textproduct: Portland

SYNOPSIS

High pressure remains the dominant feature through the weekend, keeping most locations dry with temperatures mostly controlled by reoccurring marine cloud development. A weak shortwave Sunday will knock temperatures down a bit. Early next week trends warmer again, though confidence drops quickly on just how warm it gets by Tuesday and Wednesday.

DISCUSSION...Now through Thursday

Low stratus that covered many areas earlier today has already mixed out, and inland locations are now seeing a brighter and warmer afternoon. Even so, temperatures still look a tad cooler than forecasted. The coast is a different story, with clouds still holding across some of the shoreline, keeping temperatures about 5-10 degrees cooler. This coast to inland contrast should persist into this evening as marine air remains in place near the surface, but the bigger point is that the day remains dry.

Expect low clouds to rebuild this evening and overnight and expand inland, then gradually erode back toward the coast late morning into afternoon. Guidance continues to favor somewhat better afternoon clearing for inland valleys compared to earlier in the week as the ridge axis shifts overhead, which supports warmer highs most days. For Saturday, expect afternoon temperatures in the upper 50s to upper 60s along the coast and higher terrain, with inland valleys generally low 70s to possibly 80.

Sunday (Mother's Day) brings a subtle change as a weak shortwave slides through. The most noticeable effect should be an increase in cloud cover and a slight cool-down, but the day still looks favorable for outdoor plans. Inland highs should generally hold in the low to mid 70s, while the coast and higher terrain remain in the upper 50s to mid 60s. Overall, conditions remain dry.

Heading into early next week, ensemble guidance increasingly supports ridging rebuilding and temperatures trending upward again. Where the ridge axis sets up will matter: a farther-west solution favors a stronger warm-up locally, while a more inland placement would keep temperatures elevated but less extreme. Tuesday remains the main day of concern from a forecast- confidence standpoint, as guidance continues to show large spread in the resulting high temperature. At this range, potential outcomes span from "pleasantly warm" to "unseasonably hot", with valley highs anywhere from the low 70s into the low 90s still on the table. Confidence in the overall warming trend and in the exact magnitude remains low. Guidance continues to diverge on how progressive the pattern becomes by midweek, which is why Tuesday/Wednesday highs still have a wide range of temperature values. While the temperature spread becomes narrower by Thursday, it still highly depends on the progression of the pattern next week. ~12

AVIATION

Westerly flow aloft continues as an upper level ridge of high pressure builds over the region. Marine stratus currently onshore across the north Oregon coast. As of 04z, lower VFR CIGs continue around FL035, while broken stratus with CIGs around FL050 are building over the northern Willamette Valley. There is around a 20-30% chance for MVFR CIGs between 11-15z Saturday in this area, while probs for MVFR have decreases to 20% or less across the southern Willamette Valley. The highest probability for for MVFR conditions exists along the central Oregon coast, including KONP, where there is a 50-60% chance between 12-18z Sat. Light offshore winds expected to turn northerly on Saturday while skies become mostly clear.

KPDX AND APPROACHES...Predominately VFR, with lowering CIGs overnight as stratus builds. There is a 20-30% chance for MVFR between 11-15z Saturday. Skies becoming mostly clear by Saturday afternoon. Northwest winds expected to persist around 3-6 kt. /DH

MARINE

Southwesterly winds over the waters today will transition to the north as high pressure develops on Saturday. Overall will see winds of 6 to 10 kt with gusts up to 18 kt. The highest winds will be in the central waters of PZZ253/273 with a 20% chance of seeing gusts up to Small Craft Advisory levels. Seas will reach around 4 to 6 ft at 12 seconds. Similar conditions persist through Sunday.

There is a shift on Monday as there is the potential for a low pressure system to move into the northeastern Pacific. Confidence is low at this point as there are a number of potential outcomes. However, at this time, we are expecting the northerly winds to persist and intensify on Monday with a trend towards Small Craft Advisory level speeds through Tuesday. This would be amplified by a surface ridge forming and thus seeing a typical summertime northerly wind speed paradigm. -27

PQR WATCHES/WARNINGS/ADVISORIES

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