Marine Weather and Tide Forecast for Scappoose, OR

DISCUSSION
Now through Thursday...Another day of dry and sunny weather today as the short wave ridge peaks over the region. Temps expected to peak in the mid to upper 70s inland and in the low 60s along the coast. Winds inland remain light and offshore, helping support dry, downslope winds on the west side of the Cascade crest. The offshore pressure gradient has weakened along the coast where onshore flow has returned and helped keep temps lower and dew points higher, around 45-50 degrees. Min RH values are expected to drop into the 20-30% range (40-50% along the coast) as the dry airmass remains in place and temps rise well above normal. Not expecting any fire weather concerns at this time as winds remain below 10 kt and gusts up 15 kt.

The pattern shifts as we move into the weekend, beginning late tonight. A series of short wave disturbances are expected to move across the region shifting the short wave ridge east of the Cascades. Significant precipitation is not expected through the weekend but light showers are possible, mainly along the north OR/south WA coasts and north of the Portland metro. The first trough could bring, at most, a few hundredths but most locations should see just a sprinkle. This is followed by another weak trough pushing in on Sunday, bringing around 0.05-0.15" of rain accumulation between 5am Saturday to 5am Sunday. Afterwards, a series of weak disturbances pass through the area over much of the following workweek, though rain accumulation is expected to be fairly minimal during this time. Daytime high temperatures in the begin in the lower 60s Monday but gradually increase through the middle of the week toward the low 70s. WPC Cluster guidance shows around a 60% chance of a slightly more impactful trough moving in next Thursday.
There remains plenty of uncertainty in exact intensity and impacts with this late week system. -Batz/JLiu

AVIATION
An upper ridge of high pressure remains over the region today with mostly clear skies and VFR conditions persisting through at least 00z. Flow turns back onshore this evening as a weak front approaches, likely pushing marine stratus onto the coast by 02-03z Saturday. Will also see increasing mid to high level clouds inland. CIGs along the coast will likely fall to MVFR, along with a 70-80% chance of IFR cigs between 04-12z Saturday. Northwest winds along the coast are expected to increase this afternoon with gusts to around 20 kt.

PDX AND APPROACHES...VFR through the TAF period. Increasing clouds later tonight with CIGs lowering to around 4000-6000 ft after 12z Saturday. Northwest winds expected around 4-8 kt, strongest in the afternoon. /DH

MARINE
Strong high pressure offshore will maintain northerly winds across the coastal waters today and through the weekend.
Winds are expected to increase later this afternoon with gusts up to 20-25 kt through tonight. A weak surface front will drop across the waters with northerly winds peaking Saturday morning, with gusts up to 25-30 kt. Additionally, seas around 5 to 7 ft at 13 seconds will build to 8 to 10 ft at 10 seconds tonight, continuing into Saturday. Will maintain the Small Craft Advisory through Saturday evening.

Another weak front moves across the waters on Sunday. By Monday, the thermal trough strengthens over the southern Oregon coast, increasing the northerly pressure gradients again for early next week. Seas are expected to persist around 6 to 7 ft. /DH

PQR WATCHES/WARNINGS/ADVISORIES

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