textproduct: Portland

SYNOPSIS

Persistent onshore flow will bring near-average temperatures with varying degrees of morning clouds and afternoon sunshine for much of the next week. A series of weak fronts will bring notable chances for light rain and drizzle to portions of the north Oregon coast today and Tuesday.

DISCUSSION...Now through Saturday

Latest satellite water vapor imagery highlights the features which will continue to dictate the weather locally through the coming days: a closed upper low near the Alaska Panhandle and an associated corridor of enhanced baroclinicity and vorticity on its southeast flank, currently extending from southwest to northeast over the Olympic Peninsula and Vancouver Island. A weak frontal boundary, the surface manifestation of the latter feature, continues to bring light rain showers or drizzle to portions of the Washington coast. An upper-level shortwave approaching the region today will push this boundary to the south, bringing light rain or drizzle chances (25-50%) to Pacific County, WA, with lower chances (10-25%) over the adjacent Willapa Hills and north OR coast and Coast Range. Winds rising diurnally in these areas may see southwesterly wind gusts to 15-20 mph this afternoon, but impacts are not anticipated. Otherwise, dry weather is expected across the region with morning low clouds tending to mix out this afternoon, except for more persistent cloud cover along the coast. Seasonable high temperatures in the 60s on the coast and in the low 80s within the Willamette Valley are expected.

As the upper shortwave exits Sunday night into Monday, heights aloft rise somewhat, favoring drier and slightly warmer conditions across the region. By Tuesday, another shortwave will push the weak boundary back toward the coast, yielding light rain chances on the coast and within coastal terrain north of Tillamook, with the highest likelihood again in Pacific County, WA. Reinvigorated marine cloud cover associated with the boundary will also see temperatures cool a few degrees again on Tuesday, before heights again rebuild aloft, favoring a slow warming trend through the remainder of the workweek. Ensemble members continue to highlight another chance for a shortwave and weak surface front to support cooler temperatures and light rain chances along the north OR/souther WA coast late in the week, but uncertainty in the timing and placement of this feature remains high at this lead time. -36

AVIATION...Through 12z Monday

Latest satellite imagery depicts widespread low stratus cover across the region, with terminal observations of MVFR cigs along the coast and largely low-end VFR cigs at inland terminals, except MVFR in the southern Willamette (KEUG) and lower Columbia (KKLS) Valleys. At other inland terminals, low-VFR cigs are most likely (50-60% chance), with 40-50% chances of MVFR cigs until skies trend clearer as low clouds mix out by 16-18z Sun. By this afternoon, largely clear skies are expected inland, while more persistent cloud cover at the coast will see prevailing MVFR or low-end VFR cigs into this afternoon. Low stratus again developing tonight will increase chances for restricted cigs after 03-06z Mon.

Calm to light southerly winds this morning will veer out of the southwest to west and build to 8-12 kt along the coast and 5-10 kt inland. Gusts to 20 kt are most likely along the south WA/north OR coasts including at KAST. Winds ease below 5 kt and back out of the south again this evening and tonight.

KPDX AND APPROACHES...Low-end VFR conditions most likely to continue this morning until skies trend clearer by 16-18z Sun, although there are persistent 40-50% chances cigs lower below 3 kft in the hours around sunrise. Light southerly winds this morning will veer out of the west-northwest and build to 5-10 kt by this afternoon, before easing below 5 kt and backing out of the south again tonight. Additional 25-35% chances for MVFR cigs after 06-08z Mon as low cloud redevelop. -36

MARINE

A weak surface front straddling the coastal waters west of the mouth of the Columbia River will continue to bring chances for light rain today, with southwest winds building to near 15 kt with gusts to 20 kt this afternoon. Chances for gusts of 22-25 kt remain around 50-60% beyond 30 NM off the south WA and far northern OR coasts, however stronger gusts are expected to be intermittent brief, most likely between 8 AM and 2 PM today, and therefore no Small Craft hazards have been issued. South of Cape Falcon and farther from the front, south to southwest winds will remain lighter, 6-12 kt, with rain chances of 15-20% or less. Seas persist at 4-6 ft with a dominant northwesterly swell at 9-10 seconds.

Fairly benign marine conditions with southerly winds and seas of 4-6 ft are expected to continue into Tuesday, when winds will shift to a more seasonable northerly pattern behind another passing frontal boundary. Strengthening northerly flow will see increasing chances (50-75%) for peak diurnal wind gusts to reach 20-25 kt Wednesday and Thursday afternoons, especially within 10 NM of the coast. Seas otherwise continue at 4-6 ft through the remainder of the week. -36

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...None.