FXUS66 KSEW 290452 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 852 PM PST Sat Jan 28 2023 .SYNOPSIS...Cooler and drier air continues to filter southward into the region in the wake of a cold front that dropped across the area this morning. Strong high pressure over British Columbia will lead to Fraser River outflow winds through tonight. A warm front will develop and lift north into the area with the potential for a light rain and snow mix Tuesday into Wednesday. A more organized frontal system looks to impact the area later in the week. && .SHORT TERM /TODAY THROUGH TUESDAY/...Only minor tweaks made to the forecast this evening to account for latest radar trends. A frontal system draped across western Washington has continued to produce showers across the region, with KATX currently showing showers extending from Port Ludlow southward across the central Sound. Showers this evening continue to retrograde from the Sound westward towards the Olympic Peninsula. Have received reports of small hail, graupel, snow, and a rain/snow mix in heavier shower activity. As such, quick bursts of lowland snow will be possible through tonight in any heavier showers as snow levels continue to fall towards the surface. Drier air will filter into the region overnight into Sunday, so expect showers to taper within the next few hours. Otherwise, a cold night is on tap with cloud cover clearing across the area and with overnight lows expected to dip into the 20s. The remainder of the previous discussion follows below, with updates made to the aviation and marine sections. 14 A cold night is in store thanks to the clearing skies with lows dropping into the mid to upper 20s. It will stay somewhat breezy tonight, especially for area prone to Cascadia Gap winds and Fraser outflow. The Wind Advisory goes into effect for Whatcom, Skagit, and San Juan Counties from 6 PM through 6 AM where wind gusts to 50 mph are possible. A colder day is in store for Sunday with highs in the mid to upper 30s as the front and storm track sit well to our south. The good news is that it will be sunny with the only cloud cover being confined to the Cascades and Olympics. Another cold night Sunday night with lows dropping into the low to mid 20s thanks to clear skies. Lighter winds than tonight may allow for lows to drop even more in localized areas. Monday starts out clear with cloud cover rolling back in for the afternoon and evening as a warm front moves eastward toward the region. Highs will favor the upper 30s to around 40. Tuesday remains somewhat tricky as the mid-level ridge axis flattens out and shifts to our south and east as a weak impulse dives around the crest of the ridge. At the surface, a warm front will develop somewhere over the region. These two features will be the focus for the next round of precipitation. Ensemble guidance is still very much split over how robust this area of precipitation will be along the weak warm frontal boundary. Operationally, the CMC is the most aggressive with precip, with up to a half of an inch of snow in Seattle. The GFS and ECMWF operational keep the precip north of our area, however. .LONG TERM /WEDNESDAY THROUGH FRIDAY/...Chances continue for lowland snow into Wednesday. A handful of members of the EPS, GEFS, and GEPS bring a few tenths of an inch of snow into Seattle but only about 30% of the grand ensemble members bring measurable snowfall of at least a tenth of an inch into the Seattle metro through Wednesday afternoon. The EPS and GEFS have noticeably backed off on snowfall chances with fewer members now bringing measurable snowfall into the lowlands. Any snow that does fall will be extremely light with less than 10% of the grand ensemble members bringing an inch or more of snow into Seattle. With surface temperatures in the low to mid 30s both Tuesday and Wednesday afternoons, accumulation is not expected on roadways and would remain mostly confined to grassy and well-shaded surfaces, melting during each afternoon. A changeover to light rain is likely Wednesday afternoon as the front lifts north of the area and surface temperatures warm into the low to mid 40s. Winds will turn southerly as well into the afternoon. As we head into the latter half of the week, a break in precipitation may occur for the better part of Thursday as the warm front lifts into Canada and the main low and cold front lag to our west. Considerable timing differences exist in when the front moves through the area, but general agreement brings it through Thursday night. The pattern then looks wet into the weekend with several additional shortwave troughs spinning out of the larger longwave trough over the northern Pacific. Highs look to favor the upper 40s around 50 Thursday into the weekend. Davis && .AVIATION...Ceilings have recovered to VFR this evening, with skies expected to be mostly clear through Sunday. The only exception to this is an area of rain/snow/graupel around Puget Sound affecting KSEA and KBFI (and potentially KOLM) this evening. This activity should weaken and diminish in the next 1-2 hours as the frontal boundary associated with it continues south and weakens. But within this area of precip, the potential for temporary MVFR ceilings will exist. Winds will remain out of the N/NE through sunday, generally 8- 12kts through the overnight with a few gusts near 20kts (BLI likely to be gustier around 25-30kts) becoming 5-10kts Sunday late morning and afternoon. .KSEA...A short period of rain/snow/graupel through about 04-05z this evening with temporary MVFR cigs possible. Otherwise mostly clear and VFR. Winds N/NE thru the period 5-10kts with a few gusts near 20kts possible thru midnight. Kovacik && .MARINE...Fraser outflow/NE winds will continue tonight as a modified arctic frontal boundary pushes south across the area. As of 8PM, gale force winds were noted across the Northern Inland Waters and the Central Strait, with high end SCA level winds across the West and East entrances of the Strait and into portions of the northern Coastal Waters. All current headlines will remain in place into Sunday morning, with wind speeds slowly easing during this timeframe. By late morning Sunday, expect winds to be much lighter across area waters, where they will then remain calm through most of the first half of next week. Another system will approach Tuesday and Wednesday, which could result in SCA headlines. Aside from this, expect a quiet week for marine weather, with swells also remaining well below 10ft. Kovacik && .HYDROLOGY...No river flooding is expected through the next seven days. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...Wind Advisory until 6 AM PST Sunday for San Juan County-Western Skagit County-Western Whatcom County. PZ...Gale Warning until 7 AM PST Sunday for Central U.S. Waters Strait Of Juan De Fuca-Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Northern Inland Waters Including The San Juan Islands-West Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory until 7 AM PST Sunday for Admiralty Inlet- 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-Puget Sound and Hood Canal. && $$