textproduct: Portland

SYNOPSIS

Mostly dry conditions likely persist through Tuesday as a weak frontal boundary grazes the coast to the west. Then, after ample inland fog/low clouds to start Wednesday, an active and wetter weather pattern returns late Wednesday through the end of the week and beyond. However, weather related impacts over the next 5-7 days remain fairly limited, staying within climatological norms for early November.

DISCUSSION...Now Through Sunday

An upper-level ridge of high pressure continues to progress eastward this afternoon with weak offshore flow helping to scour out a much wider swath of low clouds/fog compared to this time yesterday. Still, the inversion and low clouds have remained persistent from roughly Salem/Albany southward. It may take until the late afternoon for the south Willamette Valley to see improvement. Otherwise, both satellite and radar observations are also depicting a weak system brushing the coastline which is responsible for some of our added high clouds and filtered sunshine for the locations devoid of low stratus/fog. There is a 10-15% light precipitation brushes the north Oregon coast towards the Long Beach Peninsula/Willapa Hills this evening, but more likely the dry conditions hold.

Come Tuesday the low pressure system off the northern California coast moves east, remaining south of the forecast area while dragging a broader weak large scale trough feature overhead by the late afternoon and evening. That said, models are in good agreement in dry weather persisting. Before the axis of this feature is able to move inland, the resulting offshore surface pressure gradient likely peaks Tuesday morning with continued breezy east winds through the Columbia River Gorge and Cascade gaps before weakening late in the day - the NBM gives a 40-55% chance for max gusts to exceed 40 mph in the western Gorge. At least the weak troughing moving overhead, cooling temperatures in the mid-levels Tuesday afternoon should weaken the temperature inversion and help any lingering low cloud/fog clear out by the afternoon.

On Wednesday, a shortwave trough moving across the NE Pacific quickly pushes a frontal system toward the coast later in the day. Conditions appear rather conducive to fog and low stratus formation again to start the day, followed by increasing precipitation chances across the area in the afternoon through Wed night. Most ensembles indicate this system will be weakening with just light amounts of rainfall, most likely 0.1-0.30" coast range, <0.10" inland valleys. Cluster analysis of 500 mb heights are in relatively good agreement heading into the latter part of the week with zonal to southwest flow aloft allowing for a somewhat active pattern over the NE Pacific to approach the coast. By the weekend, ensembles are in decent agreement depicting a broader ridge axis building east of the Cascades. There is still quite a bit of uncertainty in regards to exact rainfall coverage and amounts, but there is continued potential for multiple rounds of systems moving across the area into next weekend. At this point, no significant precipitation impacts are expected with any of these weather systems over the next 5 to 7 days, and snow levels hold around 5000-6000ft. However, beyond day 7 into next week (11/10-11/14), almost all ensemble systems like the EPS, GEFS, etc. are beginning to show a growing consensus for a much more impactful and active weather pattern - a period of time we'll have to watch closely. -99/DH

AVIATION...Through 00Z Tuesday

Satellite imagery and terminal observations as of early Monday afternoon depicts predominately VFR conditions with increasing high clouds across northwest Oregon and southwest Washington. Tonight, expect these trends to continue for most terminals. An exception would be KHIO and KEUG, where there is a 15-30% chance for IFR/LIFR CIGs/VIS at any given hour between 12-18z Tue. Light northerly winds under 5 kt expected across the central and southern Valley today. Elsewhere, offshore pressure gradients will support increasing easterly winds along the coast and eastern Portland Metro Area, with gusts up to 22-24 kt at KTTD.

KPDX AND APPROACHES...Predominately VFR conditions through the TAF period with high clouds. Easterly winds around 3-5 kt. -10

MARINE

Light east to southeast winds continue through this evening as a low pressure system remains well offshore. A long period west-northwest swell will maintain seas around 8 to 10 feet at 14-17 seconds through Tuesday. Will keep the Small Craft Advisory for the outer coastal waters up for now, however, seas are marginally hitting small craft conditions, so this Advisory could potentially be dropped early if seas end up falling. This long period swell will also result in a moderate threat for sneaker waves at the coast today through Wednesday. Caution should be used at beaches when in or near the water.

Winds become light and variable on Tuesday, then turn more southerly by Wednesday ahead of an approaching frontal system. This system is expected to be relatively weak, with around a 50-60% chance for wind gusts up to 25 kt north of Cape Falcon. By the end of the week, model guidance hints at a stronger system entering the waters, resulting in a 50-70% chance for maximum wind gusts exceeding 34 kt north of Cape Falcon on Friday. In addition, another long period westerly swell will likely build seas into the mid-teens with a 10-20% chance for significant wave heights exceeding 20 ft. -10/DH

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 7 AM PST Tuesday for PZZ271>273.