Point Grenville to Cape Shoalwater WA out 10 NM Marine Forecast
|Today...Nw Wind 15 To 25 Kt Becoming W 5 To 15 Kt In The Afternoon. Wind Waves 2 To 4 Ft. W Swell 11 Ft At 12 Seconds. A Chance Of Rain In The Morning Then Showers And A Slight Chance Of Tstms In The Afternoon.|
|Tonight...Nw Wind 10 To 20 Kt. Wind Waves 1 To 3 Ft. Nw Swell 11 Ft At 11 Seconds. Showers And A Slight Chance Of Tstms.|
|Mon...N Wind 5 To 15 Kt Rising To 15 To 25 Kt In The Afternoon. Wind Waves 2 To 4 Ft. W Swell 10 Ft At 11 Seconds. A Chance Of Showers In The Morning.|
|Mon Night...Ne Wind 15 To 25 Kt Becoming E 10 To 20 Kt After Midnight. Wind Waves 2 To 4 Ft. W Swell 9 Ft At 13 Seconds.|
|Tue...Se Wind To 10 Kt Rising To 15 To 25 Kt In The Afternoon. Wind Waves 1 To 2 Ft Building To 2 To 4 Ft In The Afternoon. W Swell 7 Ft At 13 Seconds.|
|Tue Night...S Wind 20 To 30 Kt Rising To 25 To 35 Kt After Midnight. Combined Seas 7 To 10 Ft With A Dominant Period Of 15 Seconds.|
|Wed...Sw Wind 15 To 25 Kt Easing To 5 To 15 Kt. Wind Waves 2 To 4 Ft Subsiding To 1 To 2 Ft. W Swell 10 Ft Building To 12 Ft.|
|Thu...E Wind To 10 Kt. Wind Waves 1 To 2 Ft. W Swell 10 Ft Subsiding To 7 Ft.|
| Area Forecast Discussion|
National Weather Service Seattle WA
832pm PST Sat Nov 26 2022
No changes to the current forecast this evening. A robust upper level low is currently pushing across northern BC, with associated cyclonic flow extending from the Gulf of Alaska, along the BC Coast, and into Washington. Several embedded shortwaves are noted within the broader cyclonic flow, to the west of main area of closed low pressure. Near the surface, a cold front extends southwestward from a cyclone centered just downstream from the upper level parent low over northern BC, while high pressure encompasses much of the western US.
Stratiform rain is spreading into W WA this evening, associated with an approaching shortwave trough and the aforementioned cold front. Most of the rain currently resides over the Olympic Peninsula and across the Cascades, with Puget Sound and areas around the Northern Inland Waters rain-shadowed. Overnight tonight, expect breezy conditions area-wide, but particularly across the north interior (around Bellingham and Mt Vernon), the San Juan Islands, and the North Coast. Heavy mountain snow is also expected with snow levels remaining below Stevens Pass through the night and below Snoqualmie Pass early Sunday morning. This system will be fast-moving, with most of the stratiform rain exiting between 15-18z Sunday. Showery conditions will then persist through the day within an unstable environment as mid level temps fall to around -30 to -35C, yielding the potential for an isolated lightning strike and brief heavy downpours.
Previous discussion follows with an updated marine and aviation section.
/issued 339pm PST Sat Nov 26 2022/
Active weather is expected through much of next week. A strong front will begin to impact the area tonight bringing with it lowland rain, mountain snow and gusty winds. Convective showers will linger into Monday with the potential for isolated thunderstorms. An upper level trough moving into the area will result in colder temperatures and the potential for lowland snow.
Short Term - Tonight Through Tuesday
The next frontal system will begin impacting the area this evening and will continue into Monday. This frontal system will bring heavy mountain snow, gusty winds, lowland rain and the chance of some isolated thunderstorms. Specific details regarding the aforementioned weather impacts is as follows.
Snow levels between 3000-3500 feet will be quickly dropping during the overnight reaching 1000-1500 feet by Sunday morning. The bulk of the snow will be associated with the frontal passage on Sunday, but with persistent post frontal showers as well as the convergence zone will add to accumulations particularly over the Central Cascades. In total 1-2 feet are are expected between now and Monday at both Snoqualmie and Stevens Pass. With Stevens Pass likely experiencing the higher accumulations. Those traveling over the pass should check the forecast as well as road conditions before heading out as travel will likely be difficult.
Mountain snow will taper throughout Monday morning. There is the chance of flurries into Tuesday evening, but no significant accumulation is expected until late Tuesday.
This frontal system will bring gusty south winds to the north coast and north interior tonight with south winds 30-40 MPH with gusts to 55 MPH. Winds will ease early Sunday morning except for the Admiralty Inlet area where gusty west winds will continue (through mid morning) due to a strong westerly push down the strait.
Persistent widespread lowland rain is expected tonight as a front moves through the area. Rain will become more scattered and showery throughout the day Sunday and into Monday. With leaves still lingering in the area there could be some localized ponding of water is expected in the urban areas due to clogged storm drains. Exercise caution while traveling through the large puddles.
