textproduct: Portland

SYNOPSIS

A rather active weather pattern continues to steer a series of frontal systems into the Pacific Northwest through the middle of next week with rainy conditions persisting at times. High surf, sneaker waves, and breezy winds impacts continue through this weekend as well. Snow levels fluctuate between 5000-7000ft today and Sunday before falling near 4000 ft in the Cascades Sunday night into Monday and 3000-4000 ft Tuesday into Wednesday - pass snowfall concerns may return.

DISCUSSION...Now through Friday

Early this morning satellite and radar observations depict scattered shower activity streaming across the area while our next weather system cruises east through the Pacific hot on the heels of of our last low pressure disturbance. Until this occurs however, shower activity today likely becomes more terrain locked as the day progresses while the flow gains a southerly component ahead of the approaching front. Then, our next system arrives this evening and is expected to be fairly similar to what we saw yesterday (Friday), though a bit more rain is expected for the coast and terrain in far northern OR and SW WA, and less for the rest of the coast and Coast Range. Also, the heaviest rain is expected in the overnight hours ahead of the frontal passage. Winds will be breezy along the coast once again in the late afternoon through late evening hours, though the last NBM indicates there's only a 10-25% chance for a High Wind event (gusts of 58 mph or higher). Can't rule out a stray gust or two this high at the typical breezy locations (Cape Disappointment, Clatsop Spit, etc), but most locations are expected to see peak wind gusts of 35-45 mph between 8 PM and midnight (right along the frontal boundary).

Once the front passes we'll break into a post-frontal airmass with showers continuing through the day Sunday, mainly over the Cascades, while the associated low pressure system continues spinning in the NE Pacific. Ensembles indicate this low elongates through the eastern Pacific Sunday, pushing east inland Sunday night into Monday. This pattern produces high chances of rain continuing along the coast and Cascades into Monday (80-95+%) with lower chances for the interior lowlands (20-40%). Additionally, colder air filters into the region Sunday into Monday, which will cause snow levels to fall from above 5500-6500 ft Sunday morning to 4000-4500 ft Sunday night. Unfortunately for those hoping for ample snowfall, forecasted precipitation amounts are very low over the Cascades Sunday night into Monday morning with less than 10% chance of even 2 inches of accumulating snow anywhere except for the higher peaks above 6000 ft. However, given unmaintained mountain roads are free of snow and remain open, will need to at least explore Winter Weather product for the Cascades if the precipitation forecast increases even a little bit - something to keep an eye on.

Ensemble members show increasing confidence in a scenario where inland locations could see a brief break in the active weather pattern late Monday night into Tuesday afternoon, though light rain chances continue along the coast. The next weather system is then slated to approach the PacNW coast later Tuesday into Wednesday, though ensemble clusters still indicate quite a bit of uncertainty in the track and therefore potential impacts of this weather system. However, NBM's probability of at least 1 inch of precipitation between 4 AM Tuesday through 4 AM Thursday is only 20-40% along the coast, 10-20% along the terrain, and 5-10% for the interior lowlands, so the trend is for rain impacts to be limited. The airmass will still be on the cooler side when this system hits, and snow levels are forecast to be around 3000-4000 ft Tuesday into Wednesday. Even with the lower precipitation forecast, NBM indicates a 5-15% chance of at least 6 inches of snow at pass level and higher in the 48 hours ending at 4 AM Thursday. This increases to 15-30% chance at pass level and up to 50% chance for higher elevations for at least 3 inches of snow. Highest probabilities near Willamette Pass. Once again, may have to consider Winter Weather Advisories for this weather system even if only a few inches of snow fall. Will be keeping an eye on how the forecast evolves. -99/03

AVIATION...Through 12Z Sunday

Early this morning light to moderate rain showers continue to stream into the region mainly focused over our higher elevation areas. Expect occasional showers to continue impacting each TAF site through 16-19Z Saturday before dissipating and a brief dry period ensues across the lower elevations. Breezy south to southeast winds around 10 kt are expected with occasional gusts to 20-25 kt, except up to 30 kt along the coast.

