textproduct: Seattle/Tacoma

SYNOPSIS

A weak frontal system will move across Western Washington today producing little more than some cloud cover. High pressure aloft will rebuild into the area on Saturday for the return of some sunshine and somewhat warmer temperatures. Another weak system will clip the area on Sunday for additional clouds and a little cooling. High pressure will rebound once again early next week for a warming trend.

SHORT TERM /TODAY THROUGH SUNDAY/

A weak upper trough will swing inland across Western Washington this morning spreading clouds across the area, but little to no precipitation. The trough will be east of the Cascades by late this afternoon with some sunshine returning for most areas. With onshore flow in place, high temperatures will be similar to those of yesterday. Upper ridging rebuilds into the region tonight into early Saturday with the low level flow turning northerly. With the bump in heights and absence of onshore flow, high temperatures will climb a handful of degrees. Another system will clip the area on Sunday for additional cloud cover and perhaps a brief shower up across the Olympic Peninsula and North Interior. In typical fashion, NBM temperatures used in the forecast are underestimating the amount of cooling. Look for 5 to 7 degrees of cooling on Sunday...especially in the interior.

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/

Upper level ridging will amplify over the Pacific Northwest early next week in response to an upper trough that will dig southward well offshore. By Tuesday, 850 millibar temperatures climb to around 15C, but the low level flow stays weakly onshore which will keep temperatures in check...mid or upper 70s in the warmest spots.

Ensemble solutions begin to sow some considerable uncertainty into the forecast by the middle portion of the coming week as they, perhaps unsurprisingly, have trouble resolving what ultimately becomes of a closed off upper low west of north/central California. They're split between bringing a portion of it onshore or leaving it to aimlessly wander offshore. Either way, the main impact will be on temperatures with the precipitation outlook remaining particularly drier than what we'd expect in the first half of May.

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AVIATION

Westerly to southwesterly flow aloft as an upper level ridge moves over western Washington. VFR at all terminals early this morning with some mid to high level clouds around. Ceilings may lower to 4000 to 5000 across the area, but will expect to remain VFR, the exception being KHQM and areas along the coast where localized MVFR conditions can be possible throughout the morning. Elsewhere, VFR will remain throughout the day with SW winds generally 10 to 15 knots.

KSEA...VFR conditions with high clouds around. Ceilings may lower this morning to 5000 feet but will remain VFR. Southwesterly winds increasing to 10 to 15 knots, with speeds decreasing around 20-22z.

Mazurkiewicz

MARINE

Light onshore flow continues over the waters with a surface high pressure offshore. A weak front will cross over the area waters over this weekend for an increase in onshore flow. Small Craft Advisory strength winds are possible throughout the Strait of Juan De Fuca during the afternoon and evening hours Saturday and 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.