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 Portland Metro and western Columbia Gorge. This time period will present some of the hottest temperatures we've seen so far this year. At least confidence is high (80-90%) closer to normal temperatures (70s to near 80) return by Wednesday of next week and a welcome development.

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

Conditions are generally MVFR along the coast and VFR inland early this morning with shower activity still lingering along the coast and in southwest Washington. These showers gradually decrease this morning with the return of mostly dry weather during the afternoon hours. Still, probabilities for MVFR CIGs/VIS along the coast remain around 40-50% until 15-17z after which point predominately VFR conditions are favored. High pressure building overhead likely leads to increasing cloud breaks and scattered high clouds by the evening. Winds generally stay light and less than 5-10 knots most hours at all sites.

KPDX AND APPROACHES...Predominately VFR conditions through the TAF period. However, there is ~20-30% chance for high-end MVFR CIGs (~2.5-3kft) until 16-17z. Any lingering showers should mainly hold north of the terminal with much higher confidence in completely dry weather this afternoon. High-end VFR CIGs scatter out after 00-03z Thu. -99

PQR WATCHES/WARNINGS/ADVISORIES

OR...Extreme Heat Watch from Sunday morning through Monday evening for ORZ109-111-112-120. WA...Extreme Heat Watch from Sunday morning through Monday evening for WAZ206-207-209. PZ...None.