textproduct: Portland

SYNOPSIS

High pressure persists through Tuesday with rising temperatures each day. Moderate HeatRisk along the I-5 Corridor north of Salem including the Portland/Vancouver Metro on Monday and Tuesday. Weak shortwave and mesoscale low pressure today will cause winds to increase over the waters and along the coast. Filling low pressure moves near the coast starting Wednesday. Zonal flow through Friday. Low pressure intensifies on Saturday with increasing chances for rain.

LONG TERM...Wednesday through Saturday

There is relatively high confidence that temperatures cool back into the 70s on Wednesday and persist through the end of the week, remaining near to slightly above average temperatures for early June. Models and their ensembles are in fairly good agreement that a low pressure system in the NE Pacific weakens as it moves toward the Gulf of Alaska on Wednesday. An associated frontal band well ahead of the surface low will approach the coast, but guidance continues to trend down with minimal, if any, precipitation spreading inland. In fact, NBM guidance generally shows less than a 10% chance of rain through Thursday. But, there remain a handful of ensemble members that do show some QPF, so we cannot rule out some precipitation yet.

Within the long-term forecast, there is great uncertainty regarding a potential low pressure system. Based on the ensemble low pressure center outputs, several members are bringing a cool air wrapped low pressure system down from the Gulf of Alaska and it skirts the Washington coastline. At this point, the number of models that show some kind of an advecting trough less less than 40% and therefore, confidence is low. Despite the potential pattern shift, onshore flow is likely which will usher in cooler marine air and thus temperatures will be lower. The overall spread between the 10th to 90th percentile (essentially the coolest and warmest scenario) is only 10 deg F ranging from around 65-75 deg F in the lowlands with little to no change along the coast. The big question is in regards to precipitation accumulation where the spread is much greater. For example, in Tillamook, the 10th percentile (dry scenario) shows 0.00 inch of rain, where the 90th percentile (wet scenario) is close to 1.0 inch. Therefore again confidence is low. -27/DH

AVIATION

Surface high pressure centered offshore will maintain VFR conditions across the airspace. Patchy remaining low clouds this morning will erode by 19-20z Sun, yielding clear skies into tonight. Rising diurnal winds will become gusty by 20-22z Sun, reaching 15-20 kt with gusts to 30 kt along the coast and 10-15 kt with gusts to 20-25 kt inland out of the north to northwest. Terrain will shield east-west oriented gaps from the wind, so the Columbia Gorge including KTTD will see lighter flow below 10 kt out of the northwest. Winds aloft will turn offshore tonight, while surface winds ease to 5 kt or less out of the north to northeast. Marine stratus is favored to remain west of coastal terminals given incipient offshore flow.

KPDX AND APPROACHES...VFR conditions beneath largely clear skies expected throughout the period. Diurnal northwest winds will rise to 10-15 kt with gusts of 20 kt after 20-21z Sun, then ease below 5 kt late this evening, after 06z Mon. -36

MARINE

High pressure builds through Tuesday which will lead to a typical summer like pattern. High pressure will start to move eastward which will result in increasing northerly to northwesterly winds across all waters. At the surface there is also an additional shortwave trough which, when combined with the overarching pattern, will increase winds over all of the waters. Northwesterly winds will be highest south of Cape Foulweather OR where gusts will reach up to 30 kt. Small craft advisory speeds are still expected over all of the waters though they will increase gradually from south to north. The northern waters will sit right along the thresholds so the spread of gusts up to 25 kt will be inconsistent. These winds are already beginning to pick up south of Cape Foulweather and will peak this afternoon. Seas will be comprised of a northwesterly primary swell and the northerly wind wave. Some areas may see seas of 10 ft but most guidance suggests combined wave heights below that thresholds.

The ridge continues to shift eastward and intensify through Tuesday but overall will have minimal impact to the marine environment. A pattern change expected on Wednesday as a series of systems look to dive down out of the northeastern Pacific through the latter part of next week, but minimal impacts are expected with these systems at this time. -27

PQR WATCHES/WARNINGS/ADVISORIES

OR...None.

WA...None.

PZ...Small Craft Advisory from 2 PM this afternoon to 2 AM PDT Monday for PZZ251-271.

Small Craft Advisory from 2 PM this afternoon to 5 PM PDT Monday for PZZ252-272.

Small Craft Advisory until 5 PM PDT Monday for PZZ253-273.