textproduct: Seattle/Tacoma

SYNOPSIS

Cool and cloudy conditions will continue into tonight. High pressure will nose back into the region on Wednesday for clearing skies and warming temperatures. Another round of increased cloud cover and stronger onshore flow is expected late Thursday into Friday as a dry front moves across the area. High pressure and offshore flow are on tap for the area late in the weekend into early next week.

SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/

Current forecasts are on track. Previous discussion follows with update to aviation portion. 27

Stratus remains draped across much of western Washington this afternoon, with temperatures remaining cool in the low to mid 50s. Cloudy conditions will continue through this evening, with cloud cover expected to gradually clear during the overnight period. Areas of fog will be possible in any areas of clearing overnight and a few isolated pockets of frost will be possible across the Chehalis Valley as temperatures dip into the mid 30s by early Wednesday.

High pressure will then build into the area on Wednesday and remain situated over the area into Thursday, allowing for temperatures to warm across the region. Afternoon highs will likely warm back into the upper 60s to low 70s by Thursday, bringing widespread Minor HeatRisk to areas primarily south of Everett and along the Cascade valleys. Outside of diurnal westerly winds through the Strait of Juan de Fuca, much of the Puget Sound region should see light northerly winds. Cloud cover will increase again late Thursday as a dry front approaches the area.

LONG TERM /FRIDAY THROUGH TUESDAY/

A dry front moving through the region late Thursday into Friday will bring increasing onshore flow and more cloud cover to the area again by Friday. Temperatures will cool a few degrees, topping out into the mid 60s for afternoon highs as a result. Skies will then clear and conditions will quickly warm up over the weekend, with temperatures near 80 possible by Sunday as high pressure builds back into the region and a thermal trough builds northward along the coast. Periods of offshore flow will develop as a result. Probabilistic HeatRisk guidance continues to suggest those temperatures corresponding to at least a 20-30% chance of the moderate category in the Seattle-Tacoma Metro area, with greater chances across the Southwest Interior.

High pressure over the region will keep temperatures warm into Monday, with Monday likely seeing afternoon highs similar to Sunday- in the upper 70s to low 80s. Temperatures then start to cool by Tuesday as onshore flow is reintroduced into the area.

AVIATION

North to northwest flow aloft continues into Wednesday as an upper ridge offshore gradually builds into the region. Light onshore flow near the surface will turn more northerly by Wednesday afternoon. Areas of MVFR ceilings are expected to reform along the coast overnight and locally inland from around KPWT westward. VFR is expected areawide from 18Z onward on Wednesday.

KSEA...Satellite trends suggest that VFR overcast will continue to thin this evening then scatter out overnight. VFR with mostly clear skies is expected on Wednesday. Surface winds light W/NW will shift N/NE overnight then become N/NW 7 to 10 knots Wednesday afternoon.

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MARINE

High pressure remains offshore with lower pressure inland, maintaining onshore flow. A stronger onshore push is forecast down the Strait of Juan de Fuca Thursday afternoon and evening with cold front.

Seas generally 5-8 ft today and tonight with some locations in the far outer waters increasing to 8-10 ft late tonight and early Wednesday morning. These spots are not expected to be large enough to warrant any SCA headlines at this time, especially since they're expected to be diminished by mid-morning. Otherwise, seas remain within the aforementioned range at least into Thursday afternoon.

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HYDROLOGY

No river flooding is expected over the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES

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