textproduct: Portland

SYNOPSIS

Dry weather expected through early this afternoon before light rain begins to push onto the coast by mid-afternoon, spreading inland by this evening. An active weather pattern continues through the remainder of the week and beyond. However, many inland locations will likely see only light accumulations until a stronger system arrives later this weekend. Slightly warmer than average temperatures are expected through Saturday.

DISCUSSION...Now Through Tuesday

Water vapor satellite imagery early Wednesday morning shows the PacNW in-between systems as a transient ridge of high pressure moves over the region. Clearing skies and radiational cooling this morning has allowed for patchy dense fog to develop across the southern Willamette Valley. Have issued a Dense Fog Advisory for the lowlands from Albany to Eugene through 10AM this morning. There is potential for fog to spread northward as the mid-level clouds over northern portions of the area continue to shift east, but confidence is low. If you encounter dense fog Wednesday morning, remember to keep your vehicle headlights on and slow down.

Afternoon temperatures warm into the mid 50s to near 60 degrees as southerly winds increase ahead of our next approaching weather disturbance in the form of an upper level shortwave trough moving across the NE Pacific. The associated frontal system is slated to arrive by mid-afternoon at the coast, spreading rain inland by this evening.Precipitation amounts remain relatively low, with mean QPF values ranging from around 0.01-0.10 inch inland, and closer to 0.10- 0.30 inch at the coast and nearby terrain. A few lingering showers will be possible into Thursday morning, though Thursday will likely see an extended dry period much of the day with temperatures warming again a few degrees above normal.

Uncertainty reigns for Friday as to how far south rain, associated with a weak atmospheric river, will shift. There continues to be large differences between the GEFS, which wants to keep the moisture farther north, and the European ENS, which weakens the upper level ridge allowing for moisture to slide farther south on Friday. The line between wet and dry across our forecast area will likely wobble back and forth near the Portland Metro Area (with areas to the south remaining dry) over the next few days. The spread between the 10th and 90th percentiles of the NBM remain relatively high.

There remains decent confidence in the forecast over the weekend as ensembles are in good agreement depicting broad troughing over the Pacific pushing the upper level ridge farther east over the Rockies. Temperatures are likely to warm well into the 60s across the area on Saturday (near record highs) before a frontal system spreads rain across the Pacific Northwest late Saturday into Sunday. All that being said, 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 before lifting again this weekend. Keep in mind storm drains tend to get easily clogged this time of year. However, beyond day 7 into next week (11/11-11/15), a large number of ensemble systems are beginning to show a growing consensus for a potentially more impactful and active weather pattern. DH/99

AVIATION...Through 12Z Thursday

Light northwest flow aloft becoming westerly later this morning as an upper level ridge of high pressure moves across the region. A few broken mid-level clouds persist over northern portions of the forecast area, but where clearing is occurring dense fog has develops, particularly within the southern Willamette Valley. LIFR conditions likely persist through 18z at KEUG, while reduced VISBY are likely this morning at KHIO, KUAO and KSLE to around 2-4SM. Meanwhile, light easterly winds and the lingering clouds should maintain VFR conditions at KTTD and KPDX. Calm winds along the coast may also allow for some mist to form, though increasing offshore flow may decrease chances for lower flight conditions at KAST and KONP. As of 11z, satellite imagery is showing some MVFR marine stratus developing just west of KAST. A front will approach the area later this afternoon, bringing a brief period of rainfall and lowering CIGs. At this time, VFR conditions are likely to hold on through 04-06z with MVFR CIGs likely developing behind the front. Breezy south winds ahead of the front are likely with gusts up to 20 kt.

KPDX AND APPROACHES...Predominately VFR conditions are expected through 06z Thursday. There is around a 20% chance for surface visibilities below 3SM between 12-17z Wednesday. Light rain is expected to begin this evening sometime between 00-01Z Thu ahead of an incoming front. Chances for ceilings below 3000 ft increase after 06Z Thu to around 50%. Southeast winds around 4-7 kt are expected through this evening. /DH

MARINE

An active pattern arrives as a series of frontal systems will impact the coastal waters beginning today and continuing through the weekend. Southerly winds are expected to increase through this afternoon into early this evening as a frontal system moves across the waters. Small Craft Advisories are in place for winds gusting up to 25-30 kt through 10 PM. Winds shift southwest to westerly behind the front as it pushes onshore tonight. Winds ease, but a westerly swell will begin moving into the waters late tonight, building seas to around 9 to 11 ft at 14 seconds by Thursday morning. Therefore, have extended Small Craft Advisories through Thursday evening.

After a brief lull in winds, southerlies increase again late Thursday into Friday as another frontal system approaches the waters. There is around a 50-70% chance for gale force wind gusts north of Cape Falcon on Friday. Steep and hazardous seas will also be possible later Friday as significant wave heights likely build into at least the mid-teens, though currently just a 10% or less chance for seas reaching 20 ft.

A potentially stronger front is expected to quickly approach the area late Saturday, bringing more widespread chances for Gales (40-80%, highest to the north) across the coastal waters. Another westerly swell will likely build seas into the mid to upper teens, with around a 15-30% chance of wave heights exceeding 20 ft. The active weather pattern likely continues into early next week. /DH

PQR WATCHES/WARNINGS/ADVISORIES

OR...Dense Fog Advisory until 10 AM PST this morning for ORZ116>118.

WA...None. PZ...Small Craft Advisory from 1 PM this afternoon to 10 PM PST this evening for PZZ210.

Small Craft Advisory from 7 AM to 10 PM PST Thursday for PZZ210- 253-273.

Small Craft Advisory from 1 PM this afternoon to 10 PM PST Thursday for PZZ251-252-272.

Small Craft Advisory from 1 PM this afternoon to 7 PM PST this evening for PZZ253-273.

Small Craft Advisory from 10 AM this morning to 10 PM PST Thursday for PZZ271.