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SYNOPSIS

A fast moving cold front will cross over the region through this morning. This will bring a return of light rain across northwest OR and southwest WA. Temperatures cool down behind this system, dropping snow levels towards 4000 ft by Sunday night, resulting in light snow through the Cascade passes. Expect a chilly Monday night into Tuesday morning. The next system arrives Tuesday night into Wednesday, with wet weather continuing through the end of the week. Looking beyond and into the start of December, some models are hinting at winter weather across the forecast area. However, there is a wide range of model solutions and the forecast will change.

LONG TERM...Tuesday through Saturday

Tuesday morning will be the chilliest night of the week, with low temperatures forecast to drop into the low to mid 30s across interior lowland valleys. With moist surface conditions, there will be potential for frost development Monday night into early Tuesday morning especially on grasses and elevated metal surfaces. By late Tuesday afternoon and evening, the majority of ensemble members suggest upper level ridging will build over the U.S. West Coast, however, the Pacific Northwest appears to be right at the top of the ridge. While 500 mb heights will climb and bring relatively warmer temperatures, we will be far from dry.

The next system will ride the periphery of the ridge and enter the Pacific Northwest from the northeastern Pacific. This will bring widespread rain back into the forecast Tuesday into Wednesday. This system is expected to be on the warm side with 850 mb temperatures around 2-4 C. As a result, snow levels will climb above 6000 ft. Conditions remain showery through the latter part of the week as this system moves through the region.

Chances for 48-hour liquid precipitation exceeding 1" from 4 AM Tuesday to 4 AM Thursday are around 45-80% along the coast, Coast Range, Willapa Hills, and Cascades, 20-50% across the Willamette Valley, southwest WA lowlands and Upper Hood River Valley. Similar, 48-hour liquid precipitation exceeding 1" probabilities are forecasted from 4 AM Wednesday through 4 AM Friday.

Ensemble members maintain wet weather through the end of November and into the start of December. However, there is a lot of uncertainty as to how exactly how the end of November/start of December will greet the Pacific NW. At this time, the 06Z deterministic GFS is bringing -8 to -17 C (18 to 1 F) 850 mb temperatures into the CWA. Looking at the 06Z deterministic ECMWF is bringing -2 to -7 C (25 to 19 F) 850 mb temperatures. So, when looking at any forecast for the end of November into the start of December, be aware that uncertainty is high. With that in mind, now is the perfect time to make sure that your are ready for any winter weather. /42

AVIATION

Expect a mixed bag of LIFR/IFR/MVFR/VFR flight conditions today and tonight, with MVFR conditions being most prevalent. A slow-moving frontal boundary will continue moving over southwest WA and northwest OR today, bringing light rain and/or drizzle to all terminals much of the time through 00-03z Monday. Precipitation should end from west to east after 03z Monday as the aforementioned front shifts over the Cascades. Note there will likely be a brief period of improvement to either high-end MVFR cigs or low-end VFR cigs between 04-10z Monday, before cigs likely lover again after 10z.

KPDX AND APPROACHES...Expect periods of light rain/drizzle and MVFR cigs to continue through approximately 04z Monday, with surface visibilities fluctuating between 2 and 4 SM. After 04z Monday, there is a 70% chance cigs will temporarily lift to 3500-4000 ft before lowering back to MVFR thresholds around 10z Monday when probabilities for cigs below 2000-3000 ft increase to 60%. Cannot rule out IFR cigs below 1000 ft at that time either, however this is not the most likely outcome. -23

MARINE

High pressure over the area is maintaining fairly stable conditions with minimal change expected through Sunday. Seas will remain around 10 to 14 ft through the remainder of the weekend before falling to 8 to 9 ft Monday afternoon and then 6 to 8 ft on Tuesday. A weak cold front will move over the waters Sunday morning, bringing southwest becoming northwest wind gusts up to 25 kt. A relatively stronger front arrives Tuesday night into Wednesday, bringing wind gusts up to at least 25-30 kt with a 30-50% chance for gale force wind gusts up to 35 kt. Confidence in gale force wind gusts materializing is not high enough to issue a Gale Watch at this time. /42-23

BEACH HAZARDS

An energetic westerly swell is expected along the northwestern Oregon and southwestern Washington coasts through Monday. Seas 10-14 ft at 14-16 seconds are forecast and resulting in a high sneaker wave threat. These energetic waves can run significantly farther up a beach than normal, including over rocks and jetties, creating potentially life-threatening conditions in the surf zone when beachgoers can be unexpectedly knocked off their feet and pulled out into cold ocean waters.

A Beach Hazards Statement has therefore been issued through 10 AM Monday. Caution should be used when in or near the water, and beachgoers with children should be especially watchful. Never turn your back on the ocean, and be sure to keep an eye on the waves. Those participating in razor clam digs should additionally exercise caution. /42

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 10 AM PST Monday for PZZ210-251>253- 271>273.