Marine Weather and Tide Forecast for Portland, OR

SHORT TERM
Now through Thursday night...Radar imagery as of early Wednesday morning depicts scattered showers off the south Washington and north Oregon coasts as a weak cold front approaches the area. Rain is expected to be very light today as this front progresses inland. Amounts are forecast around 0.05-0.10" along the coast, and a trace to 0.05" for the Portland Metro and southwest Washington lowlands. Most other locations remain predominately dry this morning. By this afternoon, dry weather will prevail across all of northwest Oregon and southwest Washington as the front dies off. Cloud cover will also begin to break out, leading to increasing sunshine. As a result, high temperatures are forecast to peak in the low 70s today with upper 50s to low 60s along the coast.
Westerly to southwesterly winds are generally forecast under 10 mph today for most places, however, expect breezier conditions through the Columbia River Gorge. As pressure gradients tighten this afternoon, westerly winds could gust to 25-35 mph through the Gorge and Upper Hood River Valley.

Surface high pressure returns on Thursday, briefly returning northerly to northwesterly winds across the area with breezy westerly winds through the Gorge. Overall dry on Thursday, however, cloud cover will gradually increase ahead of the next system. Thursday's high temperatures are forecast similar to today - low 70s inland and upper 50s to low 60s along the coast. Thursday night, the next cold front approaches the Pacific Northwest, leading to a pattern change towards cooler and wetter weather as we head into the weekend. -Alviz

LONG TERM
Friday through Tuesday...There is high confidence for much cooler and wetter weather across northwest Oregon and southwest Washington at the end of the week. There continues to be excellent agreement among ensemble members for an upper level trough dipping down into the Pacific Northwest from the northeast Pacific. Temperatures will drop on Friday and Saturday, with highs forecast to peak in the upper 50s to low 60s across interior lowland valleys.

The initial surface cold front associated with the upper level trough will arrive on Friday, returning widespread showers. A secondary shortwave will then arrive on Saturday as the upper level low moves directly overhead, continuing the wet weather.
Will note that there is a 15-20% chance for thunderstorms Friday afternoon. Cold air aloft from the trough will increase atmospheric instability and steepen lapse rates. Combined with abundant moisture and lift, this will be favorable for the development of thunderstorms or heavy showers. Any passing thunderstorms could produce lightning, downpours, or gusty outflow winds. When thunder roars, go indoors!

The bulk of the precipitation is forecast from early Friday morning to early Sunday morning. A soaking rain is likely, as 48-hour probabilities for 0.50" of rain or more from 5 AM Friday to 5 AM Sunday is around 50-70% for interior lowland valleys and 70-90% along the coast and high terrain. For 1" or more of rain in 48 hours during this same time period, probabilities are around 10-20% for interior lowland valleys and 30-50% along the coast and high terrain. The current rainfall forecast calls for 0.50-0.75" across the Willamette Valley and southwest Washington lowlands, 0.75-1.25" along the coast and Coast Range, and 0.75-2" across the Cascades. Given the showery nature of precipitation this weekend, some locations will significantly overperform for total rain amounts while other locations underperform. That said, forecast rain amounts are still fairly substantial for all locations for this time of year.

Dry weather returns on Sunday as high pressure re-builds. High pressure will continue heading into early next week, leading to sunnier and warmer conditions. Temperatures will rebound, with NBM guidance suggesting a 60-80% chance that temperatures exceed 80 degrees across the Willamette Valley by Monday and Tuesday. -Alviz

AVIATION
Observations from around the area show a mix of MVFR and VFR cigs as of 18z Wed, with light rain showers diminishing on radar behind a weak front departing into the Cascades. Conditions will continue to improve towards VFR through 20z as clouds scatter out behind the front. Models depict a 60-80% chance for MVFR conditions to redevelop along the northern coast including KAST around 12z Thu, with closer to a 30-50% chance along the central OR Coast including KONP. Expect inland terminals to remain VFR through the rest of the period once clouds scatter out this morning. Winds shifting out of the northwest and increasing to 8-12 kt 22-01z today. then diminishing below 5 kt after 06z Thu.

*KTTD ASOS is currently INOP except for altimeter and will be AMD NOT SKED.

PDX AND APPROACHES...VFR conditions expected through the period.
Light rain showers tapering off behind a departing front with cigs increasing above FL040 by 20z. Winds around 8 kt shifting from S-SW to W by 21z, then increasing out of the NW at 10 kt after 00z Thu. Winds diminishing near or below 5 kt after 08z Thu. /CB

MARINE
Although a weak front continues moving through the waters early this morning, relatively quiet conditions continue across the coastal waters as buoy observations show 5-15 kt winds and 3-5 ft seas. Southerly will shift back to the northwest today in the wake of the front, remaining 5-15 kt through early Friday as surface high pressure builds back over the waters. Seas will build to around 5-6 ft on Thursday, with a modest westerly swell as the primary contributor. The arrival of an unseasonably deep trough of low pressure will bring more unsettled conditions from Friday into the weekend, with winds increasing closer to small craft criteria and seas building to 7-8 feet by Saturday.
-CB/HEC

PQR WATCHES/WARNINGS/ADVISORIES

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