textproduct: Portland

SYNOPSIS

Warm and mostly dry weather is expected through the upcoming weekend as high pressure builds over the region. Afternoon temperatures warm into the 70s to near 80 degrees on Thursday, cooling off slightly on Friday. An upper level low offshore drifts south toward the central California coast through the weekend, drawing wrap around moisture across the Oregon Cascades, increasing the chances for showers and possibly thunder. Sunday is expected to be the warmest day, with highs warming into the 80s, and potentially reaching 90 degrees in the Portland Metro. With warm and dry conditions this weekend, keep cold water safety in mind as local rivers remain cold enough for cold water shock.

DISCUSSION...Tonight through Wednesday

A warming trend is underway as a ridge of high pressure over the NE Pacific shifts east across the Pacific NW. Afternoon temperatures today are expected to run a few degrees above normal with overnight lows cooling back into the 40s. A weak upper shortwave trough will bring some mid to high level clouds across the area on Thursday, but with the ridge axis building over the region, light offshore winds, and 850 mb temperatures increasing to around 10-12 C, expect afternoon high temps on Thursday to warm into at least 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 (30-50%). This would be the first 80 degree day of 2026 for PDX 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 of thunder, mainly south of Mt. Hood near the Cascade crest. The flow aloft turns more southeasterly on Saturday with slightly higher PoPs over the Cascades and up to 20% chance of thunder. There is more spread in potential afternoon temperatures Friday and Saturday as it will depend on cloud coverage, as high temps could range anywhere from the lower-to-mid 70s to lower 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 C. There is high confidence that Sunday will be the warmest day of the week. In fact, there is around a 50-70% 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 PDX was April 20, 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 of thunder, while easterly flow aloft spreads lower chances of showers (15-30%) and thunder (10-15%) across the southern Willamette Valley, including Eugene. Temperatures are likely to be a bit cooler there if clouds and/or precip do manifest.

During this late-week warmth, those recreating on area rivers should remain aware of water temperatures, which remain cold enough for cold water shock, even on hot afternoons. Wear a personal floatation device and use extra caution around fast, cold water.

Ensembles and the clusters continue to show some form of the rex block persisting into early next week. But, uncertainty increases through the middle of next week with the details. Conditions likely remain dry for most areas, while temperatures remain seasonably warm, though are most likely to cool back somewhere into the lower 70s to lower 80s. A southerly wind reversal may push marine stratus back up the coast and potentially inland by Monday morning. /DH

AVIATION

High pressure continues to build over the airspace, this will support VFR conditions under mostly clear skies for the majority of the airspace. The exceptions will be for KAST, KONP, KEUG and KSLE. These locations have a 10-25% chance of developing IFR/LIFR conditions starting around 10Z-12Z Thursday as low level stratus or fog could develop, with KONP having the highest chance of developing these lowered flight conditions. Any lowered flight conditions are expected to dissipate starting around 17Z-19Z Thursday. Afterwards, VFR conditions will dominate across the airspace. Northerly winds will become light and variable through the overnight hours and become northerly again around 18Z Thursday. KPDX and KTTD will also develop more easterly winds with gusts up to 20 kt expected to impact KTTD starting around 19Z-21Z Thursday.

KPDX AND APPROACHES...VFR under mostly clear skies will persist through the TAF period. Generally northerly winds will become light and variable through 08Z Thursday. North to northeast winds return around 19Z-21Z Thursday. /42

MARINE

High pressure offshore will continue to support northerly winds across the waters through the end of the week. Winds will strengthen each afternoon and evening as pressure gradients tighten over the coastal waters. Winds continue to strengthen late this afternoon, beginning to bring gusts around 20-25 kt to the waters south of Cape Falcon. Today through at least 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 Thursday afternoon through at least early Friday. A Small Craft Advisory for the waters south of Cape Falcon will remain in effect until early Friday morning. A Small Craft Advisory for the Columbia River Bar will also go into effect for a strong ebb current between 2-7 AM Thursday. Lastly, a Small Craft Advisory for the waters north of Cape Falcon has been issued from 11 AM Thursday to 5 AM Friday.

Seas of 6 to 8 ft are expected to persist through the week with a northwesterly swell. Mid-period swells of 12-15 seconds may result in a moderate sneaker wave threat at beaches through Friday. Another moderate sneaker wave threat arrives on Sunday. Those participating in razor clam digs and beach recreational activities should take extra precaution.~12/10

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory from 2 AM to 7 AM PDT Thursday for PZZ210.

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

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