Portland’s Driest April In 50+ Years

April 28, 2020

11pm Tuesday…

Today was another very nice spring day.  Temperatures rose into the lower 70s west of the Cascades (except along the coastline).  This is what we typically see around Memorial Day, still a month away.

web_ORWA_HIGHS_Today_West

Every day except the first four has been at/above average as well.

Do you realize this is the driest month in Portland since last July?  That’s very dry for April.  It looks like we’ll see less than .20″ rain coming up with a weak system Wednesday evening and early Thursday.  That means we end up with less than 1.00″ for the month.  We haven’t seen that since 1966.

MarkDrySpells April

And what a change from the past few years…I remember the closed sports fields (standing water) in 2017 & 2018.

MarkDrySpells April2

The warm and dry April has taken quite a toll on the mountain snowpack, it’s melting much quicker than what we’d typically see.

Compare the April 1st “snow water equivalent” to the 28th.  Below 50% of average now in parts of southern Oregon and close to that 50% number in central Oregon.  These numbers will continue to drop the next 10 days since we see more warm weather next week

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What’s ahead?  I see more of the same…drier and warmer than normal the next 7-10 days.  But that DOESN’T mean totally dry weather.

A strong upper-level ridge across the western USA is keeping weather systems very weak as they move by the Pacific Northwest.  This is tomorrow.

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That ridge weakens quite a bit and a cool airmass attempts to move inland this weekend…this is Sunday.  Notice below normal heights across the entire northeastern Pacific, but it’s not directly over us.  Showery, but not crazy wet or cold.

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But by the middle of next week the warm upper-level ridging returns, this time perhaps directly overhead

ecm_wed_6th

These maps are all from the European model ensembles, but other models are similar.  This COULD lead to our first 80 degree weather next week.  For sure we see another spell of mainly dry weather after this upcoming weekend.  This is 24 hour rainfall for each of the GFS ensemble members (one horizontal line per member) centered over the northern Willamette Valley.  You see the weekend showers, then very few members are forecasting significant rain next week.  Many are totally dry.

gfs-ensemble-all-KMMV-indiv_qpf_24-8075200

So, it’s been a nice spring but we could sure use a major week-long soaking sometime in May!  For now I don’t see any sign of that happening.

Chief Meteorologist Mark Nelsen