textproduct: Portland

SYNOPSIS

Hot temperatures remains the main story today with an Extreme Heat Warning and Heat Advisories remaining in effect. Conditions ease somewhat Tuesday as onshore flow returns, though inland areas will remain warmer than normal through the upcoming week.

DISCUSSION...Monday through Sunday

As expected, Sunday was a hot day across NW OR and SW WA with many high temperature records broken or tied. Temperatures peaked in the mid to upper 90s for the interior lowlands, low to mid 90s along the Coast Range, and upper 80s to low 90s along the coast. The hot airmass remains in place as upper level high pressure persists over the region, bringing another day of well above normal temperatures today. Temperature observations at 1 AM PDT show mild temperatures. Many locations, such as the Portland metro, the western side of the Willamette Valley, the Coast Range, and the Cascade foothills remain in the 70s. Locations outside of urban heat islands, elevated north winds, or subsidence inversions have fallen into the 60s and even 50s, mainly along the coast and high Cascades. There are still a few more hours of cooling to be had this morning, but temperatures in these areas will still remain fairly oppressive heading into another very hot day. With low temperatures warmer than yesterday, this could allow for daytime temperatures to rise even higher than yesterday for locations east of the coast. Interior lowlands are expected to rise into the upper 90s with a 40-70% chance of temperatures reaching or exceeding 100 degrees for the western Portland metro and northern Willamette Valley from Hillsboro to Salem. The coast is expected to be cooler than yesterday, peaking in the 70s to low 80s. This is because the surface thermal trough that caused the breezy offshore/downsloping winds that enhanced temperatures along the coast is beginning to diminish, continuing through the day. This will cause winds inland and along the coast to turn from east/northeast to northwest, allowing for cooler marine air to impact the coast. One thing to note that could potentially impact inland temperatures is high clouds initiated by a shortwave moving through British Columbia will stream over the area today. Depending on how thick these clouds are, it could prevent temperatures from rising quite as hot as expected, though still expect temperatures to be at least as hot as yesterday. However, the clouds could also keep temperatures early this morning on the warmer side as the clouds could act as an insulator.

Either way, the heat will remain oppressive, especially in locations that do not cool below 65-70 degrees this morning. Moderate to Major HeatRisk remains over the region west of the Cascades, meaning heat-related illness becomes more likely, particularly for those without effective cooling, sensitive groups, and anyone spending prolonged time outdoors. Continue to prioritize heat safety: stay hydrated, limit strenuous afternoon activity, use air- conditioned spaces when possible, and check on vulnerable neighbors, family, and pets. Also remember rivers and lakes remain cold despite the hot weather, increasing the risk of cold-water shock for anyone seeking relief near the water.

Another shortwave moving through British Columbia late tonight into Tuesday will weaken the high pressure over the PacNW (though the axis remains over the E Pacific) and break down the surface thermal trough. This will allow for the return of onshore flow and lower temperatures Tuesday into Wednesday, a brief respite from the extreme heat. However, temperatures for the interior lowlands will still remain above normal (which is around 73-75 degrees) in the 80s. Probabilities for temperatures reaching 90 degrees Tuesday are now less than 10-20% and nearly zero for Wednesday.

Ensemble guidance is now in very good agreement that transient high pressure builds back over the PacNW Thursday as weak troughing develops over the Pacific. This high pressure is expected to warm temperatures to around 90 degrees on Thursday with a 40-65% chance between Salem and Portland. The trough will move inland sometime Friday into Saturday, and will have little impact except for lowering temperatures back into the low to mid 80s for the weekend. Friday is a little more uncertain and could remain on the warmer side with similar probabilities of reaching 90 degrees as Thursday. No significant cool down or precipitation signal is evident in the extended forecast at this time. -03

AVIATION

High pressure will maintain VFR conditions through the TAF period with see increasing high clouds. East to northeast winds shift northwesterly around 16-18z Mon. Winds will increase around this time to 8-12 kts along the coast and southern Willamette Valley with gusts up to 20-25 kts along the coast. North of this, winds increase to 8-12 kts after 21z Mon.

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

KPDX AND APPROACHES...VFR with increasing high clouds through the TAF period. Variable winds under 5 kt tonight, becoming northwesterly 8-10 kt after 18-21z Mon. -03

MARINE

High pressure offshore will maintain the summertime pattern this weekend and through much of next week. Diurnally driven northerlies are expected to peak each afternoon and evening through next week. Lighter north winds this morning will increase to gusts up to 25 kts south of Cape Falcon, then easing overnight into Tuesday morning. Winds then increase across all of the waters Tuesday afternoon and evening, with this pattern continuing into late week. Seas around 4 to 7 ft at 7-10 seconds are expected to persist through Tuesday, driven primarily by the northerly wind chop. Seas are expected to build to around 8 to 10 ft Wednesday into later in the week as a fresh northwesterly swell builds across the waters. /DH/03

CLIMATE

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)

PQR WATCHES/WARNINGS/ADVISORIES

OR...Heat Advisory until 11 PM PDT Tuesday for ORZ104>108-113>119- 121>125.

Extreme Heat Warning until 11 PM PDT Tuesday for ORZ109>112-120.

WA...Heat Advisory until 11 PM PDT Tuesday for WAZ202>205-208-210.

Extreme Heat Warning until 11 PM PDT Tuesday for WAZ206-207-209.

PZ...Small Craft Advisory until 7 AM PDT this morning for PZZ210.

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