textproduct: Portland

SYNOPSIS

Calmer conditions are expected the next several days with lingering shower chances primarily pinned across the Coast, Coast Range, and the terrain of southwest Washington and far northern Oregon. Rain chances then shift to central Oregon Saturday into Sunday as a weather system moving into northern California brushes the region, but confidence is only low to moderate on the exact northern extent of precipitation. Completely dry weather then returns early next week. Conditions likely remain within typical climatological normals through the forecast period with no significant weather impacts on the horizon.

DISCUSSION...Wednesday afternoon through Tuesday

Visible satellite imagery early Wednesday afternoon shows morning fog and stratus has dissipated with scattered mid-level clouds streaming over the region. A few scattered showers are moving through SW WA and far N OR this afternoon, mainly over the terrain, though with limited accumulation. Colder air from Canada has funneled into SW WA and N OR today. High temperatures are expected to peak right around 50 degrees for the lowlands, but the overnight temperatures will be on the cooler side. There's a 60-90% chance for low temperatures to fall near to below freezing by tomorrow morning for the interior lowlands, though locations that see continued cloud cover through the nighttime hours will likely not fall quite so low. This will lead to another round of widespread frost in the overnight to morning hours. Additionally, any shower that moves off of the terrain and over lower elevations could produce light snow or a rain/snow mix, especially for elevations above 700-1500 feet. Accumulating snow is not expected (less than 5% chance). Fog also remains a possibility in the morning hours, though some locations may end up more frosty than foggy.

As upper level flow remains fairly zonal through Friday, shower chances with limited impacts will continue through Friday morning generally for SW WA and the far N OR Coast, Coast Range, and Cascades. The weather is expected be fairly consistent over the next few days with high temperatures in the 50s for the lowlands, low temperatures in the low to mid 30s, foggy and/or frosty overnight and morning conditions, and otherwise dry conditions.

Ensemble guidance remains in sync with a cut-off low pressure system moving inland from the west over northern California Saturday into Monday. There still remains a fair bit of uncertainty on how this system will impact NW OR dependent on the north/south track of the low. If it approaches the coast closer to the CA/OR border, precipitation chances could spread as far north as the Salem area with slightly higher precipitation amounts in Lane County. However, if it approaches the coast closer to central CA, then our forecast area could remain completely dry. Looking at ensemble members, more than half indicate the low will be north enough for at least precipitation chances in Lane County, especially for the Cascades. Either way, not expecting impacts from any precipitation from this system. The temperature forecast will also be impacted by the track of this low. The farther north it tracks, more clouds will push north into N OR and SW Washington, limiting daytime warming and nighttime cooling. A southern track will allow for clear skies, warmer daytime temperatures, and colder overnight temperatures near to below freezing in the interior lowlands. Probabilities for temperatures falling below freezing continue dropping in the interior lowlands, now around 20-40% through Sunday morning, except for up to 50-60% for the SW WA lowlands and Cascade foothills.

Transient ridging returns to the PacNW for Monday and Tuesday, leading to dry weather and increasing daytime temperatures. By Tuesday, daytime highs are expected to peak in the upper 50s to low 60s. These will be great days to squeeze in outdoor activities before rain returns with a benign springtime weather system on Wednesday. -03

AVIATION

Currently VFR throughout most of the airspace. Expect these conditions to persist through 06-12Z Thursday, after which fog development may occur. While light winds continue, which often supports fog development, any fog development tonight will likely be more patchy than widespread. With current model guidance, there remains low to moderate confidence for fog develop between 06-12Z and 18Z Thursday (25-35% chance of LIFR conditions). For coast terminals, there is a 20-30% chance for MVFR conditions after 06Z Thursday. Otherwise, expect light and variable winds through the TAF period.

KPDX AND APPROACHES...Expect VFR conditions and light winds through most of the TAF period. The only exception is from 09Z to 18Z Thursday, where guidance suggests chances for foggy conditions (20-30% chance of LIFR conditions). ~12

MARINE

Calm seas and winds, with bouy observations this afternoon showing seas around 4 to 6 ft at 9 to 10 seconds with wind gusts around 10 to 15 kt. Headed into Thursday, seas will remain below 8 ft with wind gusts holding between 10 to 20 knots (highest over the outer waters north of Cape Falcon). Local guidance shows a mixed bag of swells with a primary northwesterly swell and a southerly fresh swell, with primarily southerly through Thursday then northwesterly through the rest of the week. Expect widespread seas near 10 ft on Friday into Saturday. The seas ease back down again starting Sunday and into the work week, lowering to around 5 to 7 ft. ~12

PQR WATCHES/WARNINGS/ADVISORIES

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