textproduct: Seattle/Tacoma

SYNOPSIS

A low pressure system will remain situated over the Pacific Northwest through the weekend, maintaining cooler temperatures and daily chances for light showers and isolated thunderstorms. Split flow is favored to develop early next week, bringing drier and slightly warmer conditions. Chances for additional rain increase towards the end of next week with the potential arrival of another trough.

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/

A low pressure system that brought fall-like conditions to western Washington will continue to influence the weather into the weekend, bringing daily chances for scattered showers and isolated thunderstorms. The storm system will continue to drift southwards today, maintaining chances for showers and thunderstorms area-wide today. Showers will continue to develop over the Cascades and southern interior through the afternoon, drifting northwestward. The low pressure system will continue to shift southward through the evening, putting an end to ongoing convection as the environment becomes more stable.

More of the same is expected on Friday as the upper low slowly shifts inland. By Saturday, the low shifts northward, advecting wrap-around moisture into the area, bringing more widespread chances for showers and isolated thunderstorms. Temperatures through the short-term will remain below normal, with highs in the upper 60s to low 70s each day.

LONG TERM /SUNDAY THROUGH THURSDAY/

Forecast confidence decreases into next week, with some models keeping the low pressure system over us into Monday while some bring weak ridging over the area. While coverage decreases Sunday and especially into Monday, continued shower and thunderstorm activity remains possible alongside cooler temperatures. Models come into better agreement by Tuesday with split flow developing aloft, which would allow conditions to warm up and dry out with morning fog and low stratus. However, uncertainty remains over how long that would last, with another wet weather system on track to enter the region by next weekend.

15

AVIATION

South to southeasterly flow as an upper level low continues to dig southward along western Washington's coast. Mostly VFR conditions this afternoon with some localized spots of MVFR ceilings due to lingering scattered showers. Latest model guidance continues to a suggest a 10-20% chance of a thunderstorm across the area later this afternoon. Generally, confidence is low of any thunderstorm impacting any terminal as instability remains low. Overall, widespread VFR should continue throughout the evening, can could see brief MVFR at times in shower activity. S/SW winds this afternoon 5 to 10 knots could go variable at times, and will lessen in speeds overnight. VFR will continue into Friday morning, with some guidance suggesting a 20-40% chance of low cloud/fog development across lower prone terminals.

KSEA...VFR conditions this afternoon. Scattered showers will continue through the evening, could see brief MVFR conditions in any shower that passes over the terminal. Additionally, thunderstorm chances continue to remain low across the area (15-20%), with low confidence in any impact to the terminal. Southwesterly winds this afternoon 5 to 10 knots, will start to turn more variable and light overnight. Will likely see a return to southerly winds by Friday morning. MVFR patchy fog may develop around the terminal early Fri morning (20-30%) for a brief moment, but otherwise, VFR will continue.

Mazurkiewicz

MARINE

No current advisories across the waters with winds and seas continuing to gradually subside. Seas remain around 8 to 10 ft early this afternoon over the coastal waters, but will gradually decay through Friday. Broad low pressure remains in place, with showers and a few thunderstorms remaining possible, which could bring isolated gusty outflow winds. Otherwise, northerly winds develop over the waters Saturday through the start of next week. A marginal westerly push through the Strait of Juan de Fuca around Monday looks to be the next potential period of advisory strength conditions. Seas over the coastal waters subside further Saturday and remain in the 3 to 5 ft range through the first half of next week.

SEW WATCHES/WARNINGS/ADVISORIES

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