Lowland precipitation type becomes a bit of a question mark for some areas Sunday night into Monday morning. With snow levels around 500 feet and lows in the upper 20s to low 30s there is the potential for any of the remaining showers to be in the form of snow. Most lowland areas should not see any accumulation, but there are always a few exceptions. The first being in the I-5 corridor from Mount Vernon northward and the second being along US 101 from Quilcene to the west side of Crescent Lake. These two areas could see trace to a few tenths of an inch of snow accumulation Sunday night to Monday morning, but there is high uncertainty with this potential. Snow in these areas is going to be very dependent on where the lingering showers remain as well as how quickly low level winds shift to northerly.
Showers will dissipate throughout the day Monday creating a brief period of drier weather into Tuesday. As an upper level trough deepens over the area temperatures and snow levels will continue to drop, and with the next system expected to be moving through Tuesday there will be a chance of some lowland snow. Right now accumulations are not looking likely on Tuesday as the precipitation will likely begin late morning, when temperatures are expected to have warmed up to the upper 30s to low 40s. But certainly a rain/snow mix is possible, particularly under areas of heavier precipitation and north of Seattle. There is still a good amount of uncertainty with this as it is going to be very dependent on the timing of the precipitation, low level winds and temperatures.
There is a decent amount (for this area) of instability behind the front that will be moving through the area tonight and into Sunday. The higher amounts of instability are offshore/at the coast as well as in the general PSCZ area. With the instability and the colder temperatures there could be enough ice within the scattered showers to charge the atmosphere enough for some isolated thunderstorms to occur Sunday afternoon and evening. Any thunderstorms that do form will be short lived.
Long Term - Wednesday Through Saturday
The upper level trough that was discussed in the short term will continue to impact the Western Washington area through the remainder of the forecast period. The overall consensus from all the ensembles is that it will be colder, snow levels will be low, and there is a good chance for the first lowland snow event of the season. Where the ensembles as well as their respective members begin to differ is the amount of lowland snow. The system moving through Wednesday is likely going to be the main producer of widespread precipitation. How much of this precipitation is in the form of snow is really going to depend on the placement of the upper level trough. Ensembles have been keeping the trend of the east side of the trough just off shore, this would keep most of W WA in the southwesterly flow and slightly warmer conditions. However, the trough placement is a bit precarious as any shift eastward or it strengthening would keep us well within the northerly flow that would be needed for a widespread lowland snow event.
The greatest chance of >1" of snow along the I-5 corridor will be from Tacoma to the Canadian boarder. Confidence in this ranges from 50-70% with confidence increasing as you head north.
After the Wednesday system moves through the area will remain unsettled. Showers will continue to linger in the area and multiple disturbances will be moving through. With temperatures in the 20s-30s any precipitation that does occur could be in the form of snow.
AVIATION...Rain will continue to spread across the area tonight, eventually exiting the area by mid-morning Sunday with showers following in the wake. Most TAF sites are reporting MVFR (Marginal Visual Flight Rules) and IFR this evening, and do not expect much deviation from current conditions through the night and into tomorrow morning. Vsbys likely to be reduced as the bulk of the rain pushes through each site. Conditions will try to improve to VFR Sunday afternoon but will struggle and may remain higher-end MVFR. Winds will be breezy out of the S/SW tonight 10-15kts with gusts 20-30kts. Breezy W/SW winds continue through the day Sunday 8-12kts.
KSEA...MVFR (Marginal Visual Flight Rules) conditions through early Sunday morning with rain through most of the overnight period. An improvement to low-end VFR late Sunday morning and afternoon is possible with showers in the vicinity. Winds breezy out of the S/SW thru the period 10-15kts, with gusts tonight 20-30kts.
South to southwest winds starting to increase in Puget Sound and expected to spread over majority of inland waters tonight, remaining in place through Sunday morning thanks to a passing frontal system. Inherited headlines look good with Gales in most waters and an SCA (Small Craft Advisory) up for the Sound...although the latter will need to be watched as the 7pm PST ob from West Point came in just under gale. While no other observation in the Puget waters shows that kind of speed, if the next ob comes in higher, a short fused upgrade may be in order. Strongest winds still expected to be over the northern Coastal Waters and the Strait of Juan de Fuca. Meanwhile, seas will also build to around 10-14 feet as a swell train reaches the coast tonight. Winds will ease behind this system Sunday afternoon. Winds will turn offshore and strengthen on Monday with gusty Fraser River outflow winds expected over the Northern Inland Waters. Another strong Pacific frontal system will arrive Tuesday or Tuesday night, keeping the pattern active. 33/18
No river flooding expected over the next 7 days.
NOAA Seattle WA Office: Watches - Warnings - Advisories
WA...Wind Advisory until 6am PST Sunday for North Coast-San Juan County-Western Skagit County-Western Whatcom County.
Wind Advisory until 9am PST Sunday for Admiralty Inlet Area.
Winter Storm Warning until 7am PST Sunday for West Slopes North Cascades and Passes.
Winter Storm Warning until 10am PST Monday for West Slopes North Central Cascades and Passes-West Slopes South Central Cascades and Passes.
PZ...Small Craft Advisory from 4am Sunday to 4pm PST Monday for
Grays Harbor Bar
Gale Warning until 4am PST Sunday 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-
West Entrance USA Waters Strait Of Juan De Fuca.
Gale Warning until 6am PST Sunday for
Central U.S. Waters Strait Of Juan De Fuca-
East Entrance U.S. Waters Strait Of Juan De Fuca-
Northern Inland Waters Including The San Juan Islands.
Small Craft Advisory until 4am PST Sunday for
Puget Sound and Hood Canal