textproduct: Portland

SYNOPSIS

Warm and mostly dry weather is expected through the upcoming weekend as high pressure builds over the region. An upper level low near California will bring wrap around moisture into Oregon, increasing the chances for showers and thunderstorms across the Cascades. Sunday is expected to be the warmest day, with highs warming into the 80s, and potentially 90 degrees in the Portland/Vancouver Metro. Those seeking relief from heat in rivers and lakes should make sure to practice water safety and wear a personal flotation device.

DISCUSSION...Today through Wednesday

Satellite imagery as of early Thursday morning depicts marine stratus along the coast while inland locations remain mostly clear with a few high clouds from a weak upper level shortwave trough. Later today, upper-level ridging amplifying overhead will maintain dry weather, light offshore winds, and temperatures increasing into the mid to upper 70s. The Portland/Vancouver metro has the highest chances (80-90%) for reaching 80 degrees on Thursday, while the remainder of the I-5 corridor is lower (20-40%). This would be the first 80 degree day of 2026 for KPDX if it were to occur. The average first 80 degree day is around May 7th. On Friday, guidance continues to show the upper ridge shifting east as an upper trough develops into a cutoff low offshore, which then drifts south on Saturday. Mid-level moisture and southerly flow aloft will allow for increasing chances of showers over the Cascades and foothills later Friday afternoon, along with a slight (15%) chance for thunderstorms, mainly south of Mt. Hood. The flow aloft turns more southeasterly on Saturday with slightly higher chances for showers over the Cascades and up to a 20% chance for thunderstorms. There is more spread in potential afternoon temperatures on Saturday as it will depend on cloud coverage, as high temps could range anywhere from the lower-to-mid 70s to low 80s. Winds also turn back onshore Friday afternoon bringing more moderated pacific air.

By Sunday, ensemble guidance depicts the upper closed low located most likely off the coast of central California, while upper level ridging rebuilds into the Pacific NW, setting up a rex block pattern. Ensemble guidance also suggests 850 mb temperatures rise again to around 14-17 degrees C. There is high confidence that Sunday will be the warmest day of the week (and year so far). In fact, there is around a 60-80% chance that temperatures exceed 90 degrees across parts of the Portland/Vancouver metro. If PDX reaches 90 degrees on Sunday (May 3rd), it would be the second earliest 90 degree temp of the season at the airport (the earliest recorded 90F at KPDX was April 30, 1998). There is more uncertainty in the forecast across southern parts of the forecast area, in part due to the positioning of the upper low and how far north the wrap around moisture surges. Showers are now likely for the Lane County Cascades, along with a 20% chance for thunderstorms, while easterly flow aloft spreads lower chances of showers (15-30%) and thunderstorms (10-15%) across the southern Willamette Valley, including Eugene. Temperatures are likely to be a few degrees cooler there if clouds and/or showers do manifest.

During this late-week warmth, those seeking relief from heat in rivers and lakes may be exposed to water hazards such as swift currents and/or cold water, both of which can be life- threatening. Make sure to practice water safety and wear a personal flotation device.

Ensembles and the clusters continue to show some form of the rex block persisting into early next week with full-scale ridging returning by mid-week as the low over California shifts eastward. Conditions likely remain dry for most areas, while temperatures remain seasonably warm, though are most likely to cool back somewhere into the low to mid 70s. A southerly wind reversal may push marine stratus back up the coast and potentially inland by Monday morning. -10/DH

AVIATION

Satellite imagery as of early Thursday morning depicts marine stratus along the coast bringing IFR conditions to KAST and KONP. Expect IFR conditions to continue throughout the morning before breaking out and returning VFR conditions after 17-18z Thu. Meanwhile, inland terminals remain VFR throughout the TAF period with FEW/SCT high clouds. Winds generally northwesterly along the coast, breeziest in the afternoon with gusts up to 20 kt between 21z Thu-02z Fri when pressure gradients are tightest. For inland locations, winds remain north-northeasterly and under 10 kt. Tonight after 06z Fri, there is a 50-70% chance at any given hour for a return of IFR/MVFR marine stratus along the coast, with the highest chances at KONP.

KPDX AND APPROACHES...VFR conditions with FEW/SCT high clouds through the TAF period. Variable winds under 5 kt through this morning. Winds turn north-northeasterly after 18z and increase to around 7-9 kt. -10

MARINE

High pressure offshore will continue to support northerly winds across the waters through the weekend. Winds will strengthen each afternoon and evening as pressure gradients tighten over the coastal waters. Today through Friday, there is high confidence (70-90% chance) for at least occasional Small Craft wind gusts up to 20-25 kt. While the strongest gusts will mainly be south of Cape Falcon through Friday, Small Craft winds and seas may spread north of Cape Falcon this afternoon through at least early Friday. Small Craft Advisories remain in effect for the inner waters south of Cape Falcon (0-10 NM offshore) and the waters north of Cape Falcon from this afternoon to early Friday morning, while the Small Craft Advisories for the outer waters south of Cape Falcon (beyond 10 NM offshore) remain in effect through early Saturday morning. In addition, Small Craft Advisories are in effect for the Columbia River Bar between 2-7 AM this morning and 3-8 AM Friday due to strong ebb currents.

Seas of 6 to 8 ft are expected to persist through the week with a northwesterly swell. Mid-period swells of 12-15 seconds will result in a moderate sneaker wave threat at beaches through at least Friday. Swell periods increase to 15-19 sec over the weekend, continuing the moderate sneaker wave threat. Those participating in razor clam digs and beach recreational activities should take extra precaution. -10/12

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 7 AM PDT this morning for PZZ210.

Small Craft Advisory from 3 AM to 8 AM PDT Friday for PZZ210.

Small Craft Advisory from 11 AM this morning to 5 AM PDT Friday for PZZ251-271.

Small Craft Advisory until 5 AM PDT Friday for PZZ252-253.

Small Craft Advisory until 5 AM PDT Saturday for PZZ272-273.