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 00Z Thu

Satellite imagery and terminal observations as of late Tuesday morning depicts widespread smoke across northwest Oregon and southwest Washington as easterly push wildfire smoke into the area from central/eastern Oregon. Latest PIREPs and METARs suggest that the top of this smoke layer is generally around 5 kft, with smoke also mixing down to the surface. Given that offshore winds will continue into Wednesday and keep smoke in the area, FU and HZ has been included in the TAFs throughout the forecast period. Still expecting predominately VFR conditions, but smoke will likely reduce visibility to 3-5 SM for most Willamette Valley terminals. 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. While winds remain predominately easterly through the Columbia River Gorge and Cascades, expect winds out of the north/northeast for the majority of terminals for the rest of the afternoon with gusts up to 25 kt along the coast and up to 20 kt across the Willamette Valley. Winds ease overnight.

KPDX AND APPROACHES...VFR conditions through the TAF period with smoke reducing VIS to 5-6 SM at times, mainly the latter. North to northwesterly winds around 5-10 kt this afternoon and weakening under 5 kt tonight. -10

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

FIRE WEATHER...Today through Thursday

Easterly flow continues through the Columbia River Gorge and along the Cascade crest-line down into the foothills today. Gusts around 15-30 mph have been observed, strongest in the wind-prone locations through the Columbia River Gorge (Three Corner Rock). Relative humidity values have also fallen to around 19-28%. These winds will continue through the afternoon, along with the degraded relative humidity values, leading to critical fire weather conditions capable of rapid fire spread. Conditions then remain dry and breezy in the western Gorge as easterly winds continue tonight into at least Wednesday morning, though peak gusts expected to decrease a bit. A Red Flag Warning remains in effect for the western Gorge, fire weather zone 636, from 11 AM PDT today through 8 PM PDT Wednesday.

Through this same time period the rest of the Cascades will have relatively weaker easterly winds with gusts generally in the 15-25 mph range, strongest through early Wednesday. One exception would be on exposed ridgetops and west- east oriented valleys where slightly higher wind gusts are likely. Nevertheless, elevated fire weather concerns will exist in these areas, as well as in the Portland metro and Willamette Valley where NNE to NE winds are expected to gust up to approximately 15-20 mph into this evening. Fire weather concerns decrease on Thursday albeit with one potential exception. Thursday is when we transition to onshore flow, which will bring breezy westerly winds in the central Gorge and Hood River area. Given conditions will still be dry, elevated fire to near critical weather concerns remain in place. -99/23/03

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.