Marine Weather and Tide Forecast for Grand Ronde, OR

SYNOPSIS
Dry weather with clear skies through Thursday as high pressure builds over the region. Pattern change returns Thursday night into Friday as an approaching system returns cooler and wetter weather heading into the weekend.

SHORT TERM
Now through Thursday night...High pressure will maintain dry weather with clear skies across northwest Oregon and southwest Washington through Thursday. Zonal flow aloft will turn northerly today into Wednesday as an upper level ridge over the northeast Pacific shifts into the Pacific Northwest.
Expect afternoon highs to gradually warm up the next couple days, with Thursday being the warmest day. Highs are forecast in the upper 60s to low 70s on Wednesday for interior valleys, and mid to upper 70s on Thursday. Can't rule out reaching 80 degrees in the greater Portland/Vancouver Metro Area (NBM guidance suggests a 30-50% probability of exceeding 80 degrees).
Although nights will be clear, frost threat is not expected as lows are forecast in the upper 30s to low 40s west of the high Cascades. Winds throughout the next couple days will generally be light and north-northwesterly, with gusts to 20-25 mph along the coast today and Wednesday afternoon.

Thursday night, the next upper level trough will approach the Pacific Northwest, turning flow aloft more southerly to southeasterly. This kind of pattern typically helps advect more moisture from the south as well as instability as colder air filters in aloft. This is the kind of pattern that could lead to elevated thunderstorms, especially in the Linn and Lane County Cascades. As of now, it's mainly the NAM model showing 700-300 mb MUCAPE values of 100-150 J/kg Thursday evening. The other global models aren't quite showing MUCAPE values of this magnitude yet, so decided to only increase thunder probabilities slightly from NBM in the Linn/Lane County Cascades to around 10-15% Thursday evening. -Alviz


LONG TERM
Friday to Monday...Friday marks a pattern change to cooler and wetter weather. The majority of ensemble members from the GEFS, EPS, and GEPS are in agreement of an upper level trough toward northern California. As this trough moves into California, this will bring showers into northwest Oregon and southwest Washington from the south/southeast as moisture wraps around the low. Probabilities for 24 hour rainfall exceeding 0.25 inch from 5 AM Friday to 5 AM Saturday are around 15-35% along the coast and Willamette Valley, and 40-70% across the Coast Range and Cascades. Highs will also drop into the upper 50s to low 60s for most areas west of the Cascades. Expect a cool weekend with lingering showers on Saturday as the aforementioned low tracks eastward into the Intermountain West.
By Sunday-Monday, precipitation chances decrease as the majority of ensemble members suggest high pressure re-building over the area and returning drier weather. -Alviz

AVIATION
Expect VFR conditions to prevail through the period at most terminal across NW Oregon and SW Washington. Mostly clear skies will be maintained tonight and Wednesday, however, we'll need to watch for a weak push of coastal stratus late overnight into the sunrise hours. An easterly component to the low level flow should keep it mainly offshore, although the latest guidance indicates it may (50-60% chance) shift into or near KAST around ~13-16z resulting in MVFR to high end IFR CIGs should this occur.
Winds stay generally less than 10 kts through the TAF period for most areas. Gusts around 20 kt possible along the coast, especially at KONP Wednesday afternoon.

PDX AND APPROACHES...VFR conditions continue through the TAF period. NW-NNE winds stay less than 10-15 kts tonight into Wednesday morning and afternoon. -Schuldt

MARINE
Strong high pressure offshore along with a surface level thermal trough developing and strengthening over the southern and central Oregon coast will maintain northerly winds across all waters through the middle of the week. As the thermal trough strengthens over the coast, these winds are expected to spread north along the northern Oregon and southern Washington coastal waters, with gusts 25-30 kts possible at times. A Small Craft Advisory remains in effect for zones (except the Columbia River Bar) until 11 PM Wednesday. Strongest winds are expected to ebb and flow diurnally, strongest in the late afternoon to overnight hours, backing off in the morning hours. Winds may drop below Small Craft Advisory criteria during the overnight hours before increasing during the day. Have decided to extend the Advisory for all zones instead of breaking up timeframe given the short lull. Seas are expected to persist around 6 to 8 ft around 10 seconds through the middle of the week. -Batz

PQR WATCHES/WARNINGS/ADVISORIES
OR...None.
WA...None.
PZ...Small Craft Advisory until 11 PM PDT Wednesday for PZZ251>253- 271>273.