Marine Weather and Tide Forecast for Rainier, OR

SHORT TERM
Now through Wednesday Night...Scattered showers continue across northwest Oregon and southwest Washington as the core of a cold upper trough drops south from the Gulf of Alaska. Current radar shows scattered showers over the region and warrants watching as convection is possible this afternoon and evening. Rainfall amounts so far have been rather light, with total precipitation amounts under 0.1 over the past 12 hours. If scattered showers strengthen, heavier bursts of precipitation will be possible.

Cold air continues pushing southward behind the frontal boundary. Snow levels this afternoon are generally around 1500 to 2500 ft but will steadily fall this evening as 850 mb temperatures settle between -5 and -7 degrees C. By late tonight into early Tuesday morning, snow levels are expected to approach 500 to 1000 ft, mostly north of Salem.

For the Cascades, precipitation will remain predominantly snow, and the Winter Weather Advisories remain in effect through at least Tuesday afternoon. Winter Weather Advisories for the North Oregon Cascades and Marion and Linn County Cascades will remain in effect until Wednesday afternoon. Additional accumulations are expected, particularly at pass level and above. Confidence remains high that travel impacts will continue in the higher terrain through Wednesday afternoon. Wednesday afternoon through Thursday afternoon, a Winter Storm Warning will be in effect for the South Washington Cascades, as accumulations over 24 hours are expected to exceed 12 inches.

Lowland snowfall remains complicated as it relies on the timing of cold air and precipitation. Current ensemble guidance supports a 10-20% chance of accumulating snow below 500 ft in the Portland- Vancouver metro area, with probabilities closer to 20-30% in elevated terrain such as the West Hills. Across the Cowlitz County lowlands, probabilities of measurable snow accumulation have decreased to around 20-30%, though chances of reaching 1 inch remain much lower, around 5-10%. At this time, travel impacts appear unlikely for the lowlands. Travel impacts will likely be restricted to higher terrain (above 1000 ft).

The Coast Range remains near the rain-snow line tonight.
Advisory-level snowfall of 2 inches or more remains most favored in the Willapa Hills and the north Oregon Coast Range.
Probabilities for 2 inches vary considerably by model solution, ranging from roughly 10 to 40 percent depending on elevation.
Confidence is highest in the peaks, while valley locations and most travel corridors carry lower probabilities, generally in the 20-40% range (includes Hwy 26 through the Coast Range).

By late Tuesday into Wednesday, an upper trough shifts inland as a high pressure amplifies offshore California, bringing a zonal flow pattern. This will allow warmer air to advance northward in association with a long duration moderate atmospheric river.

Snow levels will rise quickly, reaching 3500 to 4500 ft by Wednesday morning, effectively ending low-elevation snow concerns. The south Washington Cascades may hold onto colder air slightly longer, with snow levels near 2500 ft into early Wednesday before rising. This rise in snow levels will bring the Winter Storm Warning to an end (Winter Storm Warning in effect from 5 PM Tuesday to 5 PM Wednesday).

Wednesday will also bring increasing southerly winds, particularly along the coast and exposed terrain. Wind magnitudes remain somewhat uncertain due to model guidance continuing to exhibit some east wind bias following the prolonged period of offshore flow earlier this month. Ensemble guidance at Cascade Locks continues to show a wide range of gust potential from the south, but southerly wind penetration into that location is climatologically difficult. As such, forecast gusts have been reduced relative to raw model output.
-12

LONG TERM
Thursday through Sunday...The pattern turns wetter on Thursday as the moisture plume becomes better established.
Thursday into Friday currently appears to hold the highest probability for heavier rainfall. Mean 24-hour QPF ending Friday morning ranges from around 2.0 to 2.5 inches in the south Washington Cascades and 1.5 to 1.9 inches along the north Oregon Coast Range and Willapa Hills. Inland totals are lower, generally 1.0 to 1.25 inches near Portland, decreasing to around 0.3 to 0.7 inch Salem southward.

If the atmospheric river axis shifts farther south towards Oregon and less so towards Washington, rainfall totals could increase meaningfully across our forecast area, particularly along the Coast Range and Willapa Hills. This long duration moderate atmospheric river will also come directly out of the west, improving orographic lift efficiency which will result in greater rainfall amounts west of the Coast Range and lesser amounts on the east side of the Coast Range. Ensemble river guidance continues to show flooding probabilities mostly around 5-15%, and even lower for slower-responding rivers. Recent guidance has given one exception, with a 20% chance of minor flooding at the Wilson River near Tillamook on Thursday. Trends will need to be monitored closely over the next 48 hours as hydro concerns may grow as ensemble river guidance hones in on the upcoming precipitation.

