textproduct: Seattle/Tacoma

SYNOPSIS

Upper level low along the Central Oregon coast this morning will hardly move through Saturday morning. The low will drift north over Western Washington Saturday afternoon and remain in the vicinity until moving east Sunday night into Monday morning. Dry northwesterly flow aloft later Monday into Tuesday. A weak system will brush the area Thursday.

SHORT TERM /TODAY THROUGH SUNDAY/

Satellite imagery shows upper level low along the Central Oregon coast early this morning. Showers spinning around the low moving off the Cascades into the lowlands of Skagit and Snohomish county. Doppler radar also indicating isolated showers over the south Puget Sound. Temperatures at 3 am/10Z under mostly cloudy skies were in the upper 40s to mid 50s.

So far so good with the model predictions for where the low would go the last 24 hours. Low not moving much in the next 24 hours staying over Western Oregon. Once this current batch of showers rotates through early this morning a little break in the activity for the remainder of the morning. Air mass becoming somewhat unstable in the afternoon with showers developing over the higher terrain. Light east southeasterly flow aloft will try and push the showers into the lowlands late this afternoon into the evening hours. Winds at 700 mb and 500 mb 10 knots or less will make it hard for the showers to get all the way to the Puget Sound. With the light flow aloft any convection that does form has the potential to produce at least a brief heavy downpour with the cells moving slowly. Shower activity drying up in the evening hours with mostly cloudy skies overnight. A little bit of sun today pushing highs in the 60s and lower 70s. Lows tonight in the mid 40s to mid 50s.

Low starts to drift north Saturday morning ending up over Western Washington Saturday afternoon. Like today, showers developing over the higher terrain by late morning will try and float down into the lowlands in the afternoon and early evening hours. Light flow aloft continuing with the low overhead making it most likely the convection over the Cascades only gets to the Cascade foothills with the activity over the Olympics not getting all the way to the ocean. Showers dissipating in the evening with partly cloudy skies into Sunday morning. Persistence a good forecast for the temperatures Saturday and Saturday night. Highs maybe a couple of degrees warmer than Friday.

Low weakening but remaining in the vicinity Sunday. Could still see a shower over the Cascades especially the South Cascades in the afternoon otherwise just partly cloudy skies. Highs in the upper 60s to mid 70s. Felton

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/

Model solutions have been in good agreement for a few runs that the low kicks out to the east Sunday night and Monday. Dry northwesterly flow aloft developing over the area Monday will continue into Tuesday. Western Washington in a lull Wednesday with a weak upper level low developing well to the southwest and a weak system starting to slide down the British Columbia coast. System brushing the area Thursday for a slight chance of showers. Temperatures near normal through the period with mostly sunny days and partly cloudy nights. Highs upper 60s to mid 70s. Lows in the upper 40s to mid 50s. Felton

AVIATION

Variable flow aloft this morning as upper level low moves very slowly over W WA. Surface winds at most terminals also light and variable with speeds less than 5 kts. This looks to persist for most terminals, although some could see a shift to southerly winds this morning with speeds remaining light. Direction will shift to west or northwesterly this afternoon. Terminals on the east side of the Sound will see winds turn again more northerly in the evening. Speeds for all terminals will increase some, generally ranging 4-8 kts to finish the TAF period.

Widespread VFR conditions this early morning, although isolated patches of MVFR to IFR conditions are present along the coast, over the islands and in the SW interior. Cigs may lower a little more this early morning, however nothing indicating that bases will dip into lower flight categories. VFR conditions expected to persist throughout the TAF period as cigs lift further in the afternoon.

KSEA...VFR conditions this early morning and are expected to persist as per above discussion. Models had suggested the prospect, albeit a minor one, of low clouds or fog in the 12-15Z time frame, but at this time, while there are FEW to SCT clouds around 2500, clouds at this level remain broken up enough to keep flight category persistent. Southerly winds this morning and early afternoon generally 4-8 kts becoming northwesterly mid-afternoon, then north to northeasterly tonight with similar speeds.

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MARINE

Marine forecast remains uneventful as winds and seas remain below any sort of headline criteria. Broad low pressure remains in place, with showers and a few thunderstorms possible again today, 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 currently 4 to 6 ft, expected to ease just a little more this afternoon, down to 3 to 5 kt...and will remain there through the first half of next week.

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SEW WATCHES/WARNINGS/ADVISORIES

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