textproduct: Portland

SYNOPSIS

Rain returns by this evening as the progressive and active pattern continues. Through the workweek, repeated systems will bring cooler temperatures along with multiple chances for lowland rain and mountain snow to the region.

LONG TERM...Wednesday through Saturday

The active pattern continues through the latter half of the week as another trough looks to move inland late Wednesday into Thursday, however there remains significant uncertainty in its evolution, particularly whether it will follow a similar pattern of splitting into a cutoff low to the south, thereby leaving northwestern Oregon and southwestern Washington in a region of weak forcing and successive forecasts of lower precipitation amounts. As before, in the scenario of a more coherent trough affecting the region, the combination of cool air aloft and ample moisture could support impactful snow accumulations down to pass-level in the Cascades, although this is an unlikely solution at this point. Chances for 6 inches of snow Thursday through Friday at the Cascade passes is a mere 5%. Otherwise, seasonable temperatures with persistent 25-50% chances of rain showers are favored across the region through the workweek. Long-range guidance features low probabilities of another impactful system by next weekend. -36

AVIATION

Widespread IFR/LIFR flying conditions early this morning across the region with fog/mist and low stratus in place. The majority of terminals will continue to see severely restricted vis of 1SM or less through 16-18z Sun before improving. KSLE has maintained VFR vis so far through the overnight period, but there is a 50-60% chance vis will degrade to at least MVFR by sunrise. While vis quickly improves as fog/mist mix out, cigs will likely remain stuck at IFR/low-end MVFR levels for most terminals. Calm to light and variable winds early this morning will increase to 5-10 kt out of the south after 15-18z Sun.

A cold front arriving from the west will spread rain across the airspace from 15-21z Sun. At precipitation onset, increased mixing may actually improve conditions by lifting cigs at inland terminals, before chances for further IFR cigs increase after 06z Mon, while along the coast, persistent IFR cigs are expected. Winds will shift out of the northwest at 5-10 kt behind the boundary after 00-06z Mon.

KPDX AND APPROACHES...LIFR conditions within fog expected to persist through 16-17z Sun before improving. While vis may return to VFR levels, IFR cigs are likely to continue into the early afternoon. A cold front will arrive from the west, with rain beginning around 20z Sun and cigs potentially improving to MVFR at precipitation onset, although IFR cigs are again favored after 06z Mon. South winds around 5 kt through much of the day will turn out of the northwest behind the front. -36

MARINE

Seas of 7-9 ft at 13 seconds continue across the waters, but will build to 9-11 ft by this afternoon and further to 12-15 ft by Monday morning as a frontal system tracks across the region. A Small Craft Advisory therefore remains in effect as seas remain elevated through Monday evening. Another frontal system will traverse the waters Sunday evening into Monday, with initial southwest winds becoming northwesterly with gusts up to 25 kt behind the boundary, mainly for the outer waters. A building westerly swell will cause seas to rise to 12-15 ft by late Sunday night or Monday morning, before falling below 10 ft early Tuesday morning. Wednesday into Thursday, yet another system will see increasing winds and building seas across all waters. The robust swell expected mid to late this week has a high probability of exceeding 15 ft, but there is also a 25% chance of 20 ft seas and a 10% chance of 22 ft seas or higher. -42/36

PQR WATCHES/WARNINGS/ADVISORIES

OR...None.

WA...None.

PZ...Small Craft Advisory until 7 PM PST Monday for PZZ210. Small Craft Advisory until 10 PM PST Monday for PZZ251>253- 271>273.