textproduct: Portland

SYNOPSIS

Largely dry weather continues into next week as high pressure dominates locally. An upper low meandering off the coast will raise the chances for showers and afternoon thunderstorms today and Saturday, most likely over the Cascades. Unseasonable heat then peaks late this weekend, and those seeking relief in area rivers and lakes should remain aware of cold water hazards and practice water safety. Dry and seasonably warm weather continues into next week.

LONG TERM...Saturday Night through Thursday

Upper-level ridging will build over top the closed low meandering along the California coast, supporting hotter and drier weather on Sunday. As offshore flow begins to develop Saturday night, overnight temperatures may only briefly fall below 60 degrees along the lower Columbia and northern Willamette Valleys early Sunday morning, setting the stage for what will be the warmest day of the year so far. Sunny skies and mid-level temperatures rising to 17-18C at 850 hPa will push temperatures well into the 80s to low 90s within inland valleys, and to the 70s to low 80s elsewhere with the exception of only the immediate coastline. Chances to exceed 90 degrees are the highest near Portland, with 75-95% chances across the metro area, and lower to the north and south: 15-25% in the Lewis and Cowlitz Valleys of southwest Washington, 25-45% in the central Willamette Valley including Salem and McMinnville, and 10-25% in the southern Willamette Valley. If Portland International Airport does reach 90 degrees, as is expected, this would represent the second-earliest 90 degree reading on record, surpassed only by April 30, 1998. Daily record high temperatures appear likely at climate sites across the region, in some cases breaking previous records by more than 5 degrees. See the Climate section below for additional information on potential record high temperatures.

During this late-weekend warmth, those seeking relief from heat in area 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. Moderate HeatRisk across the northern Willamette Valley, Portland/Vancouver metro, Lower Columbia Valley, and Columbia Gorge on Sunday may also affect those who are sensitive to heat.

By the beginning of the workweek, ensemble guidance continues to favor moderating temperatures as the upper ridge axis moves inland. A southerly wind reversal will increase marine stratus coverage along the coast, with broader onshore flow cooling inland areas as well. There is general consensus in dry conditions across most of the region, however a minority of ensemble members depict very light rain or drizzle within the shallow marine layer, most likely in the overnight hours. -36

AVIATION

Latest satellite imagery continues to depict marine stratus slowly pushing inland along the coast, resulting in marginal IFR/MVFR cigs at coastal terminals. Moderate to high confidence (70-90% chance) of high-end IFR persisting through 18-22z Fri, with the highest chances for the most persistent restricted cigs to the south toward KONP. Cloud coverage remains lower along the north OR/south WA coast including at KAST, but IFR cigs remain the most likely. Chances for LIFR cigs below 500 ft have decreased to 10-30% along the coast, increasing to the south. North to northwest winds continue through the period around 5 kt this morning, building to 10-15 kt with gusts to 20 kt this afternoon, then easing below 10 kt again this evening.

Inland, VFR conditions continue beneath increasing high clouds at 20-25 kft, however southern Willamette Valley terminals may yet see periods of MVFR cigs early this morning, with 50-60% chances for cigs of 2-3 kft at KEUG if marine stratus is able to push inland through the Coast Range. Chances are lower, 20-40%, farther north in the Willamette Valley (KCVO, KSLE, KUAO), and 10% or less at Portland area terminals. Otherwise, expect slowly lowering cigs down to 6-10 kft by 00-06z Sat, with 25-30% chances for showers or possibly thunderstorms late in the period. These showers or storms are most likely to develop over the Cascades and track northward, resulting in increasing chances heading east from the Willamette River. The location and timing of any showers is uncertain, and impacts to terminals remain very low confidence. Light winds this morning will build out of the northwest to 5-10 kt this afternoon, then ease below 5 kt again this evening.

KPDX AND APPROACHES...VFR flying conditions beneath increasing high clouds expected through the period, with cigs falling from 20-25 kft early this morning to near 10 kft by this evening. Very low chances (less than 10%) for MVFR cigs within marine stratus early this morning. Chances for rain showers increase to 15-20% late in the period, after 06z Sat, with very low confidence in any terminal impacts. Northwest winds continue through the period, increasing to 5-10 kt this afternoon before easing below 5 kt again this evening. -36

MARINE

High pressure offshore will maintain northerly flow through Sunday. The strongest winds this afternoon and evening as diurnal pressure gradients tighten, yielding gusts of 20-25 kt, most likely beyond 20 NM and south of Cape Falcon. Small Craft Advisories remain in effect in these areas, expanding to include the outer waters offshore of the mouth of the Columbia River and inner waters south of Cape Falcon after 2 PM today. As winds ease tonight, gusts will fall below 20 kt in these areas by 2 AM Saturday, and in the outer waters south of Cape Falcon by 8 AM Saturday. Elsewhere within 10 NM north of Cape Falcon including the Columbia River Bar, isolated gusts over 20 kt are expected, but the duration and frequency does not merit a Small Craft Advisory at this time. Seas will remain around 5-8 ft with a mid-period northwesterly swell of 5-6 ft at 12-14 seconds lengthening to 14-16 seconds this weekend. This long-period swell will support a moderate sneaker wave threat at area beaches, and those participating in razor clam digs or other coastal recreation should take extra precautions.

Strong currents continue during morning ebb tides across the Columbia River Bar through Sunday. A Small Craft Advisory remains in effect through 8 AM today due to steep seas of 6-7 ft during the peak ebb tide. Additional Advisories may be needed Saturday and Sunday mornings for subsequent strong ebbs, however seas falling below 7 ft may preclude this.

A wind reversal on Monday will see southerly to southwesterly flow develop early next week with increased low marine stratus and overnight drizzle or light rain. More seasonable northerly flow redevelops in the latter half of the week with persistent seas of 4-7 ft. -36

CLIMATE

Daily record high temperatures for Sunday, May 3:

LocationForecastRecord (Year)

Astoria7581 (1992, 1944) Vancouver8984 (1944) Portland Int'l9289 (1992) Hillsboro9082 (2017) McMinnville8787 (1992) Salem8986 (1992) Eugene8583 (1944)

PQR WATCHES/WARNINGS/ADVISORIES

OR...None.

WA...None.

PZ...Small Craft Advisory from 2 PM this afternoon to 2 AM PDT Saturday for PZZ252-253-271.

Small Craft Advisory until 8 AM PDT Saturday for PZZ272-273.