Heading into the weekend, uncertainty increases substantially.
Ensemble cluster analysis shows roughly equal support for wetter versus drier solutions and warmer versus cooler outcomes. The spread in 10th to 90th percentile temperatures highlights this uncertainty, with potential swings exceeding 10 degrees in many locations on Saturday and around 18 degrees on Sunday. The strength and placement of Pacific high pressure and the position of the jet stream relative to the region will influence the outcome.
-12

AVIATION
Mainly VFR conditions continue over the area with scattered clouds below 5 kft and thicker broken to overcast clouds between 5-8 kft. Scattered showers continue over the area with the highest coverage along the coast and north of KSLE which may briefly restrict VIS/CIG to MVFR or lower. The showery pattern continues into tonight with a brief decrease late tonight before the next round of showers moves into the area Tuesday morning. A low, 10-20% chance of thunderstorms remains in the forecast through late this evening around 06z but given the low chance and low areal coverage, anything that develops is unlikely to impact a terminal directly.

Tonight after 06z Tue, there are low chances for low-elevation snow from KKLS northward along the Cowlitz Valley, although light snowfall rates and minimal surface accumulations will limit surface impacts. Chances for MVFR or lower CIGs also increase during this time with a 20-50% chance throughout the Willamette Valley during any given hour after 06z. West winds at 5-10 kt continue through this evening and into tonight, turning out of the south to southwest at 5 kt or less after 06-12z Tue, then increasing again after 18z to around 10 kt from the southwest with gusts 15-20 kt.

KPDX AND APPROACHES...VFR flying conditions likely through 06z with increasing chances for MVFR CIG/VIS to 30-60% any given hour.
Scattered showers continue through the evening, decreasing in coverage tonight before increasing again Tuesday morning. There is a 10-15% chance of an isolated thunderstorm through 06z, but terminal impacts are very unlikely. West winds of 5-10 kt turn out of the south to southwest at 5 kt or less after 06z Tue.
-19/36

MARINE
Scattered post-frontal rain showers continue this afternoon while an isolated thundershower also cannot be ruled out, particularly north of Cape Falcon through this evening. Seas of 8-11 ft per buoy observations early this afternoon are expected to slowly increase to 10-12 ft, then maintaining those levels through Tuesday night, while west to northwest winds around 15 kt with gusts to 20-25 kt will ease tonight, then turn out of the southwest and build to around 20 kt through over the same period.
Small Craft Advisories will therefore expand to cover all the coastal waters by 8 PM PDT this evening, and further to include the Columbia River Bar by 8 AM PDT Tuesday morning.

A stronger frontal system will traverse the waters Wednesday and Wednesday night. The locally tightened surface pressure gradient will see winds and seas increase through the day. There is high confidence (80% or higher chance) that at least isolated gale- force gusts will occur over the waters, however more persistent or widespread gale-force gusts remain less likely (25% or less chance in any given hour). The enhancement of southerly winds within 10 NM of the coast as southwest winds are blocked and deflected by coastal terrain render nearshore areas more likely to see gales, but locations where coastal enhancement will occur remains sensitive to the position of the frontal system and its parent area of low pressure. As such, a Gale Watch has been issued for areas north of Cape Foulweather from 10 AM PDT Wednesday through 7 AM PDT Thursday, during which time the strongest wind gusts are expected. Meanwhile, seas may build to 15 ft or higher, although again, the location of the highest seas is dependent upon the frontal position. Additional Hazardous Seas Watches may be needed if forecast swell height increases and the coverage of higher seas expands beyond the area of high winds, and additional Small Craft Advisories may be issued for areas likely to remain below Gale or Hazardous Seas conditions.

The pattern remains active late this week and into this weekend, but confidence in the occurrence of hazardous conditions is low at this time. -36

PQR WATCHES/WARNINGS/ADVISORIES

OR...Winter Weather Advisory until 5 PM PDT Tuesday for ORZ106.

Winter Weather Advisory until 5 PM PDT Wednesday for ORZ126-127.

WA...Winter Weather Advisory until 5 PM PDT Tuesday for WAZ211.

Winter Storm Warning from 5 PM Tuesday to 5 PM PDT Wednesday for WAZ211.

PZ...Small Craft Advisory from 8 AM Tuesday to 8 AM PDT Wednesday for PZZ210.

Small Craft Advisory from 8 PM this evening to 8 AM PDT Wednesday for PZZ251>253-273.

Gale Watch from Wednesday morning through late Wednesday night for PZZ251-252-271-272.

Small Craft Advisory until 8 AM PDT Wednesday for PZZ271-272.