textproduct: Portland

SYNOPSIS

High pressure aloft will keep the pattern quiet and mostly dry into next week. Night and morning marine clouds will continue to be the main temperature wildcard, especially where clouds linger into midday. We may see another warming trend at the beginning of next week.

DISCUSSION...Now through Wednesday

This afternoon's weather was governed by the same split: steady ridging overhead, but marine influence near the surface. Now that the marine stratus inland has burned off as of 1 PM, expect clear skies and efficient warming through the rest of this afternoon and early evening. Into tonight, high clouds will move overhead, keeping overnight temperatures a degree or two warmer.

Friday and through the weekend, the most reliable part of the forecast is the overall dry pattern, with the less reliable part being exact high temperatures. Marine stratus will continue to re-form and surge inland overnight, potentially all the way to the Cascades, then gradually retreat back toward the coast during the day. Even so, guidance suggests a somewhat better chance for earlier clearing for many inland locations as the ridge axis moves overhead, which would support warmer daytime highs more consistently. Overall, expect coastal and higher terrain highs mainly upper 50s to upper 60s, with inland valleys generally 70s (locally low 80s where clearing is best on Saturday). As for Mother's Day (Sunday), while afternoon temperatures will be slightly cooler due to a shortwave trough sliding into the PNW, weather will continue to look favorable for outdoor plans with inland highs in the 70s and 60s elsewhere under a mix of sun and passing clouds.

The warmest and breeziest conditions remain favored in the Hood River Valley and the central Columbia Gorge, where overnight cloud cover is often less extensive and afternoon west winds are routinely strongest. Plan on afternoon winds 15-20 mph with gusts 25-35 mph in these areas Friday and through the weekend.

Friday still looks like the "dip" day as a weak shortwave glances over the top of the ridge. The main effect should be a bit more cloud cover and slightly cooler highs. Rain chances remain very low (less than 5%), and measurable precipitation is not expected.

By early next week, ridging quickly reasserts itself and the odds of warmer inland temperatures increase. Temperatures early next week will depend on the exact placement and strength of the ridge axis, farther west generally favors warmer outcomes locally, while a more inland ridge placement would keep temperatures a bit more cooler. Tuesday remains the primary day to watch as ensemble guidance continues to show substantial spread in potential temperatures. Current guidance suggests highs could range anywhere from the lower 70s into the lower 90s Tuesday, with similar broad spread lingering into Wednesday. Specifically for Tuesday, the warmer ECMWF ensemble members continue to suggest temperatures that would exceed the model's climatological extremes for early/mid May, though confidence in any specific outcome remains low at this time. ~12

AVIATION

BKN high clouds are streaming over NW OR and SW WA as a weak frontal system moving through the eastern Pacific pushes the high pressure east of the Cascades. Continuing onshore flow will support re-development of marine stratus along the coast with 60-80% chance for MVFR CIGs or lower along the coast at any given hour after 06-09z Fri through the end of the TAF period. The highest chances are between 12-18z Fri. Expect stratus along the coast to improve to VFR and clear by 20-22z Fri. Marine stratus may also filter into the southern Willamette Valley, resulting in a 25-40% chance for MVFR CIGs at KEUG after 09-12z Fri, increasing to 40-60% chance between 12-17z Fri. Expect conditions to improve to VFR by 17- 18z Fri. Winds will be light and turning more south-southwesterly after 06z Fri. Weak high pressure is expected to build over the coast Fri night, which would limit the return of marine stratus.

KPDX AND APPROACHES...VFR conditions with high clouds through the TAF period. Northwesterly winds 4-6 kt, becoming variable under 5 kt after 10z Fri. 10-20% chance for MVFR CIGs 12-16z Fri. -03/10

MARINE

High pressure offshore will maintain northerly winds through this evening. Tonight, winds turn southerly as a weakening front moves through the waters. Seas of 6-7 ft will gradually subside to 4-5 ft tonight through Friday night.

High pressure will re-strengthen offshore this weekend into next week, returning northerly winds. Chances for widespread gusts of 20-30 kt gradually increase each day from Saturday through Wednesday, breeziest south of Cape Falcon. The highest chances (70-90%) for at least isolated small craft wind gusts are from Monday to Wednesday. Seas re-build to 5-7 ft from Saturday morning through the middle of next week. -10

PQR WATCHES/WARNINGS/ADVISORIES

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