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Summer forecast backs off the heat a bit for July

Photo: Jennifer Wilsey Landahl

Happy "Third Thursday of the month then the new seasonal forecast maps come out" day! And June's edition has a bit of good news for those who haven't particularly been fond of our last four hotter-than-normal summers: The chances of a hot July have diminished.

The new maps issued Thursday now have the Pacific Northwest painted blank, which is seasonal-map-speak for "equal chances" of July being hotter than normal, cooler than normal, or ending up right around normal. In other words, the forecast models aren't picking up any signal that would weigh the overall month's forecast in any particular direction.

That's a bit of a change as previous forecasts from the winter and spring had been giving the Northwest slightly better odds of a warmer July and summer. Then again, they said the same thing about June -- technically they're still correct so far as Seattle was running about a degree above normal through Wednesday, but aren't factoring in the cool stretch we're in the end of this week, so I suspect June will come in right around normal. All in all, June has gone pretty much by the script -- some sunny and warm days mixed in with marine layer days and a few rainy days.

A "normal" July would be quite pleasant around here -- average highs run in the mid-upper 70s around Seattle. That doesn't mean we still wouldn't have an occasionally hot day, just they'd be better balanced by occasional cool marine flow days. It's those cooler days that have been missing from the past four summers -- we've gone well past our average of 80+, 85+ and 90+ days.

Note that we are still leaning a bit into the higher odds for a warmer than normal period if you add in August and September, but it's not a strong signal. Also note there are no significant trends in precipitation which would tend to lean toward a normal summer's worth of precipitation, which is good and would limit potential for drought.

What's up with El Nino?

It's looking more and more like El Nino will not be a part of the 2017-18 fall and winter -- music to those who like active winter weather with a bountiful snowpack. During the winter, El Nino was the moderately odds-on-favorite to take over this upcoming fall and winter, but then in April, the odds fell to more even-steven.

But now new data and ocean observations suggest the odds of El Nino are falling farther to where neutral conditions are in the 55% likely range and El Nino has dropped to about a 37% chance (with fractional chance returning to La Nina.)

Neutral winters tend to run the gamut -- extended stormy periods; extended quiet periods and really a wide variety. Also most of our greatest storms, be it windstorms, flooding or snowstorms, have historically occurred in neutral years. Neutral winters also tend to have near-normal snowpacks but can vary either way. But for skiers, it's better than El Nino which usually means below normal snowpack.

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