfway through the month; check out those monthly totals so far!

That Portland total is the 4th wettest first half of April on record.  We’ve seen rain on 12 of 15 days this month:

But the weather pattern will become far more “reasonable” this week.  By that I mean we’ll be drying out quite a bit…after Tuesday.

Tonight we have a deepening surface low pressure center traveling straight north through NW Oregon and a 2nd low moving north through Eastern Washington and northern Idaho.  Here’s the 8pm position of the low:

By 2am note the lowering pressures over Washington, both western and eastern sides of the state.  Quite a southerly gradient through the Willamette Valley!

Then by 8am the weaker low has been absorbed by the 989mb center in southern British Columbia.   This is a windy pattern for the Pacific Northwest so you can expect a windy day Monday after tonight’s gusty wind.

We’ve already seen gusts in the 30-40 mph range in parts of the Willamette Valley and south metro this past hour.  I see a 35 mph gust suddenly just arrived at I-205/Division ODOT sensor and a 39 mph gust at Aurora.  We have 12-18 hours of wet & windy weather on tap.

Here’s the good news!  In the past 3 days models seem to be keying in on a change…actually 2 changes for the next 10+ days:

  1. The upper-level troughs moving along the westerly flow appear to get weaker/milder and don’t dig as far south
  2. Upper-level heights rise as the weakening spring jet stream pushes farther north more often.

The result is a significantly drier and somewhat warmer weather pattern.  It appears we’re going from mid-March cold troughs to more of a May-type pattern.  Take a look at the ECMWF ensemble precipitation forecast:

You can see almost all ensemble members are dry from Wednesday through early next week, minus the shower chance Saturday morning as a trough passes by to the north.  This is the driest chart we’ve seen in many weeks, maybe since early February.  Notice temperatures rise quite a bit too, this is from the 18z GFS:

To wrap it up…AFTER Tuesday I see a much milder/nice mid-spring weather pattern ahead.  Not totally dry, but our gardens/lawns/fields will get a chance to dry out.

Chief Meteorologist Mark Nelsen