textproduct: Portland

SYNOPSIS

Dry weather has returned across northwest Oregon and southwest Washington following the atmospheric river event. Several rivers remain in action stage but will continue to subside today as dry weather prevails. A high pressure ridge will build over the northeast Pacific Ocean and move overhead by Monday, warming temperatures into the mid to upper 60s throughout next week. Precipitation chances also continue as an atmospheric river rides the northern periphery of the ridge. The bulk of the rain is forecast to track toward western British Columbia and northwest Oregon, with lighter amounts over our area.

SHORT TERM...Now through Monday night

Satellite imagery and surface observations as of early Saturday afternoon depicts predominately dry weather with scattered clouds as high pressure re-builds following our atmospheric river event.

An upper level ridge will amplify over the the northeast Pacific Ocean on Sunday and shift over the Pacific Northwest by Monday. This will maintain predominately dry conditions across northwest Oregon and southwest Washington as we head into early next week. Above-average 500 mb heights will also set-up over our area, resulting in a warmer air mass and high temperatures in the mid to upper 60s across interior valleys. Despite the warmer weather, we can't rule out the possibility for rain. Moisture associated with an atmospheric river will ride the northern periphery of the ridge and make landfall into western British Columbia and far northwest Washington. While the bulk of the rain appears to track further north of our area, some model solutions have the southern periphery of the atmospheric river bringing at least some light rain into far northwest Oregon and southwest Washington. Precipitation chances still linger during this time, with the highest chances (40-60%) along the coast and southwest Washington. Given the light precipitation amounts, minimal impacts are expected at this time but will need to monitor this over the next few days. -10

LONG TERM...Tuesday through Friday

The long term forecast will ultimately be defined by how amplified the aforementioned upper level ridge will be. Tuesday through the end of the week, the majority of ensemble members remain in agreement that the bulk of the precipitation from the atmospheric river riding the northern periphery of the ridge will continue to trek towards Vancouver Island and the Olympic Peninsula. In this scenario, we would continue to see renewed chances for precipitation across northwest Oregon and southwest Washington, but the light precipitation amounts would lead to minimal impacts. If the ridge ends up flattening as it moves eastward, then we could see this atmospheric river track further south and lead to increased precipitation amounts over our area, thus increasing the potential for impacts. This is currently not the most likely scenario, but we'll continue to closely monitor the progression of this set-up. The latest NBM guidance suggests that the wettest scenario (10% chance for occurring) for a 72 hour total ending 5 AM Friday is around 2-3 inches along the coast from Tillamook to Pacific County, WA, 1-2 inches across the Portland Metro Area through Cowlitz County, and less than 1 inch everywhere else.

While there is still some uncertainty whether or not precipitation will make it's way to our area from the north, there is higher confidence that above-average 500 mb heights will continue throughout the week, maintaining spring-like temperatures with high temperatures in the mid to upper 60s for interior valleys (potentially 70 degrees the further south you are). By the end of the week (Friday), NBM guidance suggests a 15-20% chance for high temperatures exceeding 75 degrees across the central/northern Willamette Valley, with higher chances of 40-60% across the southern Willamette Valley. Given the warmer temperatures, we could see some increased snowmelt across the Cascades. -10

AVIATION

Northwest flow aloft with mainly dry conditions expected today and tonight. This will promote predominately VFR conditions through the TAF period with decreasing clouds through this evening. Increasing moisture Sunday morning will bring mid to high level clouds, but rain is not expected. North to northwest winds around 5-10 kt ease tonight.

KPDX AND APPROACHES...VFR with scattered mid to high level clouds expected through the TAF period. Northwest winds around 4-8 kt ease overnight. /DH

MARINE

High pressure building over the coastal waters today will maintain northerly winds around 10-20 kt. Isolated gusts up to 25 kt will be possible through this evening. Seas remain relatively steep around 7 to 8 ft at 8-9 seconds, so will maintain the Small Craft Advisory through 5 PM today. Winds turn offshore by early Sunday as an offshore weather system moves toward Vancouver Island. Seas subside to around 4 to 5 ft on Sunday with relatively benign conditions expected through Sunday night.

Southerly winds return next week, increasing on Monday and likely remaining elevated through the middle of the week as a quasi- stationary front remains offshore. While winds are expected to be breezy, probabilities for gales is generally less than 15%. Seas build back to around 10 ft. /DH

HYDROLOGY

Dry weather has returned, ending the threat for additional flooding due to excessive rainfall. The only Flood Warning that remains in effect is for the Cowlitz River at Kelso, which has crested and is gradually subsiding. This river is expected to fall below Minor Flood Stage by early Sunday morning. Several other rivers across far northwest Oregon and southwest Washington remain in Action Stage, but will continue to subside as dry weather prevails. -10

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 5 PM PDT this afternoon for PZZ210- 251>253-271>273.