Cascade Head to Florence, OR out 10 NM Marine Forecast
|Today...S Wind 10 To 15 Kt With Gusts To 20 Kt, Becoming Se 5 To 10 Kt With Gusts To 15 Kt In The Afternoon. Wind Waves Se 2 Ft At 4 Seconds. W Swell 9 Ft At 13 Seconds. Rain Likely Early In The Morning.|
|Tonight...Se Wind 5 To 10 Kt. Gusts To 15 Kt In The Evening. Wind Waves Se 2 Ft At 4 Seconds. W Swell 8 Ft At 13 Seconds.|
|Sun...Se Wind 5 To 10 Kt, Becoming S 10 To 15 Kt With Gusts To 20 Kt In The Afternoon. Wind Waves S 2 Ft At 4 Seconds. W Swell 7 Ft At 13 Seconds.|
|Sun Night...S Wind 25 To 30 Kt. Gusts To 35 Kt, Becoming 40 Kt After Midnight. Combined Seas 13 Ft With A Dominant Period Of 15 Seconds. Rain Likely.|
|Mon...W Wind 20 To 25 Kt With Gusts To 35 Kt, Becoming Nw 10 To 15 Kt With Gusts To 20 Kt In The Afternoon. Combined Seas 17 Ft With A Dominant Period Of 17 Seconds.|
|Mon Night...N Wind 5 To 10 Kt. Wind Waves N 1 Ft At 4 Seconds. W Swell 14 Ft At 14 Seconds.|
|Tue...Ne Wind 10 To 15 Kt. Wind Waves 3 Ft. Nw Swell 11 Ft.|
|Wed...Se Wind 10 Kt. Wind Waves 1 Ft. W Swell 10 Ft.|
| Area Forecast Discussion|
...UPDATE National Weather Service Portland OR
1002am PST Sat Nov 28 2020
Updated aviation discussion
High pressure will be the dominant weather feature over the upcoming week, but a couple of fronts will bring a good chance for light valley rain and Cascade snow early this morning and then again Sunday night into Monday.
Today through Monday...Water vapor satellite imagery early this morning reveals a shortwave trough sliding eastward across southwest Canada. A broad and weak trailing front is being dragged southward into southwest Washington and northwest Oregon this morning. Given the front is weakening as the upper level support races by to our north and east, rainfall totals should generally be highest across our most northern zones where precipitation is currently falling. However, surface observations indicate rather paltry Quantitative Precipitation Forecast amounts have fallen so far with amounts generally remaining under a tenth of an inch. Models continue to suggest the front will fall apart rather rapidly later this morning and afternoon across our southern and central zones. Cannot rule out some light drizzle/rain continuing during this timeframe in spots, but most locations should dry out entirely during this time.
Farther south GOES-17 Nighttime Microphysics imagery and surface observations early this morning indicate widespread fog and low clouds continuing in the Willamette Valley. Webcams and surface observations indicate fog is most dense in the southern Willamette Valley where a Dense Fog Advisory is in place. Expecting fog to lift with the arrival of the lower and mid levels clouds tied to the front, but confidence is not high that this will occur either. Will monitor visibility trends this morning and update and/or remove the advisory when needed.
Models continue to be in good agreement shortwave ridging will pivot across the region tonight. This should lead to a lowering subsidence inversion and eventually the development of additional fog and low clouds in the valleys of northwest Oregon and southwest Washington tonight. Expect fog and low clouds to once again be slow to clear. However, an increase in east to west pressure gradients across the broader region should keep the coast and areas near the mouth of the Gorge relatively fog and low cloud free Sunday or at least allow those locations to see fog and low clouds dissipate considerably faster than elsewhere.
There continues to be good agreement a subtle shortwave trough currently located over the Aleutian Islands will amplify and move eastward across the Pacific Northwest Sunday night into Monday. A strong low level front coupled with good mid level lift should provide a solid shot of valley rain and mountain snow late Sunday night into Monday morning. Quantitative Precipitation Forecast and snow amounts will be primarily limited by the fast moving nature of the storm system, but low end Winter Weather Advisory criteria may be met above 3000-4000 feet in the Cascades Sunday night into Monday.
Models are also coming around to the idea that low end high wind gusts of 60 mph will be possible along the beaches and headlands ahead of the front late Sunday night. Would like model guidance to paint a similar story for at least another run or two before issuing any headlines given the marginal nature of the event. /Neuman
Monday night through Friday...There continues to be good agreement among the models and their ensembles a large shortwave ridge will build over the Pacific Northwest Monday night into Tuesday. This should result in the area drying out rather quickly. Increasing large scale offshore flow during this time will bring cool and much drier air into the region. This should limit and/or completely eliminate valley fog and air stagnation concerns initially.
However, east winds should become more gap driven during the second half of the week and more confined to the mouth of the Gorge. This should result in dewpoints gradually climbing mid to late week along the lower Columbia Valley and across much of the Willamette Valley away from the Portland metro. This should result in a gradual expansion of valley fog and low clouds late next week. More prolonged air stagnation issues will also likely result across southwest Washington and northwest Oregon away from the Portland and Vancouver metro.
Expect high temperatures to not deviate too much from seasonal averages next week except possibly late in the week when fog and low clouds take hold in areas not affected by the Gorge winds. Overnight low temperatures should end up several degrees below average initially due to the clear skies and infiltration of drier air into the region, but not expecting anything that's unusual when going into a dry offshore flow pattern during this time of the year. /Neuman
Winds across the waters are beginning to dissipate as the front moves over the waters. Wave heigheights will be in the 10 to 13 ft range and drop below 10 ft by Saturday morning.
A stronger front is expected to move onshore Sunday night and Monday. Sustained winds of 30-35 kt are likely early Monday morning ahead of the front. A Gale Warning is possible if models keep trending in this direction. NAEFS & GEFS probabilistic wind speeds greater than 30 kt is only 40-50 percent chance at this time. Seas likely to climb into the mid teens Monday then gradually subside below 10 ft Tuesday. High pressure to return by Tuesday with a summer like pattern with a trough of low pressure near the coastline Wednesday. Winds will turn to an offshore pattern early Wednesday morning through Friday. -BPhillips
.PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory until 10am PST this morning for coastal waters from Cape Shoalwater WA to Florence OR out 60 NM.