textproduct: Portland

SYNOPSIS

Temperatures rebound on Monday and Tuesday as high pressure re-builds, with the warmest temperatures on Tuesday. Precipitation chances return on Wednesday as a trough approaches the West Coast. Another low from the Gulf of Alaska will maintain precipitation chances and a trend towards cooler temperatures through the end of the week.

DISCUSSION...Today through Sunday

Looking at the first part of the week, deterministic and ensemble guidance remain in agreement with upper-level ridging re-building over the Pacific Northwest. This will result in a return of sunny skies while dry weather prevails. There is high confidence that daytime high temperatures along the coast will be in the mid 60s to mid 70s, low 70s to low 80s for the Cascades and mid 70s to low 80s for the Willamette Valley. Tuesday is looking to be the hottest day of the week with daytime highs along the coast in the mid 60s to mid 70s, mid 70s to mid 80s for the Cascades and low 80s to upper 80s for the Willamette Valley. There is currently a 20-40% chance that high temperatures exceed 90 degrees on Tuesday across the Portland/Vancouver Metro Area. The rest of the Willamette Valley, southwest Washington lowlands, Columbia River Gorge, and Upper Hood River Valley have a 5-10% chance of exceeding 90 degrees. If KPDX (Portland Airport) ends up at or above 90 degrees, this would tie or break the daily record of 90 degrees which was set in 2023. Given the warmer forecast temperatures on Tuesday, there is now Moderate HeatRisk across the Portland/Vancouver Metro Area, Cowlitz Valley, and Columbia River Gorge. Those who are sensitive to heat will be affected, especially those without cooling and hydration.

The next chances for precipitation return late Tuesday/Wednesday as the next trough approaches the West Coast. The majority (80%) of ensemble members show an upper level trough tracking over Oregon and as a result, chances for precipitation increases across our CWA towards 25-45%. However, current QPF forecasts remain around a few hundredths of an inch, if any. In addition, southerly/southeasterly flow from this pattern would bring increased mid-level moisture and instability, bringing a 15-25% chance for thunderstorms across the Linn and Lane County Cascades Tuesday and Wednesday afternoon. This pattern would also bring about cooler daytime highs through the latter part of the week. The other scenario depicted by the remaining (20%) ensemble members have a closed low aimed at Central California which would decrease precipitation chances as well as result in warmer daytime temperatures.

There is greater uncertainty in the pattern Thursday-Saturday, however, most ensemble members are showing another trough dipping down from the Gulf of Alaska by the end of the week. This will maintain chances for precipitation across the area and bring lower 500 mb heights, resulting in temperatures cooling down to seasonal normals. However, the exact track of this system, timing, and precipitation amounts are still uncertain. About 30% of ensemble members have ridging re-building by the weekend. /42-10

AVIATION

Dry southwesterly flow aloft, with north/northwest flow at the surface continues as upper level ridging builds over the region today. Expect predominately VFR conditions for the majority of the airspace. The only exception is a 40-60% chance for the redevelopment of MVFR/IFR ceilings around and south of KONP after 10- 12z Tue. Elevated north/northwest surface winds around 10 kts. Gusts along the coast up to 25 kt from 19Z Mon through 03Z Tue. Winds decrease below 7 kts after 04-06z Tue.

KPDX AND APPROACHES... VFR conditions expected through the period. North to northwesterly winds around 8-10 kts, decreasing below 6 kts by 04-06z Tue. -03

MARINE

Weak, upper level high pressure returns across all waters today which will maintain northerly winds. Daytime heating will increase the surface pressure gradient which will result in gusts up to 25 kt for all inner and outer marine zones starting at noon today through early Tuesday morning, granted zones will come on-line and go off-line at various times. Looking towards Tuesday through at least Thursday conditions return to a more benign pattern with north to west winds, with gusts below 20 kt and seas 5 to 7 ft. /42

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory from 5 PM this afternoon to 11 PM PDT this evening for PZZ251-271.

Small Craft Advisory from noon today to 2 AM PDT Tuesday for PZZ252-253-272-273.