Seattle Weather

232 AM PDT Friday may 9 2008

Corrected to add a sentence to the marine segment.

Synopsis: An upper level ridge will build into Western Washington today giving warmer and drier conditions. A weak cold front will pass through the area Saturday, followed by showers and cooler temperatures Sunday. Another break in the weather is expected on Monday. A warm front will brush through the area on Tuesday. Temperatures will gradually warm up Wednesday through Friday as a strong upper level ridge builds over the pacific northwest.

Short Term: Skies are mostly clear over the lowlands with a few more clouds over the higher terrain. provided we don`t End up with sunrise surprise status formation, we will end up with a mostly sunny day. With plenty of sunshine and limited flow we should be able to squeeze into the lower 60s many areas today.

A cold front will approach the region early Saturday and sort of ooze on across the area as it decays. Basically not a lot of upper level support for the front so it will be weak. Surface gradients will be fairly light but we will go from offshore flow in the morning to onshore later in the day. Precipitation will be fairly limited as well, especially over the interior where i changed the wording to light rain or sprinkles. Temperatures should end up in the mid 50s to around 60 despite the mostly cloudy skies as we will start the morning off fairly mild.

For the remainder of the weekend an upper level trough settles in over the pacific northwest for cooler temperatures and an enhanced threat of showers. Will keep the shower threat in the chance category through the daylight hours Sunday with threat diminishing Sunday night. Temperatures will be nearly 10 degrees cooler than normal Sunday with afternoon highs in the middle 50s. cerniglia

Long Term: Interesting developments, which by the middle of the week could mean either sunny and very warm or, occasional heavy rain especially over the olympics. trend has been (and still is) For a ridge to begin building over the west coast into early Wednesday. At our latitude there is enough moist flow through the building ridge that there remains a threat of light rain Tuesday everywhere and over northern areas Wednesday. Current forecast remains untouched this period as it looks good as is. This is where things potentially become interesting.

on one side we have the gfs solution(south) Which continue to build a strong ridge over the northwest for sunny and very warm conditions, at least until the marine push kicks in. This also supported rather well in the 00z gfs ensembles which have a rather tight grouping through 180 hours. This would normally build great confidence. however, the last few runs (12z Thursday and 00z last night) Of the ecmwf have begun hinting at a suppression of this ridge with a strong and very moist southwest flow across the eastern pacific into the northwest. This can be traced back to a typhoon that is currently in the far western pacific that gets captured in the westerly flow and directed our way. The hpc center mentioned that this scenario was the case in the ecmwf ensemble members as well. At another point they mentioned that the ecmwf ensembles have trumped the gfs ensembles this spring across the country. This will need to be watched. If this tropical system gets sucked up into the westerlies, it will likely end up as a rather narrow band of heavy rain directed somewhere at the northwest, likely at british columbia. Will leave forecast as is do to uncertainty this far out and see just how this tropical system tracks. cerniglia

Aviation: Vfr conditions are expected to prevail. Cigs should remain in the 3-5k ft range this morning. There may be some patchy fog, vsbys at or above 2sm, over the southwest interior or roughly from kolm to ktdo. Expect scattered clouds across the entire area by 20z.

At ksea, cigs should remain at or above 3k ft. The clouds will become scattered by 19z. Winds will be south or southwest 5-10 kt, becoming northwest later in the afternoon.

Marine, weak onshore flow will prevail through tonight. Meanwhile, a weak front over the Eastern Pacific will move across the coastal waters Saturday afternoon, and the inland waters Saturday evening. The timing of this front could end up a bit faster as shown in the forecast by the hydrometeorological prediction center. Expect increased onshore flow behind this front that will persist through Sunday.

sew watches/warnings/advisories, None.