textproduct: Seattle/Tacoma

UPDATE

Satellite imagery shows low cloud deck hanging tough over portions of the area this morning. Stratus isn't very deep with tops below 2000 feet. Low level flow is light which will make it hard to get rid of the cloud cover. In addition to the light flow in the lower levels high clouds moving through this morning will also hinder the breaking up of the low cloud deck. Current forecasts have a late afternoon break out and that looks good at this point. With the cloud cover hanging on highs a touch warm in the forecast with mid to upper 50s instead of lower 60s. Previous discussion follows with updated aviation section. Felton

SYNOPSIS

Onshore flow will increase tonight and Monday for showers and a convergence zone. The next system will bring additional lowland rain, windy conditions plus possible heavy mountain snow on Tuesday. Upper level low over western Washington Wednesday for continued cool conditions. Drying northerly flow aloft developing Thursday into the weekend.

SHORT TERM /TODAY THROUGH TUESDAY/

A brief break in the weather this morning and early afternoon as an upper level low shifts inland to our south (over northern CA). Showers will then increase late this afternoon and evening, primarily over the interior and Cascades, as low level onshore flow increases. Onshore flow continues into Monday with convergence zone showers over King/Snohomish counties.

Cool, wet and windy conditions are ahead as we move into Tuesday while a deep upper low descends south from B.C. Snow levels will lower to around 3000 ft with snow expected at all Cascade passes. Winds will be gusty from the S/SW with gusts to 25-35 mph (peaking in the interior during the afternoon). 33

LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/

Wet and cool conditions will continue Tuesday night and Wednesday as a deep upper low spins over WA. Snow levels will lower further, down to around 1500-2000 ft, with snow in the Cascades and passes. Mean 48 hour snow totals range from 6 to 12" inches with higher amounts on the volcanoes. Expect cooler lowland temperatures with lows in the 30s and highs in the 40s to around 50.

Drier weather is in store Thursday into the weekend with high pressure. Lows remain chilly and in the 30s with freezing temperatures around the south sound. Expect highs in the 50s with lower 60s by Saturday. 33

AVIATION

Variable to northerly winds aloft as a weak trough sets up over western Washington. Fog and low clouds have brought IFR to LIFR cigs/vis but conditions are beginning to gradually improve. VFR is slated to return by 20-22z. Winds will remain northerly throughout the afternoon but will keep speeds generally 3 to 6 knots. MVFR/IFR cigs are like to redevelop this evening for Puget Sound terminals as a convergence zone develops.

KSEA...LIFR conditions have lifted to IFR so far this morning as fog and low clouds developed earlier at the terminal. Northerly winds generally around 3 to 6 knots and remaining there throughout the afternoon. Latest guidance shows a 60-70% chance of conditions returning to VFR by 18z-20z as fog/low clouds start to dissipate. Winds will start to turn more SW by 20z and increase slightly to 4 to 8 knots. MVFR/IFR cigs are to return this evening as a convergence zone develops.

Mazurkiewicz/McMillian

MARINE

Surface low pressure continuing to move southward as a high pressure system develops offshore in the northeastern Pacific. Generally calm and benign northerly winds over the waters this afternoon. A small craft advisory remains in effect for increased westerlies down the Strait of Juan de Fuca late Sunday into Monday. A stronger frontal system arriving late Tuesday into Wednesday will likely yield additional headlines as we will see increased winds and seas.

Coastal seas 4 to 6 feet throughout the weekend. Seas will then start to build upwards to 8 to 10 feet by Tuesday evening and remaining elevated through Thursday.

Mazurkiewicz

HYDROLOGY

No river flooding the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory from 5 PM this afternoon to 11 AM PDT Monday for Central U.S. Waters Strait Of Juan De Fuca- East Entrance U.S. Waters Strait Of Juan De Fuca.