textproduct: Portland

SYNOPSIS

Today through Monday, a shortwave ridge of high pressure will bring a brief period of dry and warm conditions with mostly sunny skies. Tuesday through the end of the week, will see a significant pattern change with cooler temperatures, widespread rain chances, and a 5-15% chance for thunderstorms. Wednesday and Thursday are expected to be the wettest days. Towards the end of the week, warmer and drier conditions are expected to return, but there is a lot of uncertainty in the forecast.

LONG TERM...Wednesday through Saturday

Wednesday into early Thursday is shaping up to be more significant, as the stronger of the two systems move into the Pac NW. The associated front with this system swings through on Wednesday, bringing more widespread rain, cooler temperatures, and breezier southerly winds. Chances for exceeding 1 inch of rain in 48 hours between 5 AM Wednesday to 5 AM Friday are around 75-90% across the CWA, with the highest chances along the coast, Coast Range, and Cascades. Chances for exceeding 2 inches during this same timeframe are around 25-40% for these higher terrain features, and 10-20% along the I-5 corridor.

Thursday afternoon to Friday, the upper-level trough moves directly overhead and we transition into a post-frontal environment with lingering showers. Given that there will be cooler air aloft, this will favor increasing atmospheric instability and thus chances for thunderstorms. There is around a 15-20% chance for thunderstorms on Thursday following the initial frontal passage. Any passing thunderstorms may produce lightning, heavy rain, erratic winds, and small hail. Overall, while the upcoming rain will not quite yet be a "fire season ender," it will definitely slow down fire season and help put a damper on ongoing wildfires. /42-10

AVIATION...Through 12Z Monday

Generally VFR conditions across the airspace. However, satellite imagery is showing some patchy stratus developing at various locations across the airspace. Primarily, the marine stratus is developing near PDX, KTTD and in- between KSLE and KEUG. With that in mind, there is a 20-40% chance for MVFR conditions to at these locations through at least 16Z Sunday. Any lowered flight conditions that do develop, should return back to VFR between 16Z-18Z Sunday, which should persist through the remainder of the TAF period.

Winds generally north to northeast less than 6 kts through 16Z Sunday, becoming more northerly and increasing to 6-10 kts after 18Z-21Z Sunday. Also, expect gusts approaching 22 kt around KEUG and KONP starting around 19Z Sunday through around 03Z Monday.

KPDX AND APPROACHES...VFR conditions prevail with a 20-40% chance of MVFR conditions developing through 16Z Sunday. Conditions expected to improve to VFR between 16Z-18Z Sunday. Winds generally north to northwest 3-5 kts, increasing to around 7-10 kts after 22Z Sunday. /42

MARINE

A shortwave upper-level ridge will build over the waters through Tuesday. This maintain north/northwest winds that will slowly strengthen as the ridge builds, reaching diurnal peaks around 10-15 kt Sunday and Monday afternoons. By Tuesday, a more robust upper-level trough digging over the northeast Pacific will result in a southerly wind shift across all waters by Tuesday morning. Largely wind-driven seas through this period will persist around 4-6 ft.

As the aforementioned trough and associated fronts approach the coast Tuesday into Wednesday, will bring increasing southerly winds with gusts up to 35 kt possible. If the forecast trends continue, will likely be issuing a Gale Watch in the near future. Seas will similarly build towards 10-12 ft as winds increase along with a fresh swell. Towards the latter part of the upcoming week, expect winds and seas to ease. /42

PQR WATCHES/WARNINGS/ADVISORIES

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