Marine Weather and Tide Forecast for Dunes City, OR

SYNOPSIS
Dry weather this weekend as high pressure builds over the region. Offshore flow will also increase, with breezy easterly winds through the Columbia River Gorge and eastern Portland/Vancouver Metro. A weak shortwave trough will bring a chance for light rain across the forecast area starting late Sunday night/early Monday morning. Light precipitation will continue to spread across the CWA through Monday. Relatively dry conditions for Tuesday, with widespread precipitation and with cooler temperatures starting Wednesday and expected to persist through the end of next week.

DISCUSSION
Today through Saturday...An upper level ridge will continue to build over the Pacific Northwest through the weekend and result in drier conditions across the CWA As the upper level ridge builds over the area, a thermally induced surface trough also develops will result in easterly winds through the Columbia River Gorge and eastern Portland/Vancouver Metro Area. Latest guidance from the GFS, NAM and SREF have the KPDX to DLS pressure gradient peaking around -6 to -8 mb Saturday night into early Sunday morning. Given that easterly winds have been slightly stronger and earlier than initial guidance had suggested, the peak still looks to be overnight, but might last longer and be slightly stronger. At this time, expect wind gusts up to 45 mph for the far eastern Portland/Vancouver Metro area (Troutdale/Camas), and up to 60 mph for exposed ridgetops (Crown Point and Three Corner Rock).
Sunday is shaping up to be slightly warmer than today as the upper level ridge amplifies and shifts eastward over the Great Basin.

Sunday night into Monday, the upper ridge begins to flatten as a shortwave trough pushes into British Columbia and NW Washington.
Guidance is showing that the front associated with this upper level shortwave will either track northward, be relatively weak or both. The result is a moderate to high PoP/low QPF scenario.
Currently, the highest chances for rain are along the coast and southwest Washington (50-80%), while chances for rain are lower (20-40%) across interior northwest Oregon. Precipitation will likely arrive at the coast late Sunday evening/Sunday night and slowly push inland through Monday morning. Total precipitation with this shortwave for the coast and SW Washington range from 0.01-0.10 inches and for NW Oregon range from a Trace to 0.05 inches over a 24-36 hour period.

Tuesday, another shortwave upper level ridge builds over the Pacific Northwest and this will bring a brief return of dry weather. However, by Wednesday, this ridge quickly gets pushed eastward as a more robust low in the NE Pacific takes aim at the Pac NW. This more robust system will bring rain and cooler air back into the forecast. Current guidance has precipitation starting Wednesday morning. Precipitation will remain in the forecast through at least the end of the week. Thursday will also introduce cooler air into the forecast. 850 mb temperatures fall towards -1 to -3 C, which would also bring snow into the forecast for higher elevations within the Cascades. It is still well into the future for accurate snow accumulations for the Cascades, but we will continue to monitor and update the forecast. /42

AVIATION
High pressure inland continues to support offshore flow and largely VFR conditions across the region. Gusts of 20-30 kt reach west of the Columbia Gorge to KPDX/KTTD and through other east-west oriented terrain gaps, but will trend downward late Saturday night through Sunday morning as the pressure gradient begins to weaken. These east winds will inhibit any fog formation at both Portland-area terminals as well as along the coast. Cigs begin to trend downward late in the period as a weak frontal system approaches the coast, with a 30% light rain showers reach KAST by 03-06z Mon.

Along the Willamette Valley, as well as other sheltered valleys in the Coast Range and Cascades, light north to northeasterly winds will support another night of valley fog/mist or low stratus.
Confidence in fog development is the highest east of I-5 in the southern and central Willamette Valley, most notably including KEUG where there is a 50-70% chance in IFR vis/cigs within fog as soon as 08-10z Sun. Chances for IFR conditions are lower to the north including at KSLE/KUAO/KHIO, some 20-40%, with periods of MVFR vis in mist more likely. If northerly winds remain higher, a low stratus deck may be favored instead of surface-based fog. Any restricted vis should clear by 17-20z Sun.

KPDX AND APPROACHES...VFR conditions expected through the TAF period. East winds of 15 kt with gusts to 25 kt will continue tonight, before easing to around 10 kt after 12-15z Sun. -36

MARINE
High pressure building inland will drive offshore (easterly) winds around 10-15 kt today. Some gusts up to 20-25 kts are possible in stronger gap-flow winds due to offshore flow, though they are not widespread enough for a Small Craft Advisory. Winds turn south to southeast on Sunday as a weak front approaches the waters, decreasing as gap-flow winds end.
Seas of 6-9 ft at 10-12 seconds this evening will generally remain this way through Sunday. However, another strong ebb Sunday evening will yield seas of 9-10 ft in the Columbia River Bar, where a Small Craft Advisory is in effect from 4-10 PM.

Wind direction varies through the first half of next week, but wind speeds look to remain at 5-10 kt through Wednesday morning.
There is also high confidence (greater than 95% chance) that seas remain below 10 ft through midweek as well. An area of low pressure strengthening well offshore will see increasing southerly winds and a building southerly swell, increasing the chances for another period of conditions hazardous to small craft late Wednesday into Thursday. At this point, gale-force winds are not favored during this period, with 30-50% chances of occurrence beyond 20-30NM.

PQR WATCHES/WARNINGS/ADVISORIES

OR...None.

WA...None.

PZ...Small Craft Advisory from 4 PM to 10 PM PST Sunday for PZZ210.