Thursday, July 30, 2015

West Coast Heat Wave Threatens All-Time Records; Northeast Hot, But Not Historic

Chris Dolce
Published: July 30,2015



 
Summer heat is gripping opposite sides of the country into this weekend, including parts of the West and the Northeast.
The heat will help clinch one of the hottest Julys on record for some Northwest cities, and a few locations may challenge their all-time or monthly record highs on Friday. It's also helped set a record for the most 90-degree days in a year in Seattle and has given Portland its hottest temperatures since 2009.
The Northeast heat will not be as extreme, but it will stick around into next week for some cities.
Let's break down the forecast details on this summery weather pattern for both regions.

Northwest: Clinching a Record Hot July?


Current Northwest Temperatures

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A strong ridge of high pressure is building over the Northwest as the jet stream bulges northward to the Canadian border. This is allowing temperatures 5 to 20 degrees above average to take hold across parts of northern California, Oregon and Washington into the weekend, while also spreading to portions of Idaho and Montana.
(MORE: Strange July Weather Pattern Brings Snow, Tornadoes)
It's a fitting end to what will be one of the hottest Julys on record in parts of the Northwest. Seattle, Washington, and Eugene, Oregon, were both seeing their hottest July on record as of July 27, according to data from the Southeast Regional Climate Center. For Seattle, July 2015 could beat out August 1967 for the hottest month on record if the final average temperature for July exceeds 71.1 degrees.
July was the second warmest on record through July 27 in Portland, Oregon, and Yakima, Washington.
High temperatures at or above 100 degrees are forecast for the Portland, Oregon, area into Friday, with middle to upper 90s expected this weekend. Portland hit 103 degrees on Thursday, which is the hottest temperature there since July 29, 2009. Even hotter temperatures are expected for the rest of the Willamette River Valley of western Oregon, which is under an excessive heat warning issued by the National Weather Service.
Highs in Eugene and Salem, Oregon, are expected to be in the middle 100s on Friday. Eugene has a decent chance of tying its July record high of 106 degrees set July 28, 2009. Salem and Eugene both set daily record highs on Thursday by topping out at 105 degrees and 104 degrees, respectively.
In Corvallis, Oregon, Thursday's high of 108 degrees unofficially tied the all-time record high set Aug. 10, 1981, according to Chris Burt of wunderground.com. The reason this is unofficial is because weather records for Corvallis - which date back to 1889 - are from Corvallis State University, while Thursday's 108 degree reading was about five miles south at the airport.
Farther south, Friday's high in Roseburg, Oregon, could challenge the all-time record high of 109 degrees set July 20, 1946. Roseburg was one degree short of this record on Thursday when it topped out at 108 degrees. Records in Roseburg date back to 1931.
Seattle will likely see highs near 90 degrees through Saturday. The Emerald City saw its tenth 90-degree day of 2015 on Thursday, which is a new record for the most 90-degree days in a calendar year. The old record was nine days set in 1958. Seattle averages just two days with 90-degree heat annually. A heat advisory has been issued by the National Weather Service for the Pudget Sound area through Saturday.

Forecast Highs

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The hot, dry conditions are also increasing the wildfire danger across the Pacific Northwest. The National Weather Service has issued red flag warnings for this fire danger in western parts of Oregon and Washington through Friday.
For parts of central and eastern Washington, this round of hot temperatures probably won't be quite as intense as the late-June record-breaking heat wave. Yakima peaked at 108 degrees in that heat wave, setting a June record. This time around highs are forecast to be 100 to 107 degrees into early next week. Spokane hit 105 degrees in late-June, but should hold in the upper 90s to near 100 degrees through the weekend.
Farther south, Medford, Oregon, could approach 110 degrees on Friday. The high temperature has only reached 110 degrees there on nine days since 1911 – on average, one day per decade.
On the other hand, Boise, Idaho, will just squeak past 100 degrees for the next few days. Idaho's capital should fall well short of its June 28 high of 110 degrees, which set an all-time record for June.
In Northern California, Redding topped out at 114 degrees on Thursday. Sacramento (downtown) set a daily record high of 107 degrees on Wednesday. Temperatures will trend downward in both of those cities by this weekend, but it will remain hot.
For parts of Montana, this is quite a change from the way the week started.  For example, Missoula, Montana, saw rain with temperatures in the upper 40s and 50s on Monday afternoon. The high was 90 degrees there on Thursday and middle to upper 90s are possible this weekend.
High elevation areas that saw snow on Monday in the northern Rockies will also see significant temperature rises. Big Sky, Montana, could be near 80 degrees this weekend.

Northeast: Heat Wave Possible in Some Cities


Forecast Highs














Wednesday was the hottest day so far in 2015 in New York City (96 degrees) and Albany, New York (95 degrees). Concord, New Hampshire, set a daily record high of 96 degrees, beating the old record for July 29 of 95 degrees set in 1949.
Highs will stay a handful of degrees above average for mainly eastern sections of the region into early next week.
For the most part, this heat in the Northeast will not be record breaking. However, the longevity of it will likely be greater than we've seen so far this summer in some cities. By early next week, some locations could meet the definition for a heat wave in the Northeast, which is generally defined in that region as three or more days in a row with temperatures at or above 90 degrees.
(MORE: Daily Forecast Maps)
That said, there will be a big difference between the way it felt Thursday and the way it will feel Friday into the weekend across the Northeast. This is because much drier air will filter in behind a cold front that brought strong thunderstorms to the region on Thursday.
As a result, the humidity that has added to the discomfort will drop significantly, making the heat more bearable. For example, Washington, D.C. had an actual high of 92 degrees with a peak heat index of 103 degrees on Thursday. Friday's high will be just as warm, but with lower humidity the heat index should be in the low to middle 90s.
New York City is likely to see highs mainly in the low 90s into early next week. So far this year, the Big Apple has experienced six days with 90-degree heat. Highs in the 90s were recorded on back-to-back days for just the second time this year on Tuesday and Wednesday.
Highs in Hartford, Connecticut, and Providence, Rhode Island, will likely be in the low 90s or upper 80s into next week.
Farther south, the Mid-Atlantic will sizzle through highs in the low to middle 90s into next week, including Washington, D.C.Baltimore and Philadelphia.
Washington, D.C. has already seen its fair share of 90s in 2015, with 32 days total through Thursday. They will likely meet or exceed their annual average number of 90-degree days in the next few days which is 36.

MORE: Northern Rockies See July Snow

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