textproduct: Portland

SYNOPSIS

Another coastal weather system will brush the area tonight into Thursday morning bringing light rain, with dry conditions otherwise expected through the workweek. The pattern then shifts wetter and colder this weekend into early next week.

LONG TERM...Saturday through Tuesday

This weekend into early next week, the ridge axis will slowly slide eastward toward the Rockies, allowing the storm track to dip south into the Pacific Northwest and resulting in steadily increasing chances for precipitation across the region. Global ensembles remain in fairly good agreement given the lead time that an upper-level shortwave trough will track toward western Washington or northwestern Oregon, although the timing of this feature remains more uncertain, ranging anywhere from Sunday night through Tuesday. Additionally, the ensemble mean mid-level temperatures overhead have continued to trend warmer through the period in question, supporting a scenario where even if plentiful moisture and synoptic lift are present, the column may simply be too warm to see impactful snow at pass-level. As such, the chances for 6 inches or more of snow have fallen substantially to 5-10% at the Cascade passes from Sunday through Tuesday. On the heels of this shortwave, however, another shot of colder temperatures could reach the region toward the middle of next week. -36

AVIATION

High pressure remains in place overhead, supporting widespread inland fog early this morning. Light and variable winds will become easterly at Portland-area terminals by 15-18z Wed, and this drier east flow will aid in clearing low clouds. KTTD is unlikely to see restricted vis/cigs as long as light east flow remains in place, but there remains a 10-20% chance that fog encroaches from the west if winds slacken. Elsewhere in the Willamette Valley, fog and low clouds will be slow to scour out as low-level flow is likely to remain very light through much of the morning, meaning terminals may not clear until 18-21z Wed.

Along the coast, east flow at KONP will likely maintain VFR conditions, however a few low cloud may yet sneak through coast range gaps, albeit not with enough coverage to restrict flight categories. To the north at KAST, favored east-southeast flow will see intermittent vis restrictions within fog, before conditions improve by 16-18z Wed as winds strengthen.

Late in the period, by 02-03z Thu at the coast 04-06z Thu inland, an occluded front will move onshore. This will see winds build out of the south for most of the region, and out of the southeast at Portland-area terminals. On the coast, southerly gusts of 15-25 kt are expected. The frontal passage will yield light rain with 60-70% chances of MVFR cigs at all terminals this evening.

KPDX AND APPROACHES...Intermittent IFR/LIFR fog has developed and are expected to continue until drier east winds reach the terminal, most likely by 15-16z Wed but with a 10-15% chance of a low stratus deck lingering as late as 18-19z Wed if winds are slow to strengthen. VFR conditions will then prevail through the afternoon, until a frontal passage will see light rain and an 80% chance of MVFR cigs after 06z Thu. -36

MARINE

Fairly tranquil conditions in place early this morning with regional buoys reporting 5 ft seas at light east winds of 5-10 kt, although locally stronger winds may exist west of gaps in coastal terrain. Winds will turn out of the south and build to around 20 kt gusting to around 25 kt through this afternoon ahead of an approaching frontal boundary while seas build to 6-8 ft with a dominant west-northwest swell. Small Craft Advisories will go into effect at 1 PM across the outer waters beyond 10 NM, and at 7 PM across the inner waters due to these gusty south winds.

While south to southeast winds will ease to around 10 kt through tonight, a rapidly building long-period westerly swell will see seas climb to 16-19 ft by Thursday afternoon and evening. As such, Hazardous Seas Warnings have been hoisted across the coastal waters from 10 AM Thursday through 4 AM Friday, spanning the time when seas are forecast to remain above 15 ft. At the same time, steep seas of 10-14 ft will make for a hazardous crossing of the Columbia River Bar, especially during a strong ebb tide Thursday afternoon, coinciding with some of the highest seas. A Small Craft Advisory is therefore also in effect for the bar from midday Thursday through Thursday night.

The long-period westerly swell will ease on Friday, but remain at 10-12 ft into early next week, allowing elevated seas to persist through at least Monday. Southwesterly winds around 10 kt will also continue through Sunday before turning out of the north at 10-15 kt on Monday. -36

BEACH HAZARDS

An energetic westerly swell is expected along the northwestern Oregon and southwestern Washington coasts for a long duration from Thursday through next Monday. Initially, the swell will reach 15-18 ft at 15 seconds through much of Thursday, before weakening slightly to 10-12 ft at 12-15 seconds from early Friday afternoon through the the weekend. Even when this swell is slightly lower amplitude, its long-period nature will yield a high risk for sneaker waves along area beaches. These energetic waves can run significantly farther up a beach than normal, including over rocks and jetties, creating potentially life-threatening conditions in the surf zone when beachgoers can be unexpectedly knocked off their feet and pulled out into cold ocean waters.

A Beach Hazards Statement has therefore been issued from 5 AM Thursday through 5 AM Monday. Caution should be used when in or near the water, and beachgoers with children should be especially watchful. Never turn your back on the ocean, and be sure to keep an eye on the waves. Those participating in razor clam digs should additionally exercise caution. -36

PQR WATCHES/WARNINGS/ADVISORIES

OR...None.

WA...None.

PZ...Small Craft Advisory from 10 AM Thursday to 4 AM PST Friday for PZZ210.

Small Craft Advisory from 7 PM this evening to 10 AM PST Thursday for PZZ251>253.

Hazardous Seas Warning from 10 AM Thursday to 4 AM PST Friday for PZZ251>253-271>273.

Small Craft Advisory from 1 PM this afternoon to 10 AM PST Thursday for PZZ271>273.