FXUS66 KSEW 152221 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 321 PM PDT Fri Oct 15 2021 .SYNOPSIS...Deep Pacific moisture coupled with a stationary cold front just offshore will bring continued rainfall to the northern half of the area into Saturday. This front will start to work its way inland late Saturday and into Sunday allowing for more widespread precipitation and locally breezy conditions. A brief break is expected Monday before active weather resumes for much of next week. && .SHORT TERM /TONIGHT THROUGH MONDAY/...Northern portions of the CWA still seeing rainfall as per latest radar imagery with not much variation on where the rain is falling, still generally north of a line running from northern Grays Harbor county to the King/Snohomish county border. Southern portions remain dry thanks to upper level ridging just south of the area. Not much in the way of change is expected tonight and during the overnight period as the AR remains pointed north of the area, primarily focused on western British Columbia. Pre-frontal winds will pick up over the area Saturday, mainly impacting the usual spots prone to higher wind speeds /coast and north interior/. Forecast remains on track that wind speeds here will remain below advisory criteria, so breezy to locally windy wording should be just fine. In terms of weather, not much change expected between Friday and Saturday, with rain continuing over the northern half of the CWA while the southern half will remain generally dry. A strengthening upper level ridge over the Great Plains will reorient the AR to run parallel with the cold front along the coast, severing it from its source of tropical moisture. This front will move inland starting late Saturday night and it will spend of the bulk of Sunday slowly plodding eastward. Current model solutions have slowed the feature down, turning it into an all day thing before gradually tapering off Sunday evening. Snow levels during this event expected to remain high...above 6000 ft...so not expecting much in the way of snow in the mountains as the front moves through. The front should exit the area by Monday morning with an upper level ridge bringing a break in precipitation over the area and perhaps even some peeks of sun. Afternoon high temps during this period will warm a little bit with lower to mid 60s Saturday before cooling with the front down into the mid to upper 50s Sunday and Monday. 18 .LONG TERM /TUESDAY THROUGH FRIDAY/...While the upper level ridge exits the area by Tuesday morning, the effects linger as W WA remains on the backside keeping conditions dry through much of Tuesday. Deterministic models differ in timing as to when the next system will move in...either late Tuesday night or Wednesday morning...while ensembles seem to point more toward the latter option. Some uncertainty with how successful and how far east this system will be, depending on a continuing ridge over the Central US. NBM is leaning a little on the wetter side...which is what is present in the forecast...but given the wide variety in ensemble members, cannot say it stirs up much in the way of confidence. It is this Central US ridge that ends up shaking confidence in the remainder of the forecast period as deterministic models and ensemble members all paint an active pattern right along the Pacific Coast...but the westward impacts of said ridge will be vital in determining whether or not any of these systems will have an impact on W WA for the second half of next week. Practically every ensemble member and each deterministic model has a different solution as to how far east precip reaches into the area. This again allows for the NBM to lean a little more on the wet side of things, however, given the high degree of uncertainty, who can say whether or not this might be accurate. At the very least, it provides future shifts with a starting point to make alterations should a consensus emerge. 18 && .AVIATION...A frontal system will continue to give the northwest portion of Washington rain but areas south of Everett should be mostly dry. The air is moist and stable. Southwest flow aloft. The mountains and foothills will be obscured and the lowlands will have MVFR conditions with local IFR cigs. 19 KSEA...Cloudy drippy weather with a southerly breeze will continue. && .MARINE...Blustery at times in the normally windier locations like the coast and northern waters as a very slow frontal system is draped over the area. This frontal system will keep southerly gradients over the areas through Saturday morning before the front finally moves ashore Saturday afternoon and evening--although westerlies behind the front probably do not arrive until Sunday. Weak high pressure finally shifts over the area on Monday. Another front should reach the area next Wednesday. 19 && .HYDROLOGY...Heavy precipitation is expected along a frontal boundary that will remain rather stationary over the 24-36 hours, impacting areas in particular along the North Coast and Western Whatcom County and North Cascades. Continuous rainfall is expected beginning this morning, continuing through Sunday. Overall rainfall amounts may range from 4-6 inches along the North Coast to 2-4 inches over portions of Western Whatcom County and the North Cascades. Rivers in these areas are expected to rise over the next several days, but currently no river flooding is expected. Kovacik && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory until 5 PM PDT Saturday for 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 U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory until 10 PM PDT Saturday for Grays Harbor Bar. Gale Warning until 5 PM PDT Saturday for Admiralty Inlet-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-East Entrance U.S. Waters Strait Of Juan De Fuca- Northern Inland Waters Including The San Juan Islands. Small Craft Advisory until 11 AM PDT Saturday for Puget Sound and Hood Canal. && $$ www.weather.gov/seattle