textproduct: Portland

SYNOPSIS

Seasonably warm and dry conditions expected through the next week with morning clouds and afternoon clearing. Low chances for Cascade thunderstorms this afternoon, which may result in lightning with briefly heavy rain and erratic winds.

DISCUSSION...Now through Friday

Seasonable conditions with no weather impacts expected through the next week. The large-scale pattern looks to remain fairly stagnant through the period, with broad and relatively flat upper-level ridging over the majority of CONUS and weak positively-tilted upper 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.

A transient shortwave tracking overhead today yielded isolated light rain showers this morning, however dry conditions are expected through the remainder of the day west of the Cascades as the best forcing slides northward into Washington. The robust marine layer has thus far supported overcast skies, but latest satellite imagery depicts cloud cover beginning to erode, with increased sunshine expected through this afternoon. Above the low-level inversion, there is some available instability to generate high-base showers or thunderstorms, but those low chances (15-25%) are restricted to the Cascades where showers or storms may instead be surface-based. Any passing storms will be capable of producing lightning as well as briefly heavy rain and erratic winds. Chances for thunder fall below 5% this evening.

The next chance for light showers or Cascade thunderstorms appears to be on Monday when the next weak shortwave passes overhead, however the probability of accumulating rain is less than 5% away from the immediate Cascade crest. There is increasing consensus that upper-level ridging over the Rockies and Great Basin will build late in the workweek, which could favor warmer temperatures Thursday and Friday afternoons. A potential passing system Friday into next weekend will bring higher chances for rainfall, however uncertainty remains high at this lead time. -36

AVIATION...Through 18z Sunday

Widespread marine stratus west of the Cascades continues to support low-end MVFR cigs at 1.5-2 kft across the airspace late this morning. Modest clearing will see a trend to VFR cigs inland by 19-21z Sat and high-end MVFR cigs with a 40-50% chance of VFR cigs at coastal terminals by 21-23z Sat. Isolated rain showers have largely dissipated aside from along the Cascades, with the chances for rain or thunder now at 10% or less west of the mountains. Otherwise, hazy skies may continue to restrict slantwise vis while terminal observations maintain 7-10 SM at the surface. Light winds this morning will build to 5-10 kt out of the northwest this afternoon, then ease below 5 kt tonight.

KPDX AND APPROACHES...Low-end MVFR cigs below 2 kft are expected to trend to VFR as skies clear and cloud bases lift, with a 50% chance of VFR conditions by 20z Sat. West to northwest winds expected throughout the period, increasing to around 5 kt this afternoon, then easing tonight. -36

MARINE

A largely stagnant pattern continues through much of the next week with high pressure offshore supporting northerly to northwesterly winds of 8-15 kt and gusts up to 20 kt. Benign seas of 3-6 ft persist through the period. -36

PQR WATCHES/WARNINGS/ADVISORIES

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