textproduct: Portland

SYNOPSIS

Ridging aloft will maintain largely warm and dry conditions through the next week. The only exception will be a weak system arriving Friday into Saturday, which will bring briefly cooler temperatures but only minimal chances for even light rainfall.

DISCUSSION...Now through Tuesday

A narrow upper-level ridge just off the West Coast will broaden through the workweek, driving generally persistent weather conditions across the region. Diurnally-varying marine cloud cover will reach inland overnight into the morning each day, yielding mist or drizzle in areas near the coast, before retreating back to the coast or offshore through the day. There remains uncertainty in the timing of daytime clearing which could greatly modulate high temperatures; the longer clouds persist through the morning, the cooler afternoon highs will be. Even in the reasonable coolest scenario, temperatures should reach near seasonal norms, and will more likely be at least a few degrees above normal each day. Diurnal west winds could also become breezy along the central Columbia River Gorge, with gusts to 25-30 mph in the afternoon and evening through the end of the workweek.

Friday into Friday night, an upper-level shortwave trough will track over the top of the ridge. This feature has trended weaker in recent guidance, with impacts generally limited to enhanced cloud cover and temperatures a few degrees cooler. Rain chances are now minimal across the region, generally 5-15% along the coast and in coastal terrain from Tillamook northward, and in the Cascades north of US-26, peaking Friday afternoon and evening. To the south and at lower elevations inland, chances for even a hundredth of an inch of rain are now 5% or less.

Resurgent upper-level ridging will see the warm and dry weather then continue this weekend into next week, including seasonably warm temperatures in the 60s along the coast and in higher terrain and 70s to around 80 degrees within inland valleys beneath clearing skies on Mother's Day. -36

AVIATION

As of 1730Z Wednesday, ceilings have lowered to MVFR thresholds at all terminals, except IFR at KEUG. Although this stratus deck is not expected to completely clear out today, overcast skies should become scattered to broken by 20-23Z Wednesday with ceilings likely lifting to around 3500-4000 ft for inland TAF sites. Marine stratus is expected to resolidify late this evening into tonight, with MVFR ceilings becoming more widespread again for inland areas. Meanwhile, marine stratus should remain firmly in place through today and tonight along the coast with little to no improvement expected this afternoon. Winds generally remain light and variable around 5 kt or less at all terminals.

KPDX AND APPROACHES...MVFR ceilings remain in place this morning, but should become scattered to broken by approximately 22Z Wednesday while simultaneously lifting to around 3500-4000 ft. Confidence is increasing for another round of high-end MVFR ceilings tonight (40-50% chance), most likely developing sometime between 06-12Z Thursday. -23

MARINE

Strengthening high pressure offshore will see northwest winds intensify and turn more northerly through today, while a broader onshore flow regime will favor continued marine overcast which thickens and lowers overnight before lifting and backing offshore each day through this week. These stronger winds by this afternoon along with a building northwest swell will push seas up to 7-9 ft by tonight, but a dominant swell period of 11-13 seconds should keep seas from becoming steep enough to present a hazard to small craft. Isolated gusts may exceed 20 kt this afternoon into this evening beyond 30 NM.

As northerly flow weakens through Thursday and turns southerly on Friday as a weak system moves onshore, seas will ease back to 4-7 ft. Southerly gusts may briefly approach 20 kt on Friday afternoon before weakening again overnight. Chances for rain showers on Friday have fallen to 5-15%.

High pressure will restrengthen offshore this weekend into early next week, supporting a reintensification of northerly winds. Chances for widespread gusts of 20-30 kt increases daily from Saturday through Tuesday, while seas continue at 4-8 ft. -36

PQR WATCHES/WARNINGS/ADVISORIES

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