textproduct: Portland

SYNOPSIS

Hot, dry, and smoky conditions are on tap for southwestern Washington and northwest Oregon through midweek. High temperatures for most inland valley locations peak in the low to upper 90s through Thursday, though wildfire smoke may dampen temperatures from rising by a few degrees. However, temperatures will still be warm enough for widespread Moderate to locally Major HeatRisk impacts. Temperatures begin to trend touch cooler Friday into the weekend with the return of onshore flow with winds from the west, which will also push any lingering wildfire smoke and haze back east of the Cascade crests. Fire weather concerns remain in the forecast through Wednesday primarily focused in the Columbia River Gorge and Cascades.

DISCUSSION...Tuesday afternoon through Monday

Temperature observations at 3 PM PDT indicate temperatures are around 6 to 10 degrees warmer than 24 hours prior, reporting in the mid 80s to low 90s for any inland areas. Downsloping easterly winds off of the Coast Range have warmed some coastal locations such as Astoria, Tillamook, and Pacific City to the upper 70s to 80 degrees. This warming trend is due to an amplifying upper level ridge of high pressure moving from the eastern Pacific over the West Coast. However, temperatures have not warmed quite as much today as previously forecast for most inland locations due to the influx of wildfire smoke into NW OR and SW WA from wildfires east of the Cascades under generally easterly wind flow.

The high pressure peaks over the region Wednesday and Thursday, which will allow temperatures to warm even more. Current forecast indicates high temperatures could rise into the mid to upper 90s each day for the interior lowlands. However, smoke is expected to continue impacting the area through at least Wednesday as the offshore flow with winds from the east continues. This means high temperatures could once again be impacted by the smoke and might not peak quite as high as forecast. Additionally, as the upper level ridge slowly moves into eastern OR/WA late Wednesday into Thursday, the flow will begin shifting onshore or from the west. There is some uncertainty on exactly when this shift will happen, but it will begin pushing smoke back east of the Cascades. If smoke clears out earlier on Thursday, then temperatures could peak at the forecasted warmer temperatures. If it doesn't clear out until later Thursday, smoke could continue impacting temperatures.

Regardless of the exact outcome of the temperatures, conditions will be warm enough to bring an increased risk of heat-related illnesses. As such, various Heat Advisories remain in effect for most inland valleys through Wednesday. In areas with Air Quality Advisories in effect, it is recommended to keep windows and door shut to prevent smoke from going indoors. However, those without air conditioning who are counting on opening their windows at night to help cool down will have less options. In this scenario, something as simple as a large box fan with a damp towel draped over the front of it can be surprisingly effective given the dry airmass in place. This could also cause an impact even with slightly lower daytime temperatures as houses may retain more heat if windows can't be opened to adequately cool off.

Heading into Friday the axis of the broad upper-level ridge feature moves east of OR/WA, helping to increase onshore flow. That said, there will likely be enough influence from the high pressure ridge aloft to keep high temperatures in the low 90s across the inland valleys into Saturday. At least at this point any lingering wildfire smoke should be flushed from west of the Cascade crests. Onshore flow is expected to strengthen further over the weekend into early next week, allowing temperatures to cool back to near normal with moderate to high confidence for maximum temperatures returning to the low to mid 80s by Sunday/Monday. -03

AVIATION...Through 06Z Thu

Smoky skies continues to be the main concern across the area tonight through Wednesday. An upper level ridge of high pressure will continue to build over the region maintaining westerly flow aloft. Meanwhile, east to northeasterly flow in the lower levels will continue to draw wildfire smoke west of the Cascades through at least Wednesday morning. As of 04z Wed, surface observations continue to show reduced VIS to 4-6SM due to the smoke and haze across much of the Willamette Valley. Improvement to VFR conditions is expected as the surface inversion develops and smoke remains more aloft overnight after 06z. By late Wed morning into the afternoon, temperatures are again expected to warm into the upper 80s to lower 90s, allowing for more mixing of the atmosphere which would likely increase smoke toward the surface, reducing VIS again to around 5SM. The nearest major wildfire is the Grasshopper Fire east of Mt. Hood, and areas in the vicinity and to the west of this fire will experience the densest smoke with the greatest VIS impacts. Winds are expected to become more westerly in the lower levels later Wed afternoon and evening, which could help conditions improve slightly after 00z Thu.

KPDX AND APPROACHES...Predominately VFR conditions are expected except for periods of reduced VIS to 5-6SM due to wildfire smoke in the area. Northwest winds around 3-7 kt expected, strongest in the afternoon and evening. /DH

MARINE

High pressure over the waters will maintain northerly winds through the weekend. Small Craft Advisories remain in effect through 5 AM Wednesday for the Columbia River Bar and inner waters up to 10 NM offshore, and through 5 PM Wednesday for the outer waters between 10-60 NM offshore. Expect northerly winds with gusts up to 25 kt across the waters through late tonight, and weakening below 20 kt by late Wednesday morning. Seas remain mostly wind-driven and around 7-9 ft through tonight, with the steepest seas south of Cape Foulweather. Tomorrow, seas in the outer waters remain steep and choppy around 6-7 ft at 7-8 seconds, which is why the Small Craft Advisory extends into Wednesday afternoon for these areas. Winds and seas subside after tomorrow, with the typical summertime pattern continuing into next week. -10

PQR WATCHES/WARNINGS/ADVISORIES

OR...Heat Advisory until 11 PM PDT Wednesday for ORZ104-105-108>118.

WA...Heat Advisory until 11 PM PDT Wednesday for WAZ204>208.

Red Flag Warning until 8 PM PDT Wednesday for WAZ636.

PZ...Small Craft Advisory until 5 AM PDT Wednesday for PZZ210-251>253.

Small Craft Advisory until 5 PM PDT Wednesday for PZZ271>273.