textproduct: Portland

SYNOPSIS

Upper level high pressure continues building over the region, leading to a few days of hot temperatures, warm overnight lows, low humidity, and breezy winds. Peak heating days are today and Monday with minimal overnight temperature relief. Extreme Heat Warning in effect for the Greater Portland- Vancouver Metro and Columbia River Gorge Sunday through Tuesday. Heat Advisory in effect elsewhere, with the coast only being on Sunday. Breezy offshore winds continue through tonight, easing on Monday. Temperatures drop around 10-15 degrees on Tuesday, though remain warm Tuesday through the end of the week for inland locations.

DISCUSSION...Sunday through Saturday

Just as forecast, high pressure has amplified over the far eastern Pacific over the past 24 hours, as has a surface thermal trough over western OR and WA. Peak daytime temperatures on Saturday were right on track with the forecast except for along the coast where temperatures peaked a bit higher than forecast in some locations due to enhanced warming from downslope winds off the western Coast Range. Highs on Saturday were in the upper 80s to low 90s for interior lowlands and anywhere from the 70s to low 80s along the coast. Current temperatures early Sunday are anywhere from 5 to 20 degrees warmer than 24 hours ago with the Coast Range and Cascades seeing the widest range with current temperatures in the upper 60s to low 70s due to a strong surface inversion preventing cooling.

Expect even hotter temperatures today into Monday as the high pressure axis shifts east over the PacNW coast. There is high confidence (70-95+% chance) that temperatures will peak above 95 degrees for most of the interior lowlands as well as portions of the Coast Range each day. Some locations could even exceed 100 degrees, especially on Monday. Best chances today are mainly in a small stretch of area just west of the West Hills to around Aurora at around a 20-45% chance. The area and probabilities expand on Monday from Salem north to Hillsboro at 50-75% chance, though the Portland metro east of the West Hills has only a 30-55% chance, as do the Corvallis area and portions of the Coast Range. Today will be the hottest day for the coast as downsloping offshore winds continue with anywhere from a 50-75% chance of temperatures exceeding 80 degrees along the immediate coast, with higher probabilities in Astoria, Tillamook, Pacific City, and Lincoln City.

Temperatures overnight tonight into Monday morning and again Monday night into Tuesday morning will remain on the warmer side, not allowing much relief from the heat. Tonight is expected to be the warmest with high confidence in locations west of the Cascade foothills, including the coast, remaining above 60 degrees with a moderate confidence (50-65% chance) that temperatures remain above 65 degrees. There's even a 20-35% chance that locations such as the Portland metro area, western Willamette Valley, and central OR Coast Range remain above 70 degrees. For Monday night into Tuesday morning, there's moderate to high confidence the interior lowlands remain above 60 degrees with 35-45% chance the Portland metro area and Eugene area remain above 65 degrees.

The combination of hot daytime temperatures and warm overnight temperatures is producing widespread Moderate to High HeatRisk through Monday for locations west of the Cascades. This means most of the general population will be susceptible to heat- related illness, especially those without access to air conditioning and those spending extended time outdoors. Heat is one of the leading causes of weather-related fatalities, so it is critical to protect yourself and loved ones from the heat by staying hydrated, finding locations with air conditioning, and checking on your neighbors. Also, area waterways are still very cold, so it is vital to wear life vests and remain aware of signs of hypothermia if planning on spending time near lakes and rivers.

In addition to the heat, the tightening surface pressure gradients associated with the surface thermal trough will continue to produce breezy offshore winds today and tonight, especially within the central and southern Willamette Valley in the afternoon and evening hours and the Columbia River Gorge and western Cascade gaps in the overnight hours. Additionally, as daytime temperatures increase, relative humidities will also decrease to near critical levels. This is producing some fire weather concerns in areas with cured grasses and finer fuels into Monday due to hot, dry, and breezy conditions. Based on feedback from area partners, fuels are not quite cured enough to consider any Red Flag Warnings at this point, but there is uncertainty on how the fuels will be impacted by the continuous days of dry and hot conditions. Be aware of potential ignition sources such as vehicle chains dragging on the pavement, hot vehicle components, sparks created by power tools, and cigarette butts as all of these could easily result in the ignition of cured grasses and dry, fine fuels. Live vegetation and larger fuels may not have enough time to dry out prior to the dry and breezy conditions, but this is a variable that is being closely monitored by our State and Federal Fire Partners.

