textproduct: Seattle/Tacoma

SYNOPSIS

A broad upper trough will remain over the area well into next week with a series of low pressure systems maintaining below normal temperatures and periodic chances of showers.

SHORT TERM /TODAY THROUGH MONDAY/

A convergence zone continues to affect Snohomish and Skagit counties early this morning. This is expected to diminish toward dawn as low level onshore flow begins to relax somewhat. A closed upper level low will gradually shift southward across Western Washington today with the focus for shower activity shifting to higher terrain of the central/south Cascades and portions of the Southwest Interior. Some areas around Puget Sound might catch a few peeks of sun this afternoon, but temperatures will remain a little below normal.

Models are latching on to a compact closed upper low slipping southward along the coast on Sunday. This system doesn't look like it will produce much of any precip, but it will ensure that we see plenty of cloud cover with temperatures continuing their recent trend of several degrees below normal for the end of June. Broad upper level ridging centered well offshore attempts to briefly nose into the area on Monday, but continued onshore flow and meager height recoveries point toward mostly cloudy and cool conditions persisting.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

Strong upper level ridging centered well offshore around 150W and over the eastern half of the lower 48 will keep a mean upper trough position anchored over the West Coast through much of the extended forecast period. This keeps the door open for additional upper level systems to dip southward from British Columbia maintaining below normal temperatures and producing periodic chances for showers.

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AVIATION

Scattered shower activity is being observed along the coast, over the Cascades, and the north Puget Sound, associated with a PSCZ. The PSCZ continues to bring IFR/MVFR conditions and intermittent showers to KPAE. Expect the PCSZ to wind down around 15Z as a cold upper- level low will slides southeastward into western Washington Saturday morning. This will bring a renewed threat for showers across western Washington late Saturday morning through the afternoon. The best chances (50-80%) will be in the mountains with a 30-50% chance around Puget Sound terminals. This also comes with a 15-25% chance for thunderstorms. The highest confidence for thunderstorms will be primarily for the southern Puget Sound (Thurston County, western Pierce County) and Lewis County where the cooler temperatures aloft associated with the center of the upper-level low supports taller storms. A mix of MVFR and VFR conditions are expected through the period with MVFR conditions favored through 17-18Z before improving to VFR. Winds will be out of the south 6-10 kts this morning and gradually shift to the west through the late morning and then to the west-northwest this afternoon.

KSEA...VFR ceilings currently being observed with a 50% chance for MVFR ceilings between 13-17Z. There is high confidence for VFR conditions to return after 17Z and remain VFR through the evening. Probabilities for ceilings below 2000 feet increase to 50-80% after 09Z Sunday. There is a slight chance (15%) for thunder Saturday afternoon, but confidence is not high enough to include it in the TAF. Southerly winds 5-9 knots will shift to the southwest around 17Z and then to the west-northwest around 00Z-05/06Z before shifting back to the south-southwest. /vmt

MARINE

The overall pattern over the next several days will feature a broad surface ridge centered well offshore with lower pressure across the interior promoting onshore flow. This will lead to gusty northwesterlies over the outer coastal waters and the development of steep, choppy seas later today and into early next week. In addition, the central and east Strait of Juan de Fuca will likely see diurnally driven increases in westerlies reaching small craft advisory strength on a routine basis. The offshore ridge is expected to weaken toward late next week allowing for lighter winds and subsiding seas.

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FIRE WEATHER

Little in the way of fire weather concerns remain in the picture well into the week ahead with upper troughing maintaining cool conditions, high RH, and periodic chances for shower activity.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory from 5 PM this afternoon to 2 AM PDT Sunday for Central U.S. Waters Strait Of Juan De Fuca- East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 2 PM this afternoon to 5 PM PDT Sunday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm.