AgWeatherNet Weekly Weather Outlook for July 24 to July 30, 2020

Another short-lived heat wave early next week and an increasing threat of wildfires

Mark Ingalls, AgWeatherNet Intern
Michelle Daughtrey, AgWeatherNet Intern
Joe Zagrodnik, AgWeatherNet Postdoctoral Research Associate

Discussion:

The big story for the next week is a significant but short-lived heat wave during the first half of the week. The ridge of high pressure responsible for the heat wave will gradually build over the weekend and reach its apex on Monday and Tuesday, which will be the hottest days across the state. Currently (Friday), temperatures remain relatively cool and breezy, as strong flow from the west is keeping many west of the mountains under a marine influence. Temperatures will begin climbing Saturday and Sunday. East of the Cascades, they are expected to reach about as high as the first heat wave that occurred over the past week, peaking on Tuesday. It looks as though western locations will be somewhat warmer in this event. The high pressure that will cause this event is expected to shift eastward Wednesday, bringing a return to cooler, onshore flow by Thursday at the latest.

Winds are currently picking up in Eastern Washington as a weak shortwave trough moves through the region. As usual, the breeze will be most pronounced in leeward valleys like Kittitas Valley and the east end of the Columbia Gorge, but this breeze should be felt throughout most eastern lowland locations. That trough is out of the area by Saturday, when an upper level ridge is expected to begin building across the Pacific Northwest. Temperatures will warm, peaking on Monday in Western Washington and Tuesday in Eastern Washington. For the west side, temperatures will be a bit warmer than the most recent heat wave. Along I-5, instead of having 90° temperatures be limited to areas south of Portland, they may reach into King County. Heading west from I-5, temperatures will gradually cool to the low-70s on the Pacific Coast. In Eastern Washington, expect temperatures to peak around what was experienced Tuesday (July 21). Expect the mercury to rise to around 105° in the Tri-Cities, 100° in Yakima, and the upper-90s for Spokane.

The high pressure responsible for this heat will push somewhat eastward on Wednesday, but this doesnt mean that warm temperatures will be going away (except on the coast, where highs will cool into the mid-60s). Along I-5, the 80° line is expected to lie between Tacoma and Seattle and the lowest elevations of Eastern Washington should still be near 100°. There is a low chance of afternoon thunderstorms in far Southeastern Washington and the Okanogan on Wednesday. Any storms that do form are expected to bring little-to-no precipitation which runs the risk for dry lightning to start fires.

Models are indicating the presence of an upper level trough on Thursday that could bring some light precipitation to Western Washington and the Cascades. This will be moving northeast into British Columbia limiting impacts in the eastern half of the state, but it will likely tighten surface pressure gradients across the mountain range to generate another round of breezy conditions Thursday. For Friday and next weekend, it looks like our pattern will be dominated by an upper level trough off the coast that should keep the pattern generally dry and warm.

Heat related illnesses are a concern this week as temperatures rise again. Temperatures this week arent expected to break numerous records, but they will still be dangerous to those working outdoors, especially in the Columbia Basin and surrounding valleys. Be sure to drink plenty of water and be aware of the symptoms of heat related illnesses for yourself and others. According to the National Weather Service, heat is the number one weather-related killer in the United States, beating out other extreme events such as floods, hurricanes, and tornadoes.

Climatologically, the Pacific Northwest has reached its driest stretch of the year. On top of this, hot temperatures, low humidity, and intermittently breezy periods will also enhance the need to be fire aware this week. Arid portions of the state are well within their fire season, but the forests of Western Washington are drying out from this springs precipitation. Fuels are becoming more susceptible to burning, with the highest concern being on the east slopes of the Cascades, in Blue Mountains, and the Okanogan. While forest fires can start anywhere this time of year, westerly flow should help to keep humidity values out of abnormally dangerous ranges west of the Cascade Crest this week.


8 to 14 Day Outlook, July 31 to August 6, 2020
  • Above average temperatures and below average rainfall are favored during the 8 to 14 day time frame.

Important Points about Next Week's Weather

South Central Washington
Weekend
  • Wind: Mostly W/NW, a light breeze Friday with gusts to reach 30mph but light to calm Saturday and Sunday. Gusts not to exceed 20 mph.
  • Precipitation: Dry conditions expected throughout the weekend.
  • High Temps: Mid to upper 80s Fri, upper 80s Sat, mid 90s Sun.
  • Low Temps: Low 50s Fri night, low 50s Sat night, upper 50s Sun night.
  • Sky Cover: Partly cloudy Fri and Fri night, clear Sat and Sat night, partly sunny Sun.
Next Week
  • Wind: S/SW lightly breeze Monday, switching back to W/NW Tuesday and continue to be generally calm. Gusts reaching up to 40 mph Wednesday Returning to calm conditions Friday.
  • Precipitation: Dry conditions maintain in the region until Wednesday night, with a chance for a light shower moving in from the West.
  • High Temps: Upper 90s Mon, 100 Tue, low 100s Wed, upper 90s Thu.
  • Low Temps: Low 60s Mon night, low 60s Tue night, low 60s Wed night, upper 50s Thu night.
  • Sky Cover: Clear Monday, partly cloudy Tues and Wed, mostly clear Thurs.

North Central Washington
Weekend
  • Wind: Light W/NW but variable expected throughout the weekend. Gusting to reach 40 mph Friday night but remain calm Saturday and Sunday.
  • Precipitation: Dry conditions expected throughout the weekend.
  • High Temps: Mid 80s Fri, upper 80s Sat, low 90s Sun. Much cooler through the Cascades and Olympics.
  • Low Temps: Mid 50s Fri night, low 60s Sat night, mid 60s Sun night. Much cooler through the Cascades and Olympics.
  • Sky Cover: Partly cloudy Fri. Mostly clear Sat and Sun.
Next Week
  • Wind: Light S flow Monday, transitioning to W/NW Monday night and returning to light S/SW Tuesday throughout the rest of the week. Gusts to reach 30 mph Tuesday through Thursday evening.
  • Precipitation: Dry conditions expected to continue throughout the week.
  • High Temps: Upper 90s Mon, upper 90s Tue, low 90s Wed, upper 80s Thu. Much cooler through the Cascades and Olympics. Cooler near the coast.
  • Low Temps: Low 60s Mon night, low 50s Tue night, low 60s Wed night, upper 40s Thu night. Much cooler through the Cascades and Olympics.
  • Sky Cover: Mostly clear Mon, partly cloudy rest of week.

Eastern Washington
Weekend
  • Wind: Light and generally W/SW Friday. Saturday transitions to light N/NW but variable. Light and S/SE Sunday morning but changes to N/NE Sunday Evening. Gusts Friday reaching 25-30 mph.
  • Precipitation: Dry conditions expected throughout the weekend.
  • High Temps: Upper 70s Fri, upper 70s Sat, upper 80s Sun.
  • Low Temps: Low 50s Fri night, mid 50s Sat night, low 60s Sun night.
  • Sky Cover: Partly cloudy Fri, mostly clear Sat and Sun.
Next Week
  • Wind: Light S/SE but variable flow throughout the week with gusts Thursday reaching 40 mph.
  • Precipitation: Chance of scattered showers Wednesday evening in the Western part of the region along the Columbia River.
  • High Temps: Low 90s Mon, mid 90s Tue, mid 90s Wed, near 90 Thu.
  • Low Temps: Low 60s Mon night, low 60s Tue night, low 60s Wed night, mid 50s Thu night.
  • Sky Cover: Clear Mon, partly cloudy Tues and Wed, mostly clear Thurs.

Western Washington
Weekend
  • Wind: Light and generally S/SW yet variable Friday. Becoming calmer Saturday with winds shifting N/NW. Winds remain light Sunday but shift to N/NE offshore flow.
  • Precipitation: Light scattered showers Friday morning into the afternoon. Saturday and Sunday expected to trend toward dry conditions.
  • High Temps: Low 70s Fri, upper 70s Sat, mid 80s Sun. Much cooler through the Cascades and Olympics.
  • Low Temps: Upper 40s Fri night, low 50s Sat night, mid 50s Sun night. Much cooler through the Cascades and Olympics.
  • Sky Cover: Partly to mostly cloudy Fri, becoming partly sunny Sat. Mostly clear through Sunday night.
Next Week
  • Wind: Offshore S/SE pattern continues into Monday, while calm to lightly breezy conditions continue. Winds shift Tuesday to W/SW and remain light but variable throughout the week.
  • Mostly light and W yet variable. Winds shifting mostly NW Wednesday night and becoming breezier. Winds expected to remain breezy through the end of the week.
  • Precipitation: Dry conditions persist through Wednesday. A system will move across the region Thursday afternoon bringing showers across the region. Friday returns to dry conditions.
  • High Temps: Mid 80s to low 90s Mon, low 80s Tue, upper 70s Wed, upper 70s Thu. Much cooler through the Cascades and Olympics. Cooler near the coast.
  • Low Temps: Mid 50s Mon night, low 50s Tue night, upper 40s Wed night, low 50s Thu night. Much cooler through the Cascades and Olympics.
  • Sky Cover: Clear Mon, partly cloudy remainder of the week.

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