Stable & Dry Summer Weather Pattern Arrives Early

10pm Tuesday

Today was about as “average” as it gets for a late June day.  We hit our typical high of 76 with afternoon sunshine following the morning cloud cover.  And of course it was dry as well.  Here in Portland we haven’t seen measurable rain in 11 days:

Mark Dry Spells Summer Recent

Remember that 2012 dry spell?  It didn’t start until early September!  That was a strange early fall dry period.

We have turned dry because those showery spring upper-level lows have weakened and are staying well to the north.   So basically weather maps and models look just like July/August right now and we have entered the warmest/driest time of the year in the Pacific Northwest.  It’s time to hit the rivers, mountain lakes, Gorge, Coast, hiking, camping, bicycling and anything else you wait all fall/winter/spring for. We’ll get just enough onshore flow over the next week to keep hot weather away, but we WILL see a thinner marine layer the next few days.  That means slightly warmer temperatures.

Then a few weak disturbances slide by later this weekend and the first half of next week; that will increase the onshore flow = increasing morning clouds & cooler temps.

Take a look at the Global Ensemble Forecast System (GEFS) temperature anomaly (departure from normal) over the next 16 days.  The general trend is clear…warming the next few days, a downturn but only to around or slightly below average around the 3rd/4th.  Then warming again after the 4th.  A very stable pattern with mainly above average temps.


A different way to look at it; the ECMWF ensemble chart showing maximum temperature from its 51 different members


You see quite a few members showing this Friday as the warmest day (the 30th) and then warming again around the 5th/6th.  This shows good agreement among two different models.

As for rain…it looks very dry.  Sure, we can always sneak in some sprinkles or marine air drizzle, but that’s about it.  The GEFS says little or no rain the next 16 days.  Each horizontal line below is one of the 21 ensemble members.


So enjoy the weather…you’ve waited MANY months for these few guaranteed warm and dry weeks of the year.

By the way, on a side note, today is “melt-out” day at the Mt. Hood SNOTEL Test Site.  This evening the snowpack is just about all gone at that 5,400′ elevation.  The last week it has been melting very quickly.  3 days ago there was 10″ of water content in the snowpack, this evening it will be down to just under 2″ by midnight.  That’s the threshold I use for this graph showing the melt-out date for the past 36 years:


Until the last 3 years the average date hadn’t changed much, but the very early melt-out the past two years (late May and early June) mean the trend is EARLIER for snowmelt AT THIS ELEVATION on the mountain.  We’re only talking a few days, but something to keep an eye on in coming years.  With a warming climate one would assume the date will gradually creep earlier and earlier.  We’ll see.

Chief Meteorologist Mark Nelsen

5 Responses to Stable & Dry Summer Weather Pattern Arrives Early

  1. Jesse-SW Portland Suburbs says:

    This is the copy of a comment made by “wx_statman” on the Weather Forums, in regards to Mark’s comments about the record heat in Astoria on Saturday. Some interesting stuff here. It would be good to see you address the data “scrubbing” issue at some point in a blog post. Mark! I don’t know if you are aware of it.

    Looks like Mark Nelsen is going with the newly scrubbed numbers for Astoria (I don’t know whether he realizes it or not). The record books at Astoria and numerous other stations have been destroyed by the QC’ing process that NCEI implemented last year to U.S. weather data. NCEI is the official repository for U.S. weather data, and places like the NCDC, WRCC, Threadex and the Utah Climate Center draw from NCEI’s database of daily observations for official U.S. weather stations. As far as I know, in an effort to scrub erroneous readings, NCEI simply applied blanket statistical correlation formulas to the weather data. This process knocked out many of the “outliers” which in fact represented legitimate extreme events.

    For AST, the all-time record high of 100 on 7/11/1961 was scrubbed from the record books along with many other extreme maximum readings from the past (96 on 8/9/1981, 95 on 8/13/2002, 93 on 5/16/2008, 93 on 6/8/1955, etc).

    So this has led Mark Nelsen to say:

    The 93 at Astoria was the 4th warmest temperature on record out there. The all-time high at Astoria Airport is 98, set just last August. The 1st, 2nd, & 4th highest temperatures ever observed at AST have been set in the past 15 years. I think a coastal heat wave blog post is in order at some point…”Is Heat Becoming A More Regular Visitor to the Oregon Coast?”

    As it turns out, nothing in that paragraph is accurate. It’s really unfortunate.

  2. Roland Derksen says:

    I remember summer 2012, but I also recall a much earlier summer(1986) where I counted 54 days in a row without measurable precipitation. The intresting thing about both those
    summers were that they began quite wet and cloudy, then turned much better later.

  3. Lee Wilson says:

    Well, maybe we can put another dent in our PUD Bill 🙂

    Now the reason why the meter the usage reads like this is because we are on a budget pay system.

    Each “-” we get is equal to an amount we saved in Killow Wat Hours.

    During the hot spell we were able use a generator and our Solar combined to stave off the high cost of running 2 air-conditioning units.

    How ever we can also mass in one room and run a single Air-conditioning unit run the fridge and all our electronics .

    I use the weather to plan what we will use.

    If what you are saying is true , then Mark, were looking at virtually free power …

    Take care my friends..

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