textproduct: Seattle/Tacoma

SYNOPSIS

Low level onshore flow with southwesterly flow aloft today. Convergence zone dissipating midday. Upper level low west of Haida Gwaii this morning will slowly move southeast through tonight. Upper level disturbance spinning out of the low moving through Friday. Upper level low moving over Western Washington Saturday moving east Saturday night. Temporary upper level ridge Sunday. Another upper low will move through the first part of next week for more showers and cool temperatures.

SHORT TERM /TODAY THROUGH SATURDAY/

Satellite imagery shows cloudy skies over Western Washington early this morning. Doppler radar has showers over Snohomish and Northern King County associated with a convergence zone and some lingering showers over Whatcom county. Temperatures at 3 am/10z were in the 50s.

Convergence zone remaining in place and continuing through the morning hours before fizzling midday. Western Washington in between features today. Southwesterly flow aloft bringing high cloud cover to the area while low level onshore flow will keep the lower levels moist at least through the morning hours. Highs in the 60s and lower 70s.

Upper level low moving slowly south off the British Columbia coast tonight. Upper level shortwave spinning out of the low approaching the coast overnight with a chance of showers along the coast and over the Northwest Interior. Lows in the mid 40s to lower 50s.

Shortwave moving through Friday in the afternoon keeping at least a chance of showers in the forecast. Increasing southwesterly flow aloft will create a rain shadow centered near Everett in the morning before it fills in the afternoon. Clouds and showers with highs only near 60.

Upper level low approaching Western Washington Friday night will move inland Saturday keeping showers in the forecast. Convective indices lining up for isolated thunderstorms Saturday. Lifted indexes still in the 0 to -3 range, 500 mb temperatures -25C to -29C, convective temperatures in the mid 50s and CAPE between 300 and 600 J/KG. Lows in the mid 40s to lower 50s. Highs like Friday near 60. While both Friday and Saturday high temperatures are well above record low maximum temperatures for the day this time of year there is only about a 10 percent chance in Seattle of getting a high in the 50s. Felton

LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/

Low weakens to a trough and exits the area Saturday night. Extended runs showing pretty good run to run consistency with a temporary upper level ridge moving through Sunday for a brief break in the showers. Another cool upper level low dropping down out of the Gulf of Alaska a little slower on the current run with the low not moving inland over Oregon until Tuesday. Still the potential for wrap around moisture Wednesday as the low moves slowly east. At least a chance of showers in the forecast Monday through Wednesday. Temperatures remain below normal with highs in the lower to mid 60s. Lows in the mid 40s to lower 50s.

AVIATION

Post-front convergence showers continue this morning in portions of the north sound, Cascades, and North Interior. Flow aloft will increase from the west. Widespread MVFR is being observed across most terminals, with localized IFR/LIFR (including low VIS) near the convergence zone, and VFR conditions in the Northwest Interior. Models have the low clouds lifting roughly 18-20Z, with VFR conditions for the remainder of the afternoon and evening. Most areas will see southwest winds 5-10 kt, with a few gusts to 15-20 kt in the south sound, and 20-25 kt near the Strait of Juan de Fuca. Diffluence from winds in the strait will result in north winds from 22Z-06Z before turning back to the southwest. Medium chance again for MVFR ceilings Friday morning (may be more localized in nature). Winds also becoming breezy again from the southwest early Friday morning with gusts to 20 kt in the Puget Sound.

KSEA...MVFR ceilings to continue through roughly 18-20Z. Convergence zone will remain north of the terminal with showers through the morning. Lifting/scattering of ceilings to VFR takes place this afternoon through the evening. Medium chance of MVFR again Friday morning. Southwest winds in the morning 6-12 kt, will turn north briefly from 22Z through 06Z, returning to the southwest tonight/Friday morning. Potential for gusts to 20 kt this morning and Friday morning.

HPR

MARINE

Few showers continue behind a front that pushed through early this morning across the waters. The showers may reduce visibilities in isolated portions of the interior waters. Breezy winds with a push behind the front will continue to produce winds to 25 kt in the Strait of Juan de Fuca, where a small craft advisory continues through tonight. A ridge will offshore, making the onshore gradients relax and decreasing winds. A broad low moves in from the Gulf of Alaska Friday into the weekend, which will keep the flow onshore. Pushes through the strait will be much weaker, and at this time will not produce any impacts to mariners traversing the waters.

Seas remain 6-8 ft or less through the next seven days, but may approach 9 ft in pockets Monday and Tuesday.

HPR

FIRE WEATHER

Low level onshore flow today with temperatures near normal. Relative humidity values will stay well above critical thresholds. Cool unsettled weather Friday and Saturday. Thunderstorm chances elevated Saturday afternoon for the entire area. Lightning will be a primary hazard, and depending on the moisture accompanying each thunderstorm, may pose a risk to drier areas of grasses/cured fuels. Preceding cool conditions (and live fuels still growing and in the green up phase) will limit holdover risk as temperatures remain cool early next week. Felton

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 11 PM PDT this evening for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.