Ceilings are expected to fluctuate between high-end MVFR and VFR thresholds both inland and at the coast until showers decrease, then back to VFR at this point onward. MVFR thresholds are most likely to occur with passing showers. In general, there is a 20-30% for MVFR ceilings at all TAF sites through 18-19z today. Mostly dry conditions expected for this afternoon but this will be short lived as the next front moves into the area this evening increasing widespread rainfall.

KPDX AND APPROACHES...Expect occasional rain showers to continue through 18-19Z today. Ceilings may fluctuate between high-end MVFR and VFR thresholds with a 30-40% chance of MVFR ceilings centered around 14-19z. After higher confidence in VFR conditions this afternoon, rain increases late in the TAF period as another front moves into the region. Winds remain breezy out of the south today through tonight with gusts around 15-25 knots at times. -99

MARINE

Rather treacherous marine conditions are expected to continue today with observations at Bouy 29/50 showing seas of 23-26ft at 17-20 seconds early this morning - a Hazardous Seas Warning is in effect through 4pm this afternoon. In addition to these elevated seas, another deep low pressure system will quickly spin up in the NE Pacific today, pushing a strong front toward the coastal waters tonight into Sunday morning. Confidence is high for storm force wind gusts of 48-55 kt across our waters accompanying this front, especially beyond 10-20 NM offshore, starting late this afternoon (4pm) and continuing through tonight. Thus, a Storm Warning is in effect for the inner/outer waters including the Columbia River Bar during this time period. Beyond the increase in winds, an additional westerly swell likely nudges seas above the 20 ft mark again Sunday afternoon and night with this swell persisting into Monday.

At least beyond this point seas gradually diminish towards the 10-15 ft range by Tuesday morning. However, another frontal system likely ushers in a period of Gales late Tuesday through Tuesday night followed by a slight uptick in seas on Wednesday (~15ft at 15 seconds). Looking further ahead, there is decent model agreement for seas to drop below 10ft towards the very end of next week as the weather pattern briefly calms. -99/23

BEACH HAZARDS

Dangerous high surf conditions will continue along our beaches today thanks to a very large westerly swell already in place across our waters. Seas are peaking around 25-27 ft at 18-20 seconds early this morning which translates into roughly 30-35ft breakers across the beaches. The High Surf Warning remains in effect for the south Washington coast and northern/central Oregon coast between until noon today. In these conditions, wave will run significantly farther up on area beaches and jetties than what is normally observed. More simply put, the sneaker wave threat will be extreme. Beachgoers should use extreme caution as sneaker waves can suddenly knock people off of their feet and quickly pull them into the frigid ocean which may lead to serious injury or drowning. In addition, large wave runup may dislodge logs on area beaches and result in them rolling up and down area beaches, which have historically killed or seriously injured unsuspecting people, so there will be much more of a threat than just getting wet from a rogue wave. Beach erosion is also expected. Avoid beaches if possible.

The large westerly swell will gradually subside this evening, albeit not by much. The sneaker wave threat remains high during that time despite breaker heights decreasing. Then, another large westerly swell near 20 ft with dominant wave periods of 15-18 seconds arrives Sunday afternoon and lasts into Monday. A High Surf Advisory is in effect from this afternoon once the High Surf Warning ends through Sunday night. High surf conditions, beach erosion, and dangerous sneaker waves continue through the weekend. All in all, please remain extremely vigilant if you insist on visiting our area beaches the next several days - your life may depend on it. -99

PQR WATCHES/WARNINGS/ADVISORIES

OR...High Surf Warning until noon PST today for ORZ101>103. High Surf Advisory from noon today to 4 AM PST Monday for ORZ101>103. WA...High Surf Warning until noon PST today for WAZ201. High Surf Advisory from noon today to 4 AM PST Monday for WAZ201. PZ...Hazardous Seas Warning until 4 PM PST this afternoon for PZZ210-251>253. Storm Warning from 4 PM this afternoon to 4 AM PST Sunday for PZZ210-251>253. Hazardous Seas Warning until 1 PM PST this afternoon for PZZ271>273. Storm Warning from 1 PM this afternoon to 4 AM PST Sunday for PZZ271>273.