Ensemble guidance is in good agreement in indicating that a shortwave ejecting east into British Columbia off of a low pressure system off the southern Alaska coast will break down the strong high pressure over the West Coast and eastern Pacific as well as the surface thermal trough late Monday into Tuesday. However, weaker high pressure still remains in place on Tuesday. This change will allow for general onshore flow to return, stronger in the northern counties of the CWA, as well as cooler temperatures on Tuesday than the previous two days, though still remaining above normal in the mid to upper 80s for the Willamette Valley and upper 70s for the SW WA lowlands. Heat impacts still remain a concern on Tuesday due to the warmer morning low temperatures an a 60-90% chance of high temperatures remaining above 85 degrees. While the Extreme Heat Warning and Heat Advisories remain in effect through Tuesday, we will continue to evaluate whether the heat remains a significant enough threat for these hazards. An area that will maintain at least Moderate HeatRisk on Tuesday is the greater Portland- Vancouver Metro area and other urban centers, likely due to the urban heat island effect.

General upper level high pressure is slated to remain over the region Wednesday into Thursday according to ensemble guidance with potentially very weak troughing developing late in the week. Despite the weak troughing, conditions are expected to remain warm and dry into next weekend with the potential for morning coastal stratus. In general, expecting temperatures to remain in the 80s for the interior lowlands, 60s along the coast, and 60s to 70s over the terrain. -03/27

AVIATION

High pressure will maintain VFR conditions with clear skies through the TAF period across all terminals. Variable winds around 5 kt or less inland with light offshore winds along the coast. After 14-16z Sun, offshore pressure gradients will tighten and support breezy northerly to northeasterly winds across the region, with gusts up to 20-25 kt at any given terminal. After 01-03z Mon, winds should gradually weaken as pressure gradients ease.

In addition, temperatures between 90 to 100 degrees F are forecast across the Willamette Valley Sunday and Monday. Be aware of high density altitude which may reduce aircraft performance.

KPDX AND APPROACHES...VFR with clear skies through the TAF period. Light northwest winds under 5 kt overnight, turning more east-northeasterly after 15-18z Sun with gusts up to 20-25 kt through the afternoon. Winds weaken in the evening after 01-03z Mon. -10/03

MARINE

High pressure offshore will maintain the summertime pattern this weekend and through much of next week. A strengthening thermal trough along the coast will increase pressure gradients over the coastal waters again today. As such, northerly winds will increase to around 15-25 kt with gusts up to 25-30 kt south of Cape Falcon. Winds ease overnight tonight into Monday morning, but are expected to increase again as diurnally driven northerlies peak each afternoon and evening through next week. Seas around 4 to 8 ft at 7-10 seconds are expected to persist, driven primarily by the northerly wind chop. -DH/03

CLIMATE

Record high temperatures and warm low temperatures for Sunday, June 14

High Temperatures: Warm Low Temperatures: Portland Int'l 89F (1988) 62F (1985) Vancouver, WA 93F (1986) 61F (1931) Hillsboro 96F (1961) 60F (1963) McMinnville 93F (1986) 59F (1936) Salem 92F (1961) 59F (1936) Eugene 92F (1914) 57F (1993) Astoria 86F (1914) 58F (1972)

Record high temperatures and warm low temperatures for Monday, June 15

High Temperatures: Warm Low Temperatures: Portland Int'l 95F (1966) 60F (1969) Vancouver, WA 95F (1930, 1966) 62F (1961) Hillsboro 99F (1961) 60F (1963) McMinnville 96F (1961) 59F (1936) Salem100F (1966) 59F (1931) Eugene 96F (1966) 60F (1961) Astoria 91F (1966) 58F (1997)

Record high temperatures and warm low temperatures for Tuesday, June 16

High Temperatures: Warm Low Temperatures: Portland Int'l 95F (1958) 60F (2012) Vancouver, WA 92F (1961) 67F (1966) Hillsboro100F (1961) 65F (1961) McMinnville 98F (1961) 59F (1966) Salem 97F (1961) 61F (1961) Eugene 95F (1961) 62F (1961) Astoria 87F (1958) 59F (1997)

PQR WATCHES/WARNINGS/ADVISORIES

OR...Heat Advisory from 11 AM this morning to 11 PM PDT this evening for ORZ101>103.

Heat Advisory from 11 AM this morning to 11 PM PDT Tuesday for ORZ104>108-113>119-121>125.

Extreme Heat Warning from 11 AM this morning to 11 PM PDT Tuesday for ORZ109>112-120.

WA...Heat Advisory from 11 AM this morning to 11 PM PDT this evening for WAZ201.

Heat Advisory from 11 AM this morning to 11 PM PDT Tuesday for WAZ202>205-208-210.

Extreme Heat Warning from 11 AM this morning to 11 PM PDT Tuesday for WAZ206-207-209.

PZ...Small Craft Advisory until 5 AM PDT Tuesday for PZZ252-253-272- 273.