textproduct: Portland

SYNOPSIS

Conditions gradually become warmer the remainder of the week culminating in a period of abnormally hot conditions on Sunday and Monday - an Extreme Heat Watch is in effect for the greater Portland/Vancouver Metro, western Columbia Gorge, central Willamette Valley, and portions of the lower Columbia. This time period will present some of the hottest temperatures we've seen so far this year. Confidence is high (80-90%) closer to normal temperatures (70s to near 80 degrees) return by Wednesday of next week.

UPDATE

The Extreme Heat Watch over the Portland/Vancouver metro and western Columbia River Gorge has been expanded to include the central Willamette Valley, West Hills, Chehalem Mountains, and portions of the lower Columbia. This is in response to a slight uptick in forecast temperatures Sunday night into Monday. The 06Z/June 10 iteration of the GEFS has trended temperatures slightly upward on Monday, June 15. The EURO ensemble remains relatively cooler than the GEFS, but only by a few degrees. Meanwhile, the latest iteration of the deterministic NBM has ticked up a couple degrees, and is now showing high temperatures in the upper 90s to 100 degrees for most locations within the Extreme Heat Watch. As such, the aforementioned zones have a Major HeatRisk. -23

LONG TERM...Saturday through Wednesday

This weekend into early next week our focus remains on heat related impacts as there remains good confidence we'll likely experience the hottest temperatures of 2026 thus far. Both deterministic and ensemble guidance are in excellent agreement showing the upper- level ridge over the eastern Pacific slowly meandering towards the Pacific northwest. Saturday is when temperatures make their next large jump higher into the mid to upper 80s across the inland valleys. The latest NBM probabilities for daytime highs above 90 degrees F have lowered compared to prior runs, generally in the 10-40% range for the Willamette Valley. Then come Sunday and Monday temperatures are expected to peak in the 90s - highest on Monday. NBM probabilities for max temperatures at or above 95 degrees are 20-65% on Saturday, highest in the north Willamette Valley through the Portland Metro. These same probabilities to exceed 95 degrees peak on Sunday around 45-90%, again highest in the Willamette Valley into the Portland Metro. It's worth noting we'll still have a chance to meet or exceed 100 degrees on Monday, mainly Salem through Portland, with probabilities around 30-40%. Overnight low temperatures only drop into the low to mid 60s across the inland valleys both Sunday night and Monday night keeping of the window of relief from the hot daytime highs rather limited.

As far as Major HeatRisk is concerned, there is a 55-80% probability to hit this category on Sunday and a 25-80% probability on Monday (highest Portland Metro, lowest near Eugene and along the coast). At least through this period the probability for Extreme HeatRisk across the region is only 5-15% or less. Anyone who is sensitive to heat or those who have outdoor plans should prepare for and takes steps to mitigate potential heat impacts. For those planning to seek relief by swimming in local area rivers and/or lakes to cool off, be mindful of cold water temperatures and swift currents which can become life threatening if precautions like wearing a life preserver is not taken.

Given this upper level pattern progression, a thermally induced surface trough also will establish itself somewhere west of the Cascade Crest-line which could result in locally breezy winds within the Cascades gaps and/or the Willamette Valley depending on its orientation. As daytime highs increase, relative humidities will also decrease. Therefore, with conditions drying out AND the potential for breezy winds, there are increasing fire weather concerns over the weekend through the start of next week. So, be aware of potential ignition sources such as chains dragging on the pavement, hot vehicle components, as well as cigarette butts as these could easily result in the ignition of dry, fine fuels. Live vegetation and larger fuels may not have the time to dry out, but this is a variable that is being closely monitored by our State and Federal Fire Partners.

Fortunately the heat won't last forever. Come Tuesday and Wednesday (June 16/17th), ensemble modeling systems do depict the ridge finally breaking down and shifting eastward bringing a return of relatively cooler westerly flow. However, there's still a notable amount uncertainty as to whether this transition takes place on Tuesday or if it holds off until Wednesday. But at least the majority of models do push temperatures downward back into the 70s or low 80s by the middle of next week as in general the NBM 25th-75th percentiles fall within these values. The latest NBM only gives the inland valleys a 5-15% chance for highs to exceed 90 degrees F on Wednesday. So, confidence remains high for closer to normal daytime highs to return by the middle of next week. -99/42

AVIATION

Largely VFR flying conditions expected across the airspace through the period. Widely isolated rain showers continue north of US-20, but terminal impacts are unlikely before any remaining showers end by 00z Thu. Some low clouds continue to yield 20-40% chances of MVFR cigs at all terminals before skies trend clearer by 21-24z Wed as high pressure continues to build offshore. Northwest winds of 5-10 kt continue across the airspace, easing below 5 kt after 06-12z Thu. There are 15-35% chances for low stratus and MVFR cigs to develop overnight, most likely along the east side of the Willamette Valley. Any light offshore winds will inhibit low cloud formation along the coast.

KPDX AND APPROACHES...VFR conditions expected throughout the period. Lingering low clouds this morning with widely isolated rain showers are unlikely to cause terminal impacts. Skies trend clearer through the day with continued northwest winds around 5 kt. Winds ease overnight with low (15-20%) chances for MVFR cigs after 12z Thu. -36

MARINE..Seas continue to subside early this morning with bouy observations showing wave heights around 6-8 ft at ~10 seconds, likely ending up closer 5-6ft at 10 seconds but the end of the day. From here our focus shifts to high pressure building offshore through the remainder of the week into the weekend. This will allow WNW winds to shift northerly this evening into tonight followed by a fairly typical summer-time north wind pattern going forward. Expect gusts up to 20-28 kt each afternoon and evening from Thursday through the weekend - highest gusts generally over the outer waters and south of Cape Falcon. During this period of time, wave heights hold between 4-7ft at 9 to 10 seconds. This may necessitate daily Small Craft Advisories through Monday, potentially longer. -99

PQR WATCHES/WARNINGS/ADVISORIES

OR...Extreme Heat Watch from Sunday morning through Tuesday evening for ORZ108>115-120.

WA...Extreme Heat Watch from Sunday morning through Tuesday evening for WAZ206-207-209.

PZ...None.