10/23/2014

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Summer's first blast of heat on its way, but it could have been worse

Summer's first blast of heat on its way, but it could have been worse
A sunny day in Seattle on June 28, 2013. (Photo courtesy: Puget Sound Clean Air Agency Visibility Camera)
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SEATTLE -- While much of Eastern Washington is set to bake as if it were in the Desert Southwest, and the Desert Southwest is set to bake as if it were in Death Valley, and Death Valley is set to bake as if it were on the planet Mercury, Western Washington is set to get a little toasty too...

Only we're going to try to mimic Atlanta instead.

The season's first heat wave is on its way, but while several daily, monthly -- and perhaps a few all-time high temperature records are set to be matched or broken across much of the West, Seattle will settle for being mildly hot and moderately humid.

The heat slowly builds this weekend but temperatures will remain manageable, reaching the mid 80s.

It's early next week when we'll likely see our hottest temperatures of the year as the intense desert heat moves north into Eastern Washington and Western Washington will warm by proximity. Lucky for us, the bulk of the heat will remain east of the mountains where highs are expected to climb well into the 100s with Spokane looking at a forecasted high of 102-104, about 105 in Moses Lake, and getting within shouting distance of 110 in the Tri-Cities.

In Western Washington, highs Monday and Tuesday instead will be limited to the upper 80s across much of the area with a few low 90s in the typical hot spots south and east of Seattle -- technically we could call that "record heat" because Monday's record high in Seattle is just 87, but it's low-hanging fruit as most record highs this time of year are in the mid 90s and it's a statistical climate quirk that July 1 has never hit 90.

But with the trade-off in giving up some heat is taking on more humidity. Instead of getting our dry, warming east wind that accompanies our typical heat waves (which had they been here, Seattle would have likely been in the upper 90s this week) we're getting a moist, southerly wind, courtesy of a pesky cut-off low pressure system that's been parked offshore for days. This is the same low that brought us the storms earlier this week and has no signs of moving away.

That low continues to draw some warm, moist air from warmer sections of the Pacific Ocean and push it north into western Oregon and Washington. That's why it's been somewhat muggy this week but will feel even worse once we start increasing the temperatures.

So while official high temperatures will likely be in the 88-91 range, it'll feel a lot warmer with the added humidity -- perhaps a combination of warmth and humidity we haven't seen in quite some time around here.

Models do indicate we'll start to cool down a little Wednesday to the low-mid 80s and perhaps down into the upper 70s/low 80s for Fourth of July Thursday. But the rather high humidity is still going strong.

In fact, the warm, humid air will also bring a threat of thunderstorms next week. Right now, Wednesday has the greatest threat of storms, but possibilities exist for scattered thunderstorms on Tuesday and Fourth of July Thursday as well. They're most likely in the mountains and near the foothills but as we saw earlier this week and last week, some of those storms could drift over into the lowlands. (Eastern Washington also has a moderate risk of thunderstorms mid to late next week as well -- not good with the heat and dry weather and fireworks. Take extreme care out there!)

Long range forecasts finally show relief as we get into Friday and next weekend as we get more of a cooling marine influence. This should bring highs back down into the 70s, and bring down the humidity a bit as well as the flow becomes more westerly.

How hot elsewhere?

While Seattle is essentially dodging a bullet, here are the expected high temperatures across much of the West:

City Friday Saturday Sunday Monday Tuesday
Phoenix, AZ 118 117 115 113 111
Las Vegas, NV 115 117 117 117 114
Laughlin, NV 122 124 124 123 118
Lake Havasu City, AZ 120 123 124 123 116
Kingman, AZ 111 112 112 109 106
Death Valley, CA 126 128 129 129 128
Barstow, CA 114 118 119 117 115
Needles, CA 122 124 125 123 119
St. George, UT 114 115 114 112 111
Yuma, AZ 118 117 114 112 111
Tucson, AZ 112 113 110 107 105
Reno, NV 102 101 104 104 105
Boise, ID 102 101 103 107 107
Ontario, OR 101 100 103 106 106
Tri-Cities, WA 95 94 98 102 107
Walla Walla, WA 94 93 96 102 104
Pendleton, OR 94 93 96 103 104
Salt Lake City, UT 103 104 103 102 100
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