textproduct: Seattle/Tacoma

SYNOPSIS

A weak system will brush the region today. The weather pattern becomes more active starting Wednesday as a series of systems brings lowland rain, high elevation snow, gusty winds, and the potential for high surf to western Washington. A brief break in the unsettled weather is possible Friday night into Saturday, before additional systems arrive late in the weekend into early next week.

SHORT TERM /TODAY THROUGH THURSDAY/

A weak system brushing the region will bring spotty light showers to western Washington through the morning hours, although not much in the way of rain will reach the surface due to continued drier conditions in the low levels. Conditions dry out by this afternoon as shower coverage decreases. Afternoon highs will be a few degrees warmer today than yesterday, with temperatures expected to top out in the mid 50s to low 60s. Clearing skies this evening and the reintroduction of some moisture in the low levels will bring back the potential for fog development across the area by early Wednesday. Overnight lows will be in the mid 30s to low 40s, with a few spots across the South Sound approaching freezing.

The weather pattern becomes more active starting Wednesday as the first in a series of systems moves across western Washington. This system will bring lowland rain, high elevation snow, and gusty winds to the area. More details on each hazard follows below:

Rain: The bulk of the moisture with this system will be focused over the Olympic Peninsula and the North Cascades. Rainfall amounts for the Pacific Coast are expected to range between a quarter of an inch to half an inch. Many spots across the interior lowlands will get rain shadowed, with only a few hundredths to a tenth of an inch of rain expected.

Mountain Snow: Snow levels generally be hovering between 5000- 6000 ft will bring a few inches of snow to the higher peaks of the Olympics and North Cascades. Most likely snow amounts across the higher terrain are between 1-3 inches, with some locally higher amounts possible near the higher peaks like Mt Baker.

Gusty Winds: Winds will increase as this system approaches the region, with southerly winds expected to pick up along the coast during the afternoon hours and increasing across the interior during the evening hours. Winds will be strongest along the Pacific Coast, where wind gusts between 25-35 mph will be possible. Areas across the interior will likely see wind gusts to 25 mph.

Winds will ease and precipitation will taper overnight into Thursday, which will bring a quick break in between systems. Afternoon highs on Thursday will be in the mid to upper 50s.

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/

A stronger system will move into western Washington Thursday night into Friday, bringing another round of gusty winds, lowland rain, high elevation snow, and the potential for high surf along the Pacific Coast. The bulk of the moisture with this system will again remain aimed at the Olympic Peninsula and the North/Central Cascades. Snow levels around 5000 ft will climb to 5500-7000 ft through the day on Friday and will support high elevation snow across the Olympics and Cascades, with 1-2 inches of rain expected in the lower mountain elevations. The highest rainfall amounts across the lowlands will be along the North Coast, where 1 to 2 inches of rain is expected into Saturday morning. Many areas across the interior lowlands will be rain shadowed again and generally look to receive a couple tenths of an inch of rain. Winds will become gusty as the system approaches, with probabilistic guidance indicating a 50% chance of wind gusts exceeding 40 mph along the Pacific Coast and a 40-50% chance of wind gusts exceeding 40 mph for areas from Whidbey Island northward. Increasing potential for high surf conditions developing along the Pacific coast could bring risks for beach erosion and hazardous conditions along beaches and jetties.

Ensemble clusters continue to hint at a brief break in the unsettled weather pattern early Saturday as a transient ridge of high pressure moves back over the region. Discrepancies remain in regards to the amplitude of the ridge at this time, however, it does look to aid in directing the bulk of the moisture of the next system further north into British Columbia. Even though the bulk of the moisture will be focused to the north of the border, the North Coast and the North Cascades could still be clipped by this system.

The ridge does look to move inland rather quickly which would open the door for a wet system to move into the area Saturday night into Sunday. The pattern will remain active heading into early next week as additional systems look to arrive into the region.

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AVIATION

A thick high cloud layer across the Pacific Northwest will keep most areas with VFR conditions through the majority of the TAF period. There remains some localized areas of fog this morning across portions of the South Sound, but should lift and mix out this morning. Radar shows some scattered showers but most of this won't make it to the ground. Cloud coverage decreases this evening/overnight, which will open up another window for fog or low stratus Wednesday morning. Best chances for said conditions to develop are from the Kitsap to the south interior from 12-15Z through 18-20Z. Winds will remain light out of the north/northeast around 5 kt. Winds will start to pick up Wednesday morning at the end of the TAF period as a frontal system beings to approach the area.

KSEA...VFR conditions expected for Tuesday with high clouds, clearing this evening. This will open up the potential for fog early Wednesday morning, with a 25-30% chc of low ceilings/fog btwn 13-17Z Wed. Winds remaining out of the north/northeast at around 5 kt.

HPR/62

MARINE

A stationary front remains offshore with a low pressure system passing by to the south into California. Seas remain around 8-11 ft at around 15 seconds over the coastal waters this morning. Seas will be slow to ease but should reach around 6-8 ft across the area tonight. The Small Craft Advisory will continue through this afternoon for the outer coastal waters. The weather then becomes more active with a series of systems moving through the region beginning mid week and continuing this weekend into early next week. The first frontal system moves through on Tuesday, with high likelihood (60-90% chc) for small craft winds over the coastal waters. Friday's system will be stronger, with both wind and sea concerns. Majority of the waters will hazardous winds for small craft. The inner coast and east Strait of Juan de Fuca have a 35% chance of gusts reaching gale force. Seas will build Thursday into Friday, peaking at 15 to 18 ft with another long period swell train. The Saturday/Sunday, and Monday/Tuesday systems has similar probabilities for small craft and gale gusts to the Friday system. Seas as a result will likely remain over 10 ft going into the weekend/early next week (12-15 ft).

HPR/62

HYDROLOGY

River flooding is not expected through the next seven days. However, a series of increasingly wet weather systems will bring rain (and high mountain snow) to the region this week, especially from Friday onward. While current forecasts are not expected to cause flooding, this will begin to saturate soils and raise base flows that could bring a concern with subsequent storms systems.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 4 PM PST this afternoon for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm- Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm.