textproduct: Seattle/Tacoma

SYNOPSIS

Cool upper level trough over Western Washington keeping the weather unsettled this morning. Rain out ahead of the next system reaching the area this afternoon with rain in the lowlands and snow in the mountains through Wednesday. Strong cold front moving through late Wednesday afternoon/Wednesday evening bringing blizzard conditions to the mountains and windy conditions to the lowlands. Atmospheric river taking aim at Western Washington beginning Thursday. The river will sag south late Friday night or Saturday morning. Upper level ridge building offshore Sunday and Monday with a warm front moving over the top of the ridge.

SHORT TERM /TODAY THROUGH THURSDAY/

Change in the forecast this morning. Blizzard warning has been pushed back to Wednesday night. Heavy snow in the mountains still on the way.

Busy morning. Lots to talk about. Satellite imagery and doppler radar shows convergence zone over Snohomish and Southeast Skagit county. Across the remainder of the area just some isolated showers west of Puget Sound. Temperatures at 3 am/10z were in the 30s.

Upper level trough remaining over Western Washington today. Temperatures are cold enough this morning for lowland snow showers but there is limited moisture. Best chances for snow showers this morning will be in the dissipating convergence zone and in the western portion of Clallam county. Increasing clouds for the remainder of the area. Upper level shortwave approaching from the northwest later this morning with rain out ahead of the shortwave spreading over Western Washington this afternoon. In addition to the rain it will be a breezy day with wind gusts in the 30 mph range common in the afternoon. High remaining cool, in the mid 40s.

Shortwave moving through tonight followed quickly by another system Wednesday spreading rain back over the area. Western Washington still on the cool side of the jet with snow levels remaining below the passes. New snow totals in the Cascades from this morning through Wednesday afternoon in the one to two foot range. Lows tonight in the mid 30s to lower 40s. Highs Wednesday near 50.

Sharp cold front moving through early Wednesday evening producing a variety of impactful weather. In the mountains model 850 mb winds in the 40 to 55 knot range just ahead, with and behind the front. This will produce blizzard conditions in the passes into early Thursday morning with another foot plus of new snow by sunrise. Along the coast strong post frontal westerlies with wind gusts as high as 55 mph. A wind advisory has been issued. Strong push through the Strait of Juan de Fuca as well. It's possible a wind advisory will be needed for the Admiralty Inlet area and Whidbey Island. Windy conditions for the remainder of the interior with wind gusts in the 30-40 mph range. Rain turning to showers behind the front. Lows near 40.

Little in the way of a break in the weather Thursday as an atmospheric river takes aim at Western Washington while the some cool for atmospheric river conditions air is still in place over Western Washington. Snow levels around 3000 feet with heavy snow likely in the Olympics and the Cascades. A winter storm watch remains in effect for the mountains beginning Thursday. In the lowlands another round of rain. Highs in the mid 40s. Felton

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/

Extended models in good agreement with the atmospheric river remaining over Western Washington until at least Friday night. Winter storm watch for the mountains remains in effect through Friday night. There is a good chance the mountains will see another two to three feet of snow between Thursday and Friday night. Upper level ridge building offshore pinching the river off and pushing it south later Friday night into Saturday. Possible break Sunday but right now more of the ensemble solutions pointing towards another atmospheric river getting over the top of the upper level ridge offshore moving into Western Washington Sunday night and Monday. Felton

AVIATION

Westerly - zonal flow aloft throughout the TAF period. A convergence zone is maintaining MVFR cigs for Puget Sound terminals (KSEA, KBFI, KPAE). This feature will continue before petering out around 14-16z then VFR should rebound. Elsewhere VFR cigs are present and will maintain before deteriorating towards 21z-00z as rainfall increase across W WA. MVFR to IFR cigs overnight into Wednesday morning as well. Surface winds are forecast to increase this afternoon with southerly gusts up to 20-30 kt for area terminals except for KCLM.

KSEA...MVFR cigs due to lingering PSCZ over the area. This feature will maintain before petering out towards 14-16z. Then VFR cigs should rebound before MVFR cigs redevelop (afternoon-early evening) and continue into early Wednesday as rain increases across W WA. Southerly gusts increase around 18-20z around 20-25 kt and remain elevated into the evening.

McMillian

MARINE

Onshore flow has eased into the morning but conditions are slated to remain active. Pre-frontal southerly winds will pick up this morning as SCAs have been issued for Puget Sound, Admiralty Inlet, East Strait and Northern Inland waters for today. SCAs for the coastal waters and Grays Harbor bar remain in effect as well due to winds and seas. A much stronger disturbance is on tap to arrive on Wednesday with the potential for widespread gale force winds. A brief window of storm force gusts are also possible as hi-res guidance is showing a 30-50% chance of them occuring over the Central and Eastern Strait on Wednesday evening. A weaker system will stall over the region Thursday and Friday. The flow will turn northerly on Saturday, then offshore on Sunday as a warm front moves into southern B.C.

Seas 8-12 ft today before rising to 10-15 ft Wednesday night. Seas then fall below 10 ft by Thursday afternoon and remain thereafter.

McMillian

HYDROLOGY

Moderate to heavy precipitation over the Olympics will cause the Skokomish River in Mason County to rise today with flooding possible beginning Wednesday. The river will remain high through the end of the week. Flooding is also possible on the Chehalis river from Grand Mound to Grays Harbor, Newaukum River and Skookumchuck River near Bucoda beginning Thursday. Crests on these rivers will occur Friday into the weekend. Several other rivers from Snohomish county southward are forecast to reach Action Stage later this week. The lower snow levels with the atmospheric river Thursday through Friday will make river forecasting tough during this event. After a short break it is possible another atmospheric river will move over the area early next week. With the already high running rivers ahead of the event this will be closely watched for another round of possible river flooding. Felton

SEW WATCHES/WARNINGS/ADVISORIES

WA...Winter Weather Advisory until 6 PM PDT Wednesday for Cascades of Snohomish and Northern King Counties-Cascades of Whatcom and Skagit Counties.

Blizzard Warning from 6 PM Wednesday to 5 AM PDT Thursday for Cascades of Pierce and Lewis Counties-Cascades of Snohomish and Northern King Counties-Cascades of Southern King County-Cascades of Whatcom and Skagit Counties- Olympics.

Winter Storm Watch from late Wednesday night through late Friday night for Cascades of Pierce and Lewis Counties- Cascades of Snohomish and Northern King Counties-Cascades of Southern King County-Cascades of Whatcom and Skagit Counties-Olympics.

Winter Weather Advisory until 6 PM PDT Wednesday for Cascades of Pierce and Lewis Counties-Cascades of Southern King County.

Winter Weather Advisory until 11 AM PDT this morning for Foothills and Valleys of Snohomish and Northern King Counties-Lake Crescent Area Including US 101-Western Strait of Juan de Fuca.

Flood Watch from Wednesday afternoon through Thursday afternoon for Foothills of the Western and Southern Olympic Peninsula-Middle Chehalis River Valley-Olympia and Southern Puget Sound-Olympics-Southern Hood Canal- Willapa and Black Hills.

PZ...Small Craft Advisory until 5 PM PDT this afternoon for Grays Harbor Bar.

Gale Watch from Wednesday afternoon through late Wednesday night for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca-West Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 10 AM this morning to 8 PM PDT this evening for Admiralty Inlet-East Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland Waters Including The San Juan Islands.

Small Craft Advisory from 10 AM this morning to 11 PM PDT this evening for Puget Sound and Hood Canal.

Small Craft Advisory until 2 PM PDT Wednesday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm- Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.

Gale Watch from Wednesday afternoon through Wednesday evening for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.