textproduct: Portland

UPDATE

Visible satellite imagery and AQI observations snow smoke is prevalent near the surface across NW OR and SW WA late this morning. 11AM temperature observations indicate that although temperatures are around 6-10 degrees warmer than 24 hours ago, they have not risen quite as much as they should have at this point to reach the original forecast for today, likely due to the impact of wildfire smoke. Additionally, the 13z NBM has brought down the high temperature forecast for today by a few degrees, especially for the interior lowlands which are now forecast to peak in the low to mid 90s instead of mid to upper 90s. As such, have lowered today's temperature forecast to match.

SYNOPSIS

Going through the middle of the week, hot, dry, and smoky conditions are on tap for southwestern Washington and northwest Oregon. High temperatures for most inland valley locations peak in the mid to upper 90s today through Thursday, resulting in a widespread Moderate to locally Major HeatRisk impacts. Temperatures begin to trend touch cooler Friday into the weekend with the return of onshore flow, which will also push any lingering wildfire smoke and haze back east of the Cascade crests. Fire weather concerns remain in the forecast through today Wednesday/Thursday primarily focused in the Columbia River Gorge and Cascades.

DISCUSSION...Now through Monday

A ridge of high pressure continues to amplify just off the coastline over the far eastern Pacific helping to drive our hot, dry, and rather smoky conditions today. Deterministic and ensemble models are in good agreement showing high temperatures jumping another 6-8 degrees this afternoon compared to yesterday (Monday) leading to mid to upper 90s across the inland valleys. Due to the offshore flow pattern from the surface to roughly 800mb (~6000ft) facilitating downslope compressional warming off the Cascades, the hottest relative temperatures regionally will most likely be found at the base of the foothills into the eastern Willamette valley.

Then hot conditions peak on Wednesday and Thursday, however, not without a bit of forecast uncertainty from the smoke and haze being pushed west of the Cascades by offshore/easterly flow. Areas with dense wildfire smoke will see high temperatures limited by several degrees. For today at least, models guidance suggests highs will be most limited over the northern Willamette Valley, Columbia River Gorge, Portland/Vancouver metro and Mt. Hood National Forest. Meanwhile, smoke impacts to temperatures over the rest of southwest WA and northwest OR should be minimal (maybe a degree or two) assuming similar fire activity to past days. On Wednesday, the latest RRFS model points to little impact on temperatures due to a more dispersed and thinner smoke layer. Overnight temperatures beginning tonight through at least Wednesday night only bottom out in the upper 50s to mid 60s as well limiting the time period of overnight relief, especially in urban centers. It should quickly be noted smoke has a minimal impact on overnight temperatures, even when thick. But regardless of the exact outcome of our temperatures, conditions will be hot enough to bring an increased risk of heat-related illnesses. As such, various Heat Advisories remain in effect for most inland valleys starting today. 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.

Heading into Friday the axis of the broad upper-level ridge feature meanders further east of western Oregon/southwestern Washington helping to increase onshore flow. That said, there'llwindylikely be enough influence from the high pressure ridge aloft to keep high temperatures in the low 90s across the inland valleys. 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 bringing more appreciable moderation - moderate to high confidence for maximum temperatures returning to the low to mid 80s by Sunday/Monday. -99/23

AVIATION...Through 18Z Wed

Satellite imagery and terminal observations as of late Tuesday morning depicts widespread smoke across northwest Oregon and southwest Washington as winds from the east push wildfire smoke into the area from central/eastern Oregon. Latest PIREPs and METARs suggest that this smoke layer is generally around 5-6 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 5-6 SM for most 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 today 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 increasing this afternoon and weakening tonight. -10

MARINE

Headed into the middle of the week a ridge of high pressure will continue to facilitate Small Craft Advisory northerly winds across the inner and outer waters at times, including the Columbia River Bar. Expect the strongest relative winds during the afternoon and evening hours. The on Thursday the winds at the surface begin to gain a slight westerly component, generally shifting to the northwest. Overall wind speeds will decrease with gusts holding in the 15-20 knot range, highest outer waters, but seas remain relatively similar around 5 to 8 ft at 8-9 seconds and being mostly wind wave/fresh swell driven. -99

FIRE WEATHER...Today through Thursday

Easterly flow continues to increase through the Columbia River Gorge and along the Cascade crest-line down into the foothills early this morning with gusts around 15-30 mph already being observed coupled with fairly poor to moderate relative humidity values (below ~30-40%) as well. These winds are expected to peak midday into the early afternoon, likely strongest in the western Gorge with gusts up to 30-40 mph in the most wind-prone locations (Three Corner Rock). Given further degraded relative humidity values in place after heating gets underway today, critical fire weather conditions capable of rapid fire spread will be possible. Conditions then remain dry and breezy in the western Gorge as easterly winds continue tonight through a good chunk of Wednesday. 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. 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 in the afternoon again. 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

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 11 PM PDT this evening for PZZ210. Small Craft Advisory until 5 AM PDT Wednesday for PZZ251>253- 271>273.