textproduct: Portland

SYNOPSIS

Light rain will spread over the region as a cold front pushes eastward. Lower chances of precipitation on Sunday as low pressure stalls off the northern California coast. There is moderate confidence in the pattern remaining cool and wet through next week as upper level troughing persists over the region, though there is low confidence is exact details at this time.

LONG TERM...Monday through Friday

There is decent agreement among ensembles that an anomalously deep upper level trough drops south out of Alaska, bringing colder air aloft to the region early next week. Upper disturbances will also produce periods of precipitation across the region. 850 mb temperatures are likely to be in the -3 to -6 C range, which is marginal for snow to the valley floor with onshore flow. The NBM maintains low probabilities for lowland conversational snow at around 1-10% overnight and early each morning with higher probabilities for elevations above 500 ft. Any snow that does accumulate would quickly melt as temperatures rise above freezing each day, thereby limiting potential impacts.

Confidence in snowfall totals over the Cascades remains low but trends support coinciding cold air and moisture which should bring healthy snowfall. Accumulation at pass level seems likely but exact timing and amounts are unclear so will continue to monitor the pattern for impacts. The latest guidance gives the best chances for exceeding 6 inches of snow during a 24-hr period for Thursday through Thursday night, at around 50-60% and 20-40% for 12 inches or more. This time period also corresponds with snow levels potentially falling to around 1500 ft. There is also a chance for snow to reach pass level in the Coast Range, mainly around highway 6 and 26. -19/DH

AVIATION

A cold front has pushed through the region with mainly scattered residual showers moving across the region at the moment. Plenty of low level moisture exists with widespread MVFR conditions across the area. With that said, a few sites have lowered into IFR and risen into VFR thresholds, but so far, both have been mostly temporary. Cooler temperatures aloft moving into the region should turn the lower atmosphere over and in theory should reduce the amount of 1000-1500 ft ceilings across the area, but given it should already be happening, becoming increasingly worried that it won't, and persistence and/or a gradual deterioration into IFR thresholds is what is on tap. In addition, roughly 50-60% of the high resolution model guidance suggests ceilings deteriorate into IFR thresholds from KUAO northward towards 15-18z Saturday. Either way, a warm front will spread steady light rain northward across the area Saturday. A combination of light low level northerly flow and hours of steady rain in the southern Willamette Valley should result in conditions trending into IFR thresholds late tonight into Saturday at KEUG.

KPDX AND APPROACHES...A cold front has pushed through the region with mainly scattered residual showers moving across the region at the moment. Plenty of low level moisture exists with a mix of high end IFR and widespread MVFR conditions around the Portland metro. Cooler temperatures aloft moving into the region should turn the lower atmosphere over, but given it should already be happening, increasingly worried that it won't, and persistence and/or a gradual deterioration into IFR thresholds is the more likely outcome overnight. In addition, 50-60% of the high resolution models suggest ceilings will lower into IFR thresholds at KPDX towards the 15-18z Saturday time period. Will hold off from putting into the TAF just yet as our best statistical guidance still shows the probabilities closer to 10-20%.

MARINE

Today has been a bit more complicated as the cold front that we had been waiting for stalled over the waters causing winds to increase and created a stronger westerly swell. Seas ended up building to 17 ft at 16 seconds at a number of buoys this morning, with the outer buoys still reporting similar heights. These heights have trended towards the 90th percentile for some of our models. There is a general trend of a slow decrease in wave heights behind the front, but due to it's slow progress, those heights may linger longer than currently forecast. Winds are non-impactful at this time with gusts generally below 20 kt.

As the front exits, winds will become northerly though the background swell remains west-northwesterly. Based on high resolution models, there is around a 20% chance of gale force winds in the southern waters of PZZ273 on Saturday evening into Sunday morning. The next period of concern lies on Thursday as another strong front moves over the waters. There is a 25-35% chance of gale force winds on this day at this point.-27

BEACH HAZARDS

A high threat for sneaker persists through Sunday evening due to a long period westerly swell. Waves can run up significantly farther on a beach than normal, including over rocks and jetties. Sneaker waves can suddenly knock people off of their feet and quickly pull them into the frigid ocean which may lead to serious injury or drowning. Caution should be used when in or near the water, especially those who will be razor clamming. Keep children and pets away from the surf zone. Keep off of jetties, rocks and logs near the surf zone. If you see someone swept into the sea do not swim in after them. Call 911 and keep an eye on them until help arrives. -10

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 4 AM PST Saturday for PZZ210.

Small Craft Advisory until 4 PM PST Saturday for PZZ251>253.

Small Craft Advisory until 4 AM PST Sunday for PZZ271>273.