textproduct: Portland

SYNOPSIS

Dry and warm weather is expected across the region through much of the week into the weekend with high pressure over the Northeast Pacific shifting east into the Pacific NW. Weak systems aloft may bring enhanced cloud cover on some days, but rain chances are minimal. Uncertainty in the forecast increases Sunday into early next week as chances for precipitation return for Memorial Day.

DISCUSSION...Now through Tuesday

Water vapor satellite imagery this morning shows an amplified upper level trough over the northeast Pacific with northwesterly flow streaming onshore. The GOES nighttime microphysics imagery reveals stratus along the coast, through the lower Columbia River Valley, and backbuilding off the Cascades into the Willamette Valley. Morning clouds are expected to scatter out by the afternoon allowing temperatures to warm again into the lower 70s inland and around 60 degrees at the coast. High pressure will maintain dry conditions through the end of the week.

As offshore ridging shifts east later in the week, temperatures will trend warmer, reaching the 60s to near 70 degrees on the coast and upper 70s to mid 80s inland. This will support widespread Minor HeatRisk excepting only the immediate coast. Chances for Moderate HeatRisk on Thursday are 15-35% in Portland and the adjacent northern Willamette Valley, 5-20% in Salem and Albany/Corvallis, and 5% or less elsewhere. Concerns for hazardous weather otherwise remain low. Temperatures on Friday are now trending only a degree or two cooler than Thursday as broad ridging moves over the region.

Saturday through the holiday weekend, uncertainty in the evolution and possible break-down of the upper-level ridge yields growing uncertainty in forecast temperatures and precipitation. In general, as the ridge deamplifies, temperatures are more likely to trend cooler through the period, especially by Monday. There continues to be greater consensus of an upper-level trough digging over the NE Pacific on Monday, supporting much cooler temperatures and 40-70% chances for rain across the area. This means there are increasing chances that a front brings widespread rain sometime on Memorial Day. Ensemble clusters still show quite a large range of potential rainfall, so will continue to see how models resolve the pattern into this weekend. -DH/36

AVIATION

Satellite imagery as of late Wednesday morning depicts MVFR stratus beginning to break out across the region. Stratus is breaking up faster across the central Oregon coast and central/southern Willamette Valley, while stratus across the Portland/Vancouver Metro Area and north Oregon coast will hold on through about 19-21z Wed. An upper level ridge offshore will support a return of northerly winds and VFR conditions with a FEW/SCT high clouds across the region from this afternoon through the end of the TAF period. North-northwesterly gusts up to 20-25 kt along the coast (strongest near KONP). For the Willamette Valley, north winds generally 10-15 kt except under 10 kt across the Portland/Vancouver Metro Area. Tonight, winds will weaken as pressure gradients ease, and there remains a 10-20% chance for MVFR stratus returning along the coast.

KPDX AND APPROACHES...MVFR stratus breaks out around 19-20z Wed. Afterwards, predominately VFR conditions through the TAF period. Northwesterly winds under 10 kt. -10

MARINE

High pressure continues offshore as northerlies are expected to persist through the end of the week. Strongest winds are expected during the afternoon and evening periods as the surface thermal trough strengthens over the northern CA/southern OR coast. More widespread wind gusts to 25 kt are expected later today and again on Thursday as inland temperatures warm. Small Craft conditions for most coastal water zones will persist each afternoon and evening. Seas 6 to 9 feet are expected through the week as well. A Small Craft Advisory is also in place for the Columbia River Bar for this morning due to strong ebb currents. Strong ebb currents are possible during the morning hours each day this week. The summer-like pattern is likely to break down later Sunday as a front approaches the waters by Monday next week. /DH

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory from 4 PM this afternoon to 5 AM PDT Thursday for PZZ252-271-272.

Small Craft Advisory until 5 AM PDT Thursday for PZZ253.

Small Craft Advisory until 5 AM PDT Thursday for PZZ273.