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

Marine stratus has really dissipated this afternoon inland, though coastal areas remain cloud north of KONP. Overall, most terminals are VFR with a few pockets of high end MVFR along the coast. This trend will persist through the next 8 hours or so as high pressure continues to build over the region. Overnight models are still struggling to get a grasp on exactly what we can expect. There are several possible outcomes, but based on climatology, the pattern, and some of our higher resolution models there will be a mixture of flight categories. Stratus development is still possible tonight though likely it will be high level for most locations aside from the southern Willamette Valley and coast.

Around 10Z Sat, models are suggesting anywhere from a 30-50% chance of MVFR to high end IFR CIGs from KEUG to KSLE with it dissipating by 18Z Sat. In conjunction, there is around a 20-30% chance of IFR VIS around KEUG and KONP. This effect would be from radiational cooling today if skies remain clear or thin enough overnight. The transition to northerly winds will also support this process.

KPDX AND APPROACHES...VFR through the next several hours. Overnight, confidence decreases on whether VFR or MVFR CIGs will dominate. At this point there are around equal chances for both outcomes. There is around a 20% chance of IFR CIGs as early as 12Z Sat but would be short lived if it does form. High pressure will cause the environment to clear out through the day on Saturday. -27

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.