textproduct: Portland

SYNOPSIS

After a storm system clips the area today, expect drier weather Wednesday and Thursday before another storm system brings widespread rain and breezy conditions to the area Friday into the weekend. Sneaker waves will be a threat through the week with another round of high surf conditions appearing increasingly likely Saturday.

MORNING UPDATE

A Flood Advisory has been issued for the Portland/Vancouver Metro Area through 2 PM this afternoon due to heavy rain which is leading to minor flooding in low-lying and poor drainage areas. Ponding of water on roads is occurring. Around 0.40- 0.80" of rain has fallen in the last 12 hours, and 0.25-0.40" in the last hour. Be aware of your surroundings and do not drive on flooded roads. Rain is expected to decrease this afternoon. -10

DISCUSSION...Now through Monday

Water vapor satellite imagery early Tuesday morning depicts a large swatch of moisture approaching the northern PacNW. This is the next atmospheric river slated to impact the region as the associated frontal system will slowly approach the WA and far northern OR coast today through Wednesday. Some light scattered showers are possible early this morning across all of NW OR and SW WA before upper level ridging begins building east of the Cascades, limiting the main bulk of the precipitation to locations north of US-20 this morning then steadily moving north into Washington through the afternoon. A rather sharp gradient in rainfall totals on Tuesday is expected from south to north, with little to no rain south of US-20, less than 0.2 inch for the interior lowlands south of Longview and the coast south of Tillamook, 0.25-0.5 inches for the SW WA Cascades and the coast from Tillamook to the state line, and 0.5-1 inch for Pacific County. Heavier rain associated with this atmospheric river is expected over the Olympic Peninsula. Expect another round of breezy southerly winds with gusts as high as 30-40 mph along the coast north of Tillamook and SW WA west of I-5 through this evening.

Upper-level ridging will reach its peak amplitude on Wednesday, supporting dry and unseasonably warm temperatures across interior valleys with high temperatures forecast in the low to mid 60s. Daily record high temperatures look to remain out of reach for most locations, though the record values of 64F at Portland (PDX) and Hillsboro (HIO) set in 1989 and 66F at Vancouver (VUO) set in 1904, 1907, and 1930 may be in jeopardy. However, showers will continue in Pacific County and along the coast north of Tillamook. Thursday is expected to be a transition day as upper ridging begins shifting east as upper troughing begins pushing into the northeastern Pacific. Daytime temperatures will lower a few degrees, though will still be unseasonably warm in the low 60s across interior valleys. Mostly dry weather is expected through the day except for a 20-40% chance of showers along the coast, mainly due to uncertainty on specific timing of the rain from the next approaching trough.

There is high confidence that an upper-level low pressure system will become situated over the northeast Pacific west of Canada from late Thursday/Friday into the weekend, returning troughing to the Pacific Northwest. Multiple surface frontal systems are expected to move through the region during this time, bringing repeated chances for widespread rain and breezy winds. There is still uncertainty with specific rainfall amounts and peak wind gusts; however, we can say for certain that it will be wet. This is shaping up to be another atmospheric river event as long-range ensembles indicate a 70-90% chance for vapor transport to exceed 500 kg/(ms) at the leading edge of this trough on Friday somewhere along the Oregon coast with similar probabilities of vapor transport values remaining above 250 kg/(ms) into Sunday. Increasingly saturated soils from multiple weather systems could allow for greater runoff into area rivers, meaning at least isolated flooding cannot be ruled out. People should also clear gutters and storm drains of any leaves or debris to prevent urban flooding. Across the Cascades, it appears that this system will be warm enough to keep snow levels between 5500-6500 feet, keeping the passes snow-free. However, Cascade peaks could see a few inches of snow combined between Friday night and Saturday night, with even more over the volcanoes.

When it comes to winds, there is a 20-40% chance for maximum wind gusts exceeding 55 mph along the coast Friday and Saturday, with the highest chances on Friday. Wind gusts of this magnitude could result in scattered or widespread power outages or tree damage. Along the I- 5 corridor, there is a 15-30% chance for maximum wind gusts exceeding 40 mph, which could result in isolated power outages or tree damage. To prepare, make sure to secure loose outdoor items. -03/10

AVIATION...Through 18Z Wednesday

A slow moving frontal band remains draped across Northwest OR and southwest WA, bringing persistent light to moderate rain to the region. Conditions vary across the are but most terminals are MVFR or IFR as rain impacts the terminals. Conditions are expected to improve for many terminals except KAST as the front shifts northward. Inland winds from the south 7-10 kts. Gusty southerly winds along the coast with gusts up to 25-30 kts.

Cloud cover overnight could thin enough to allow for some patchy fog but chances are low at 10-20%, mainly in the coast range. Will continue to monitor conditions for possible changes.

KPDX AND APPROACHES...Moderate to light rain continues as a frontal band sits over the region. Expecting this to shift northward early this afternoon but will continue to support MVFR or lower conditions for a couple more hours. Conditions trend toward VFR this afternoon. Winds southerly around 5-7 kt, shifting southeasterly this afternoon at less than 5 kt. -19

MARINE

Small craft conditions continue across the waters this morning in the wake of a frontal system. Winds will increase this morning across the waters and remain elevated through Wednesday as this system moves across the waters. There is a 60-90+% chance for gales north of Cape Falcon where a Gale Warning remains in effect from late this morning through Wednesday afternoon. South of Cape Falcon, there's only a 10-40% chance of gale force gusts through this evening, so have not opted for a Gale Warning. This evening through Wednesday, chances of gales increase between Cape Falcon and Cascade Head to 40-70%, so have kept the Gale Watch in place for zones PZZ253 and PZZ273 from this evening through Wednesday. A building west swell will increase seas to 14-19 ft around 14 seconds today into Wednesday. A Hazardous Seas Warning is in effect south of Cape Falcon beginning 1 PM today through Wednesday afternoon.

A stronger frontal system will increase winds and seas on Friday. with a 40-60% chance for Storm Force winds on Friday and a 60-80% chance of 20+ ft seas on Saturday. -03

BEACH HAZARDS

A moderate to high sneaker wave threat continues along the coast through this week as a westerly swell of 10-12 ft at 13-15 seconds increases to 14-16 ft midweek. This will result in waves running up significantly farther on a beach than normal, including over rocks and jetties. 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.

There is also the potential for tidal overflow flooding Tuesday and Wednesday as the tide plus anomaly are forecasted between 10 and 11 ft (MLLW). This could lead to further water inundation and coastal erosion.

Additionally, confidence is increasing that a stronger westerly swell of 20-24 ft with a dominant period at 16-18 seconds will impact the coast on Saturday for dangerous surf conditions. Destructive waves may wash over beaches, jetties, and other structures unexpectedly.

Extreme caution should be used if you plan to visit beaches this week. The 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. -03

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 10 AM PST this morning for PZZ210-251- 271.

Gale Warning from 10 AM this morning to 4 PM PST Wednesday for PZZ210-251-271.

Small Craft Advisory until 1 PM PST this afternoon for PZZ252- 253-272-273.

Hazardous Seas Warning from 1 PM this afternoon to 7 PM PST this evening for PZZ252-272.

Gale Watch from this evening through Wednesday afternoon for PZZ252-272.

Hazardous Seas Warning from 1 PM this afternoon to 4 PM PST Wednesday for PZZ253-273.