textproduct: Portland

SYNOPSIS

High pressure continues over the region today with mostly dry conditions expected through Monday. Chilly temperatures expected Monday morning. A weak front will bring chances for light rain Monday night into Tuesday. Dry again on Wednesday. Active weather returns as a series of frontal systems bring increasing chances for rain later Thursday through the weekend. Seasonable temperatures continue through the week.

LONG TERM...Wednesday through Sunday

Ensembles are consistent in a high pressure ridge rebuilding on Wednesday. This ridge will aid in pushing the front eastward and keep conditions fairly "boring" through Thursday. Based on the global ensembles there is around a 10% of some light continued precipitation through the day on Wednesday but precipitation doesn't start ramping up until Thursday morning. This precipitation is expected to be light through the day but picking up overnight.

On Friday there is a trend towards yet another warm frontal system. This front is associated with a low pressure system over the Alaska Panhandle. Stratiform rain will fall with the GFS being the more robust system. With atmospheric warming this time of year there is generally a concern for Atmospheric River (AR) conditions. Based on the IVT values of both the GFS and ECMWF there is a trend to a low to moderate AR that will persist from the 4th through the 6th. When looking at the track, vectors are pointing straight easterly which would bode well for periods of heavy rain. Given the long duration, will have to consider watching for any flooding impacts. The GFS continues to be the most rain heavy scenario with around a 5% chance of 2-2.5" in 24 hours ending Saturday morning around Astoria, and less than a 5% chance of greater than 1.25" around Salem.

Rain persists through Sunday. I will note that some models are suggesting around a 10% chance of flooding after Sunday. However, these values are likely being triggered by the GFS that is running much higher than it's other global ensemble counterparts.-27

AVIATION

High pressure building offshore will maintain VFR conditions through the period. Lingering low stratus over the southern Willamette Valley is expected to dissipate by 00z Mon, yielding VFR conditions. Winds around 5 kt will continue out of the east to northeast for most, with northerly flow expected instead along the Willamette Valley. Some gusts of 15-20 kt are still possible to the west of terrain gaps, most notably including KTTD, however the offshore wind gradient is beginning to weaken and this stronger flow should wane this afternoon and evening. Relatively fry offshore flow and frost development tonight should preclude fog development at inland terminals.

KPDX AND APPROACHES...VFR conditions expected through the period with beneath largely clear skies. East to northeast winds around 5 kt will continue into tonight, turning increasingly out of the north-northwest at less than 5 kt by Monday morning. -36

MARINE

Benign weather continues across the coastal waters with weak offshore flow at 5-10 kt and seas of 5-8 ft. Building high pressure offshore will see flow turn increasingly out of the north through Monday night while seas remain around 5 ft. A weak front traversing the waters Monday night into Tuesday will see northwest winds increase to 15-20 kt while a long-period westerly swell will build seas to 9-11 ft on Tuesday. Winds and seas then ease midweek before a more active weather pattern develops late in the week. At this point, there are 25-40% chances seas rise above 10 ft again Friday into next weekend, but this potential hinges on the track and intensity of any potential weather system. -36

BEACH HAZARDS

A long-period westerly swell is expected along the northwestern Oregon and southwestern Washington coasts from late Monday through Wednesday next week. Wave heights increasing to 8 to 10 ft on Tuesday may not appear to present a safety risk to those on area beaches, but these energetic waves will present a moderate to high risk for sneaker waves, waves which can run significantly farther up a beach than normal, including over rocks and jetties. In addition, a period of perigean spring or "king" tides means these waves will have an even easier time reaching high up onto beaches, limiting the areas which may be safe from wave action.

A Beach Hazards Statement has therefore been issued from 7 AM Tuesday to 10 PM Wednesday. Sneaker waves can create potentially life-threatening conditions in the surf zone when beachgoers can be unexpectedly knocked off their feet and pulled out into cold ocean waters. Caution should be used when in or near the water, and those 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...None.