textproduct: Portland

SYNOPSIS

An active weather pattern will continue through much of the next week, producing periods of rain and wind, especially along the coast. Following a midweek lull, a more potent system could affect the region late in the week.

DISCUSSION...Now through Saturday

The progressive pattern will continue to support repeated chances for rain through the next week. An upper-level shortwave exiting eastward will see lingering light rain showers this afternoon, before transient ridging supports a drying trend from this evening through early Monday. The next upper-level trough and surface cold front will track inland, bringing rain Monday afternoon before exiting eastward Monday evening. Rainfall totals on Monday are expected to be around 0.25 inches along the I-5 corridor and around 0.5 inches along the coast, Coast Range, and Cascades. Seasonable temperatures in the 50s also continue through this period.

On Tuesday, upper-level ridging will begin amplify inland as another upper shortwave moves into the Pacific Northwest. This will act to limit rain to the coast, Coast Range, and inland areas north of US-20 early, then steadily displace rain chances to the north through Tuesday night. A rather sharp gradient in rainfall totals on Tuesday is expected from south to north, with little to no rain south of US-20, up to 0.25 inches from US-20 to the Columbia River, and 0.25-0.5 inches in southwest Washington, highest on the north shore of Willapa Bay. Heavier rain associated with this atmospheric river is expected over the Olympic Peninsula. Breezy south to southeast winds with gusts as highs as 25-35 mph can be expected along the coast north of Tillamook and over southwest Washington to the west of I-5 through Tuesday night as the front lifts northward.

Upper-level ridging will reach its peak amplitude on Wednesday, supporting dry and unseasonably warm temperatures in the low to mid 60s with light offshore flow. Daily record high temperatures look to remain largely out of reach, however the record values of 64F at Portland (PDX) set in 1989 and 66F at Vancouver (VUO) set in 1904, 1907, and 1930 may be in jeopardy.

There remains good consensus that upper ridging will shift inland while troughing returns to the Pacific Northwest from Friday into next weekend. Long-range ensembles support about a 70% chance for vapor transport to exceed 500 kg/(ms) at the leading edge of this trough on Friday somewhere along the Oregon coast as another potential atmospheric river affects the region. The chances for 2" of rain from Friday morning through Sunday morning are 15-30% along the I-5 corridor and 50-65% along the coast. Repeated rounds of rain and increasingly saturated soils could allow for greater runoff into area rivers, meaning at least isolated flooding cannot be ruled out. -36

AVIATION...Through 06Z Monday

Current observations show widespread VFR conditions. Conditions are expected to slowly CIGs begin to fall towards low-end VFR through 15Z-18Z Monday ahead of the next system. Southwesterly winds along the coast and variable winds inland around 3-6 kt through around 18Z Monday.

The next system arrives Monday morning, returning rain showers to the coast and southern Valley around 16Z Monday, spreading northeastward into the rest of the Valley by 18Z Monday along with Coastal TAF sites. As the front moves in, conditions will trend towards MVFR/IFR along the coast starting around 18Z-20Z Monday, and around 21Z-23Z Monday for inland locations. Guidance suggests a 40-70% chance for MVFR CIGs across the region at any given hour between 18Z Mon-00Z Tue, with the highest chances along the coast. Southerly winds increase tomorrow after 18Z Monday with gusts up to 30 kt along the coast while winds generally remaining under 10 kt inland. However, could see some isolated gusts up to 20 kt for locations within the Central Willamette Valley and neat the mouth of the Columbia River Gorge from 18Z-23Z Monday. For far eastern Portland Metro terminals (KPDX/KTTD), winds trend more east/southeasterly, which could result in some LLWS for KTTD from 20Z-23Z Monday.

KPDX AND APPROACHES...VFR conditions with mid to high clouds. Around 18Z Monday, conditions drop towards low-end VFR/MVFR as the next system approaches. 30-50% chance for MVFR CIGs at any given hour between 21Z Mon-02Z Tue. /42

MARINE

An active weather pattern will continue across the waters through the week. As of early Sunday afternoon, winds remain under 20 kt as we are in between storm systems. However, a steep, long period westerly swell continues to bring seas of 20-26 ft at 14-16 sec through this evening. Seas should gradually fall below 20 ft after 2200 Sunday, and below 17-18 ft after 0100-0400 Monday as the swell comes down. Seas fall as low as 10-13 ft on Monday before the next system arrives. Hazardous Seas Warnings remain in effect for all of the waters including the Columbia River Bar through 0400 Monday.

Winds over the waters begin to ramp up early Monday morning as the next frontal system approaches the waters. High resolution model guidance suggests high confidence (>80% chance) for a return of breezy southerly winds with gale force wind gusts up to 35 kt at any given hour from 0900 to 1600 Saturday. This will result in more wind-driven seas. On Tuesday, another system will bring another round of gale force wind gusts, and an increasing westerly swell will build seas to 13-16 ft at 13-15 seconds. An active pattern continues through the rest of the week with additional rounds of gale force wind gusts. There's a brief break on Thursday before conditions ramp up again at the end of the week. -10

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Hazardous Seas Warning until 4 AM PST Monday for PZZ210- 251>253-271>273.

Gale Warning from 4 AM to 7 PM PST Monday for PZZ210-251> 253-271>273.