textproduct: Portland

SYNOPSIS

High pressure over the Northeastern Pacific will continue to support dry and warmer-than-normal conditions across the region through much of the week. Onshore flow will maintain marine cloud cover and drizzle along the coast, and nightly pushes inland which will clear through the day. Chances increase for cooler and wetter weather Friday into Saturday, before becoming warm and dry again late this weekend.

DISCUSSION...Now through Monday

A consistent weather pattern will see similar conditions persist across the region through at least midweek. Broad upper-level ridging which spans the Northeastern Pacific and western CONUS will continue to favor largely dry weather and above-normal temperatures. Afternoon highs will remain in the upper 50s to upper 60s along the coast and in higher terrain, and in the upper 60s to upper 70s within inland valleys through Thursday. A low marine cloud deck will vary diurnally, with inland pushes each night bringing mist or drizzle to the coast and increasingly overcast skies inland, followed by a daytime withdrawal allowing skies to trend clearer. The timing and speed of the morning cloud burn-off will modulate afternoon highs; temperatures will likely rise higher than expectations if clearing occurs early, while a more persistent morning overcast will limit how high temperatures can reach that afternoon. Regardless, seasonably warm temperatures are only expected to result in heat impacts for those extremely sensitive to heat.

Consensus remains fairly high that an upper-level shortwave will ride over top of the ridge, bringing more seasonable temperatures and low to moderate chances for rain Friday into Saturday. Those chances remain only 25-45% at the highest along the coast and in higher terrain, and increasing to the north from around 10% near Eugene to 20% near Kelso/Longview along the I-5 corridor. Rain chances quickly drop below 5% east of the Cascade crest including the Hood River Valley and Central Columbia Gorge. The majority of ensemble members favor rain beginning at the coast sometime Friday afternoon, although any time from Friday morning to late Friday night remains possible, then moving inland within a few hours. Potential rainfall amounts remain very light, less than a tenth of an inch.

By the latter part of the weekend, long-range ensembles maintain that upper-level ridging will rebuild, yielding a return to warmer and drier weather for Sunday into early next week. At this point, there are 35-65% chances of reaching 80 degrees along much of the I-5 corridor on Mother's Day. -36

AVIATION

A continued southwest push has brought marine stratus well inland to the Cascade crest resulting in widespread MVFR cigs of 1.5-2 kft early this morning. High-end IFR cigs of 800-1000 ft are most likely (70-90% chance) along the central Oregon coast south of KTMK, including KONP, through the next 4-6 hours. Inland terminals are expected to improve to VFR by 19-21z Tue as low clouds largely mix out, while coastal terminals are more likely to remain MVFR until 21-23z Tue. Cloud cover at 2-3 kft will be more persistent along the coast, but coverage should fall low enough to see VFR conditions by the afternoon. Marine stratus will again push inland tonight, with MVFR/IFR conditions returning to the coast by 03-06z Wed, and cloud coverage increasing inland through at least 12z Wed.

Light winds of around 5 kt or less are expected throughout the period. South to southwest flow this morning will turn out of the west to northwest this afternoon, then back out of the south tonight.

KPDX AND APPROACHES...MVFR stratus in place at Portland-area terminals is expected to persist through around 20z Tue as increased mixing will tend to break up the cloud deck and raise cloud bases to 3-4 kft. VFR conditions will then prevail through the remainder of the period, with marine stratus redeveloping late in the period, after 06-09z Wed. Chances for further MVFR cigs reach 50% near 12z Wed. Light and variable winds this morning will build out of the northwest to near 5 kt this afternoon, then ease to light and variable again tonight. -36

MARINE

A continued southerly surge will bring persistent low stratus through Wednesday with chances for fog and/or drizzle during the overnight and morning hours. Southerly winds around 5-10 kt this morning will turn westerly and weaken to 5 kt or less this afternoon into tonight. Winds look to turn northerly late Wednesday through much of Thursday, before a weak system moving onshore Friday into Saturday will see southerly flow return with gusts of 15-20 kt and low chances for rain showers.

High pressure rebuilding this weekend will yield strengthening northerly flow, which may become hazardous to small craft late Sunday into Monday with gusts up to 20-25 kt. Chances for gusts to reach 21 kt or higher increase slightly from 20-60% on Sunday to 35-65% on Monday, with higher chances to the south.

Seas will remain fairly steady at 4-7 ft with a persistent westerly to northwesterly swell through this weekend. -36/23

PQR WATCHES/WARNINGS/ADVISORIES

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