Marine Weather and Tide Forecast for St. Helens, OR

SHORT TERM
Now through Thursday night...Expect dry and mostly clear weather through Thursday as high pressure maintains sunny skies and light winds. A ridge aloft is gradually building inland, with upper-level winds beginning to shift more northerly later today. Temperatures will continue a warming trend, with interior valleys reaching the upper 60s to low 70s today, then rising into the low to upper 70s on Thursday. A few spots, especially around the Portland and Vancouver metro, could briefly hit 80 degrees, with probabilities in the 30-60% range.
Overnight lows remain seasonably cool, generally in the 40s across the lowlands. Along the coast, expect some gusty northwesterly winds this afternoon, topping out around 20-25 mph.

Thursday night, a broad upper-level trough begins to approach from the Pacific, shifting the flow aloft more southerly. This pattern favors increasing moisture and elevated instability, particularly over the Cascades. While thunderstorms potential remains limited, some models suggest a small window for elevated convection over the Linn and Lane County Cascades Thursday evening. The NAM indicates modest instability (MUCAPE ~300-400 J/kg), though other guidance is less supportive. As a result, thunderstorm chances have been nudged slightly higher to around 10-15% in that area. Will need to keep an eye on how models trend today. Otherwise, conditions begin to trend cooler and cloudier late Thursday night into Friday as the system moves inland. ~Hall

LONG TERM
Friday through Monday...A more active pattern sets in Friday as a large upper level trough drops into Northern California. This will pull moisture northward into northwest Oregon and southwest Washington, increasing the chance for rain by Friday afternoon. Rainfall totals between Friday morning and early Saturday will vary by location. Current model guidance shows a 10-30% chance of over 0.25 inches along the coast and Willamette Valley, with 30-60% probabilities in the Coast Range and Cascades. Behind the front, cooler air settles in, bringing daytime highs down to the upper 50s to low 60s across much of the area west of the Cascades. Saturday looks to remain unsettled, with intermittent showers persisting as the system exits east into the Intermountain West.

Conditions begin drying out by late Sunday into Monday, as ensemble guidance supports high pressure rebuilding across the region, favoring a return to quieter and drier weather into early next week. ~Hall

AVIATION
The forecast remains on track for the 18z TAF package.
Clear skies/VFR flight conditions should continue across the airspace through 18z Thursday. A few thin high clouds around 25 kft will move in from the south after 12z Thursday. However, there is a 10-30% chance of broken coastal stratus forming around 13-16z Wednesday if northerly winds along the coast take on more of a northwesterly component, which could produce MVFR or high end IFR ceilings. That said, most guidance continues to indicate coastal winds will instead turn to the northeast, which is why skies will most likely stay clear at the coast. Winds remain northerly and generally less than 10 kts for inland areas. Along the coast, north winds increase after 18-20z Wednesday with gusts 20-25 kts possible along the central Oregon coast, including KONP.
Coastal winds will decrease after 02-04z Thursday. -TK/HEC

PDX AND APPROACHES...VFR conditions and clear skies continue through the TAF period. Northwesterly winds become north-northeast after 19-21z Wednesday, generally around 5-10 kts through the period. -TK/HEC

MARINE
Strong high pressure offshore along will maintain northerly winds across all waters through the end of the week. A surface level thermal trough remains over the southern and central Oregon coast through today, which combined with the high pressure offshore will continue increased winds across the waters with gusts up to 25-30 kts at times. A Small Craft Advisory remains in effect for all zones (except the Columbia River Bar)
until 11 PM tonight. Strongest winds are expected in the late afternoon to overnight hours, as well as for the central Oregon coastal waters. The thermal trough will break down tonight, allowing winds to ease Thursday into Friday. Seas are expected to persist around 5 to 8 ft around 10 seconds through the middle of the week. -HEC

PQR WATCHES/WARNINGS/ADVISORIES

OR...None.
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for PZZ251>253-271>273.