textproduct: Seattle/Tacoma

SYNOPSIS

A progressive pattern will prevail across the area through the rest of the week as several back-to-back systems bring rounds of precipitation and gusty winds. The system late tonight into Thursday looks to be the wettest. A brief break between systems will be possible Saturday before another systems arrives on Sunday. A warming and drying trend returns next week as high pressure rebuilds.

SHORT TERM /TODAY THROUGH FRIDAY/

Satellite imagery show a cold front traversing across western Washington this morning. Radar shows scattered showers moving northeastward across the area, however, not a ton of this is making it to the ground, as there is a dry near-surface layer that is evaporating some of the rain. The heaviest showers are producing a few hundredths of an inch in the lowlands, with a few tenths in the Olympics where the upslope regime is helping to squeeze out some more rain. At the passes, temperatures remain below freezing with vertical profile indicating snowfall being the primary precipitation type. Winds have peaked and will ease early this morning, but remain in the 20-30 mph range for much of today.

This front will work its way across the area early this morning, but the warm front from the next system will already be on its tail. Precipitation chances will increase this afternoon along the coast, moving inland this evening. Winds will also increase late tonight as the cold front moves through the area early Thursday. Winds look to peak in the 30-40 mph range for most, but some localized gusts up to 45 mph will be possible along the coast and around Whidbey/San Juan Islands. Rain and winds will slowly taper off throughout the day Thursday.

Temperatures will begin to warm and snow levels will begin to rise above pass level this afternoon. Additionally, easing easterly pressure gradients will allow winds to ease and limit the amount of cold air coming in from the east. This will allow for a clean transition from snow to rain at the passes this afternoon. Snow levels will remain above pass level, reaching the 5000-6000 ft range Thursday and remain like so.

Precipitation totals with this system will be in the 0.25-0.5" range through the interior lowlands, with higher amounts along the Pacific coast and the Olympics where upslope flow will be favored (1-3", locally up to 4"+). This will bring the potential for localized flooding impacts in this area. See HYDROLOGY below for additional details.

Again, another system will be on the heels of the previous system, with renewed, albeit lesser, precipitation chances late Thursday into Friday, as well as locally gusty winds.

On the Pacific coast, large waves will arrive along the coast late tonight into Thursday, where waves up to 18-20 ft will bring high surf conditions.

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/

The system arriving late Thursday will depart late Friday. There is good consensus that there will be enough distance and time in between the next two systems that there will be a break in the rain on Saturday, which will be supported by an amplifying upper level ridge. This will also allow temperatures to spike a bit, reaching the mid to upper 50s. The next system will move through Sunday into Monday, returning to cool, wet, and breezy conditions. Models are beginning to show the potential to returning to a large ridging/omega blocking pattern, which would allow for more warm/dry conditions as systems get pushed well north into B.C. and Alaska. There remains a few ensemble members with wet solutions into next week (due to a lower-amplified ridge), but the vast majority favor the former.

The threat for coastal flooding will also return this weekend into early next week as we reach new moon on Feb 1. At this time, the weather does not look to significantly exacerbate impacts, with only minor impacts currently expected primarily for sensitive areas in the Puget Sound and Salish Sea. The coastal flooding threat will continue to be evaluated and refined throughout the week.

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AVIATION

Upper level troughing over the region will maintain southwesterly flow aloft through the TAF period. Showers will continue across the region early this morning as a frontal system pushes inland. Conditions across the area terminals primarily remain VFR this morning, with the exception of KHQM, where conditions have already lowered to MVFR. The next round of more widespread rain will move into the coastal terminals between 16-19Z and into the interior terminals between 19-21Z. Expect ceilings to gradually lower towards more widespread MVFR throughout the day as a result and remain predominantly MVFR into Thursday. Winds persisting out the SE primarily between 7-12 kt could be breezy at times through the morning hours. Winds will increase later this afternoon and evening, with gusts to 20-30 kt possible at times. The strongest winds will occur for terminals along the Pacific Coast (KHQM) and across the North Interior (KBLI), where localized gusts to 35-40 kt will be possible tonight into early Thursday.

KSEA...Showers at times with VFR conditions at the terminal this morning. Expect ceilings to lower to MVFR by this afternoon as the next round of more widespread rain moves into the terminal between 19-21Z. SE winds will persist between 7-12 kt, but could be gusty to 20-25 kt at times through the day. An uptick in winds is expected again tonight into Thursday with the next system, where gusts to 25-30 kt will be possible. 14

MARINE

A frontal system currently pushing inland is bringing gusty winds to the interior waters early this morning. This system will continue to bring gales to the eastern Strait of Juan de Fuca through the early morning hours. Overall, expect winds to ease in the wake of the front this morning, but expect winds to remain breezy, with most area waters (outside of the central and western Strait) still expected to see gusty small craft southerlies through much of the day. Seas across the coastal waters will generally range between 10-14 ft through the day.

Another frontal system will then move across the area waters tonight into Thursday, bringing another round of southerly gales to the coastal waters and the eastern Strait. The extent of gales will need to be monitored and may need to be expanded northward to the Northern Inland Waters as well, with latest guidance currently indicating a 50-60 percent chance of gales developing across the majority of the zone. Elsewhere, outside of the central and western Strait, expect southerly winds to increase again and persist between 20-30 kt into Thursday morning. Seas will build to 15-20 ft across the coastal waters late tonight into Thursday.

An active and progressive pattern will continue over the next several days, with additional systems expected to move across the area waters on Friday and again over the weekend. These systems will likely bring additional headlines to the area waters at times. Seas hovering between 12-16 ft on Friday will subside heading into the weekend and will generally range between 9-12 ft heading into early next week.

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HYDROLOGY

A series of systems will move across western Washington over the next several days, bringing multiple rounds of precipitation to the area. Rainfall totals will be most pronounced on the Olympic Peninsula, especially along the south slopes of the Olympics- where 1 to 3 inches of rain, with localized spots of 4 inches, will be possible. This, in addition to snow levels rising to 6000-7000 feet, will cause rises on the Skokomish River. At this time, the river could reach flood stage as early as Thursday morning and looks to remain above flood stage into Saturday. While rises will occur on other area rivers, river flooding is not expected on the remainder of the area rivers.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...Flood Watch from 4 AM PST early this morning through late Friday night 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 4 PM PST this afternoon for Grays Harbor Bar.

Small Craft Advisory until 6 AM PST early this morning for Admiralty Inlet-Northern Inland Waters Including The San Juan Islands-Puget Sound and Hood Canal-West Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Warning until 6 AM PST early this morning 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-East Entrance U.S. Waters Strait Of Juan De Fuca.