textproduct: Portland

SYNOPSIS

Zonal flow with dry conditions through Monday. Warming temperatures to near climatological normals. Frontal system moves in on Tuesday bringing widespread rain and breezy south winds. Precipitation continues through Wednesday before tapering off late in the week. Continued warming over the weekend before another system arrives on Sunday.

LONG TERM...Wednesday Night through Sunday

Wednesday night the frontal system will exit the area with lingering showers and lowering snow levels. Cold air continues to filter in aloft through Thursday with 850 mb temperatures around -4 to -5 deg C. With any lingering precipitation, we will see snow in the Cascades. Models continue to show around a 10% chance of snow levels down to the valley floor, however, the chances for precipitation is still quite low. Even if snow were to fall at the lower elevations, the road temperatures will be warm enough that accumulation is not expected.

By Thursday afternoon into Friday, the weather system is expected to move out of the area with upper level flow becoming more zonal. Expecting dry conditions with clearing skies by midday Thursday, which could allow for temperatures to warm into the upper 50s on Thursday and into the low to mid 60s for Friday and Saturday for the interior lowlands. Saturday is expected to be the peak day of the warming trend, and NBM indicates a 20-30% chance of temperatures reaching 70 degrees across the Willamette Valley.-27/03

AVIATION

Dry conds and westerly flow aloft will continue through the TAF period, maintaining high clouds and VFR conds. Winds will keep northerly to northwesterly through the TAF period for all terminals. Winds at most terminals will remain under 8 kt, except for KAST and KONP where winds may remain around 10 kt with gusts up to 20 kt until 06-08Z Mon. Winds will become light and variable after 09Z Mon, which paired with cloud breaks may result in Mon morning temperatures dropping to the low to mid 30s across the Willamette Valley, leading to potential frost development over metal surfaces between 09-16Z Mon.

KPDX AND APPROACHES...VFR conds through the TAF period. Northwesterly winds around 6-8 kt as of 04Z Mon will weaken overnight, resulting in light and variable winds by 07-09Z Mon. These light winds and clear skies support the potential for frost development over metal surfaces between 09-16Z Mon. ~12

MARINE

High pressure over the waters will maintain northerly winds through Monday. The next strong ebb will occur around 818 AM Sunday, so a Small Craft Advisory has been issued for the the Columbia River Bar between 6-11 AM Monday as the ebb builds seas around 7 to 8 ft along the Main Channel of the Bar.

A weak thermal trough has developed along the southern Oregon coast this afternoon which will last through early Monday morning. This is tightening pressure gradients across the waters south of Cape Falcon and leading to breezier northerly winds with gusts up to 25 kt. A Small Craft Advisory remains in effect for all waters south of Cape Falcon through at least 5 AM Monday. Northerly winds may last longer for the outer waters beyond 10 NM offshore, so the Small Craft Advisory for these zones will go through 8 AM Monday. Seas build to 7-10 ft at 11 sec as wind waves increase from the breezy northerly winds.

The next robust weather system returns Tuesday into Wednesday. This system will bring a return of breezy southerly winds across all waters. Current guidance suggests a 40-60% chance for widespread and frequent Gale force wind gusts of 34 kt or greater on Tuesday, with the highest chances beyond 20 NM offshore. Latest guidance suggests the strongest winds occur between 8 AM to 5 PM Tuesday. Due to increasing confidence, a Gale Watch has been issued for all waters including the Columbia River Bar from 5 AM to 11 PM Tuesday. Seas on Tuesday and Wednesday are also expected to build to around 12-15 ft in response to increasing wind waves along with an increasing westerly swell. There's a 25-50% chance seas could exceed 15 ft with a 2-6% chance for seas exceeding 20 ft. Chances increase from south to north, peaking across the waters north of Cape Falcon and mainly beyond 40 NM offshore. -10/03

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory from 6 AM to 11 AM PDT Monday for PZZ210.

Gale Watch from late Monday night through Tuesday evening for PZZ210-251>253-271>273.

Small Craft Advisory until 5 AM PDT Monday for PZZ251>253-271.

Small Craft Advisory until 8 AM PDT Monday for PZZ272-273.