textproduct: Portland

SYNOPSIS

Seasonably warm and dry conditions expected through much of the week with morning clouds and afternoon clearing. Winds generally out of the west to northwest, strongest in the afternoon and along the Central Columbia River Gorge and Upper Hood River Valley. Next best chances for light rainfall arrive Friday into next weekend.

DISCUSSION...Now through Saturday

Seasonably dry and warm conditions continue through the week with minimal weather impacts. The large-scale pattern remains fairly stagnant through the period, with broad and relatively flat upper-level ridging over the majority of CONUS and a weak, positively-tilted upper- level troughing over the northeast Pacific. This pattern will support continued onshore flow, maintaining near-normal daily high temperatures in the 80s within inland valleys and 60s along the coast, and overnight lows in the 50s across the region. Mornings will be characterized by clouds, especially along the coast, which will tend to clear by the afternoon. Light west to northwest winds will, peaking each afternoon. The strongest winds are likely to be along the Central Columbia River Gorge and Hood River Valley, but impacts are not anticipated.

The majority of ensemble members are in agreement that upper- level ridging over the Rockies and Great Basin will build late in the workweek, which would favor a brief warm-up on Thursday. However, ensemble guidance shows the upper-level trough over the northeast Pacific shifting onshore Friday into the weekend, resulting in slightly cooler temperatures and winds coming from the west to southwest. Chances for precipitation also increase to 10-30% across the region during this time, however, there is still high uncertainty in the timing and potential rain amounts. A weaker front at the end of the week would have a hard time counteracting the dry airmass in place and make accumulating rainfall unlikely. -10/36

AVIATION...Through 00z Tuesday

Earlier marine stratus has largely cleared this afternoon, aside from the areas around Grays Harbor and the mouth of the Columbia River including KAST, but further clearing should favor VFR flying conditions with sct low clouds into this evening. Elsewhere, largely clear skies beneath sct high cirrus coverage will also continue to support VFR conditions. North to northwest winds of 5-10 kt at inland terminals and 10-15 kt with gusts up to 20 kt along the coast will ease below 5 kt by 06-09z Mon.

Additional low stratus is expected to develop along the coast and push inland tonight, with some uncertainty in cloud coverage within interior valleys. There is high confidence in MVFR/IFR conditions (70-90% chance) at coastal terminals by 09-12z Mon, but only 50-60% chances after 12z Mon inland. Any low clouds will begin to mix out by 17-18z Mon inland, while persistent MVFR cigs are more likely along the coast. North to northwest winds will again build to 5-10 kt inland and 10-15 kt gusting 20-25 kt at coastal terminals by 18z Mon.

KPDX AND APPROACHES...High confidence in continued VFR conditions beneath sct high clouds through 06-09z Mon. Chances for MVFR cigs then increase as low stratus pushes inland, reaching 50-60% from 12-17z Mon before low cloud mix out by the late morning. Diurnal northwest winds ease below 5 kt by 06-09z Mon, then build again to 5-10 kt by 18z Mon. -36

MARINE

A largely stagnant pattern continues through much of the week with high pressure offshore supporting northerly to northwesterly winds of 8-15 kt and afternoon gusts up to 20 kt. Weak low pressure moving over the northeast Pacific Friday into next weekend will shift winds out of the west to southwest across the waters, but chances for gusts exceeding 21 kt remain low, only 5-10%. Benign seas of 3-6 ft persist through the period. -10/36

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...None.