textproduct: Seattle/Tacoma

SYNOPSIS

A pair of weather systems will produce showers and unseasonably cool conditions across Western Washington on Friday and Saturday. Drier and gradually warmer conditions will develop early next week as a weak upper level ridge begins to rebuild into the region.

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/

The next in series of frontal systems will spread showers and breezy winds across Western Washington into tonight. A secondary, stronger system will quickly follow Friday afternoon into Friday night with a trailing upper trough settling over the area on Saturday. High temperatures both days will be as much as 10 to 13 degrees below normal. Along with the cool air mass will come some instability for isolated thunderstorm activity. The best probabilities for any storms will be on Saturday when the upper trough axis is overhead and a fairly potent convergence zone is likely to form Saturday afternoon. Snow levels will fall to 3500 to 4000 feet in the Cascades on Saturday. As of now, accumulation at pass levels looks rather minimal, but several inches could fall higher up at places like Paradise.

LONG TERM /SUNDAY THROUGH THURSDAY/

The upper trough axis will shift eastward on Sunday as low amplitude upper ridging slowly begins to build into the area. This should allow most of the area to dry out with temperatures trending upward a notch...though still a bit below normal. Heights continue to rise into Monday and Tuesday...though probably not enough to prevent a weak system passing to our north from clipping the region with some clouds and perhaps a couple showers across the North Interior and coast. Looking toward the middle of next week and beyond, ensemble height anomalies keep persistent upper troughing in place across the western Canadian provinces...which suggests that we'll struggle to get any upper ridging that lasts. It's still spring after all. Summer can wait.

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AVIATION

Westerly flow aloft throughout the night into Friday. A mix of VFR/MVFR this evening as showers stream onshore and likely at times throughout the remainder of the night. Southwesterly winds 10 to 15 knots will see some gusts up to 20 kts. Gusts will taper into Friday morning with sustained winds remaining elevated across much of the area.

KSEA...VFR and MVFR conditions have been observed so far this evening with occasional showers. Southwesterly winds 10 to 15 knots with occasional gusts up to 20 kts. VFR with MVFR cigs produced by showers will continue through the majority of the night, with winds tapering off early Friday morning but remaining around 8 to 12 knots.

Mazurkiewicz/41

MARINE

Onshore flow will continue over the weekend which will allow for daily pushes through the Strait of Juan De Fuca. Wind speeds are expected to largely remain below small craft criteria this evening, although some isolated gusts up to 21 kts can be possible at times this evening. Winds will increase over the coastal waters Saturday into Sunday along with a stronger push down the Strait that may warrant headlines.

Coastal seas 4 to 6 feet for much of today before rising to 7 to 9 feet tonight. Seas will then increase further on Saturday, rising from 9 to 11 feet lasting throughout Sunday.

Mazurkiewicz

HYDROLOGY

The daily hydrology discussion has ended until the start of the next rainy season; it will only be updated during this time as needed.

SEW WATCHES/WARNINGS/ADVISORIES

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