textproduct: Portland

SYNOPSIS

The upper level ridge is building over the region which will lead to a few days of hot temperatures, warm overnight lows, low humidity, and breezy winds. Peak heating days will be Sunday 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 easterly winds through the Columbia River Gorge on this afternoon and Sunday will ease on Monday. Warm conditions remain through the week though will be at least 10 degrees cooler for inland locations.

SHORT TERM...Now through Monday Night

The ridge is beginning to build in and we are already starting to see impacts. As the ridge amplifies, we will see winds and temperatures increase, and humidity drop. There has been minimal change in the overall forecast and all appears to be on track based on current observations. The easterly winds have begun to increase within the Columbia River Gorge and the Portland-Vancouver Metro area. Within an hour, we saw the temperature spike by 87 degrees F, and the humidity drop to 19%. These easterly winds will aid in increasing temperatures this We still cannot rule out high temperatures of 100 degrees F on both Sunday and Monday. Afternoon as they mix down warmer air aloft and warm the surface for inland valleys. We will also see conditions along the coast warm up as those same easterly winds aloft rise up and over the Coast Range, and thus downslope warm air aloft into the coastal cities. Tillamook is a site most known for seeing this effect.

On Sunday and Monday we will see temperatures increase a few degrees each day. We are expecting the warmest day along the coast on Sunday, while the hottest day inland will be on Monday (though only by one or two degrees). Ultimately the pattern will remain generally unchanged on Sunday and Monday. Lets dive into the numbers! There is high confidence that we will see inland highs of 95 degrees F or more but we cannot rule out high temperatures of 100 degrees F or more on both days. On Sunday, the chances are highest in the central Willamette Valley and along the 99W corridor through Tigard into North Plains. The probabilities are a bit more scattered, but in general there is around a 30-40% chance of highs of 100 degrees or more on Sunday. Monday on the other had sees much more widespread probability. One reason for this is that the overnight temperature on Sunday into Monday morning will remain elevated and thus, the daytime temperatures will have a leg up for becoming excessively hot for the region. The latest NBM shows probability ranging from 80-90% within Clackamas and Washington Counties, around 30-50% chance in the Portland-Vancouver Metro, and around 60-70% chance in the central Willamette Valley. Due to more of a northerly wind pattern, the southern Willamette Valley and associated Cascade foothills will see lower probabilities. One thing to consider though is topography. In areas that are east-west aligned, they will see more of that gap flow and warming from the easterly winds. Therefore, they could be slightly warmer.

As previously mentioned, the overnight lows are a very influential component of the forecast as they set the stage for the daytime outcomes. Overall, there is around a 30% chance of low temperatures of 70 degrees or greater Sunday into Monday for the east slopes of the Coast Range and the I-5 corridor. Conditions will be slightly cooler on Monday night into Tuesday where those probabilities are less than 10% everywhere except the far southern Willamette Valley. The combination of the overnight and daytime temperatures is what determines the HeatRisk for the region. On Sunday there has been an expansion of the Major HeatRisk, likely due to the overnight temperatures. On Monday, Major HeatRisk remains just for the Greater Portland-Vancouver Metro area. Elsewhere, Moderate HeatRisk. A number of heat related hazards have been issued.

Because heat is one of the leading cause of weather related deaths, it is critical that you protect yourself, loved ones, pets and community members. Be sure to drink ample water, find cool places to spend your days, and check on your neighbors. In addition, natural water bodies remain quite cold so if you're planning on hitting lakes and rivers to cool down keep that in mind. Cold Water Shock can hit quickly and sometimes without signs.

In addition to the heat, the tightening surface pressure gradients associated with the surface thermal trough will lead to breezy offshore winds today and Sunday, 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 evening and 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 Saturday 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. -27/03

LONG TERM...Tuesday through Saturday

Models are coming into better agreement that the ridge will hold into Tuesday and the trough that was displayed earlier in the week is no longer going to have significant influence. It will still cause the ridge to flatten slightly, but we are not necessarily expecting straight zonal flow. Instead, we will see a slight northwesterly wind which will keep the northern portions of the area cooler than the southern areas. With this in mind though, heat remains a concern though the daytime highs continue to remain below critical levels. While the Extreme Heat Warning and Heat Advisories remain in effect through Tuesday, we will continue to evaluate on whether they remain a significant threat. An area that will maintain at least Moderate HeatRisk on Tuesday is the greater Portland-Vancouver Metro area and other urban centers. This is likely due to the urban heat island effect.

Come Wednesday we will have transitioned out of the heat wave but 500 mb ensemble models continue to show general ridging over the region. This means that we will continue to see dry, clear, and warm conditions. Overall, high temperatures will be in the 60s along the coast, in the 80s inland, and in the 60s-70s along the Cascades. The pattern remains fairly stable with minimal changes in the sensible weather. Ultimately it just comes down to the numbers and how much uncertainty we experience. As we move into later on the week (Thu-Fri), confidence decreases in exact temperature values. Right now there is anywhere from a 6-10 degree spread in potential high temperatures each day. Ultimately prepare for a week of dry and warm conditions. -27

AVIATION

High pressure will maintain VFR conditions with clear skies through the TAF period across all terminals. Tonight, 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 16-18z Sun with gusts up to 20-25 kt through the afternoon. Winds weaken in the evening after 01-02z Mon. -10

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)

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 today. As such, northerly winds will increase to around 15-25 kt with gusts up to 25-30 kt south of Cape Falcon, while gusts up to 25 kt will be possible northward toward Cape Disappointment. Winds ease by Sunday 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

PQR WATCHES/WARNINGS/ADVISORIES

OR...Heat Advisory from 11 AM to 11 PM PDT Sunday for ORZ101>103.

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

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

WA...Heat Advisory from 11 AM to 11 PM PDT Sunday for WAZ201.

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

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

PZ...Small Craft Advisory until 2 AM PDT Sunday for PZZ251-271.

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