546 FXUS66 KSEW 162215 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 315 PM PDT Sun Oct 16 2022 .SYNOPSIS...An upper-level ridge axis will shift east tonight and into Monday. A surge of marine cooled air will surge into western Washington bringing a noticeable cool down during this time but temps are likely to remain above average. Ridging persist through much of the week before a trough enters on Friday night. Here we'll see our best shot of wetting rain since early June and actual fall-like temperatures. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY/...Today has been a historic day across the region in terms of high temperatures. At the time of this writing, Sea-Tac is at 84F which not only shatters the daily record high but this would be the highest recorded temperature this late in a calendar year (records go back to 1945). Taking into account of the old Federal Building statistics in Seattle proper (records go back to 1894), its record of highest recorded temperature this late in a calendar year has also fallen as it is currently 83F here at the WFO. To note though, Sea-Tac is the official climate site for the area. Focusing on the forecast, the upper-level ridge axis will track eastward tonight into Monday. A surge of marine cooled air is slated to push into the interior, bringing increased cloud coverage and cooler temperatures. However, we'll still be well above average for mid-October with daytime highs in the upper 60s to low 70s. If there's a silver lining wildfire smoke looks to usher out briefly on Monday due to the return of onshore flow. But, gradients look to turn offshore again Tuesday night into Wednesday which could bring additional smoke but coverage and density won't compare to this past weekend's conditions. The upper-level pattern shows the ridge retrograding back over the area on Wednesday. Conditions are slated to remain dry and unseasonably warm during this time. Similar day to day temperatures are expected for both Tuesday and Wednesday as well. Highs in the 60s to low 70s with lows in the 40s to near 50. .LONG TERM /THURSDAY THROUGH SUNDAY/...Upper-level ridging shows signs of weakening ahead of a trough arriving on Friday. It's associated front will bring our best shot of rainfall across the region since early June of this year. Likelihood is increasing on the rainfall potential as nearly all of the ECMWF ensembles are indicating rainfall. GFS ensembles are also trending towards the ECMWF's solution, further increasing forecaster confidence. Showers could linger through the rest of the weekend. This disturbance will not only bring rainfall but much cooler temperatures, possibly returning us to seasonal values. Highs could be near 60 on Friday and remain in the 50s on through Sunday. McMillian && .AVIATION...Upper level high pressure will shift slightly east this evening, allowing for southerly flow aloft. Offshore flow in the low levels is also subsiding, with E/NE winds shifting W/SW this afternoon and evening at 5-10kts. This will help improve vsbys as smoke is pushed eastward. Given the better onshore flow, marine stratus will expand eastward overnight/early Monday, likely bringing LIFR-IFR ceilings to most of the TAF sites. Recovery to VFR expected by the afternoon, except perhaps HQM where stratus will linger in close proximity. KSEA...A wind shift to the W (6-8kts) this afternoon will reinforce vsby improvements into Monday. VFR conditions through most of the overnight may give way to a brief period of LIFR-IFR ceilings Monday morning for a few hours. Marine stratus will lift by the afternoon, with clear skies/VFR conditions prevailing thru the rest of the TAF period. Kovacik && .MARINE...Offshore flow continues near the surface this afternoon as a thermal trough lingers between the Coast and Puget Sound while high pressure continues east of the Cascade Crest. This continues to make for an N/NE wind component across the waters, with the exception being the central and southern coastal waters where southerly flow (along with marine stratus) has already been established. Offshore flow will subside this evening, with winds turning more west/southwesterly. A diurnal westerly push down the Strait is expected this evening, and given a substantial temperature gradient between the coast and interior lowlands, will need to monitor for gale force winds down the Strait. For now, have adjusted wind speeds upward a few knots, approaching higher-end SCA level criteria to reflect this potential. Elsewhere, isolated SCA level southerly winds will be possible over the outer coastal waters this evening as a weakening frontal boundary approaches, but do not feel it will be widespread enough to warrant a SCA. Better onshore flow will allow marine stratus to spread into the interior waters through Monday morning. This will help push smoke to the east, with improvements to visibility likely. Winds will be breezy out of the south on Monday over the waters, but will not be strong enough to reach criteria. Light offshore flow will then become reestablished Tuesday, with some marine stratus still possible and perhaps some smoke advection into the waters, but no impacts are currently expected. Big changes then potentially on the horizon as a more active pattern develops at the end of the week and next weekend. A robust frontal system is expected to cross the area Friday night and Saturday, which may bring widespread gales to area waters. Given some disagreement in model solutions, will reflect higher-end SCA level winds through this period, but this may very need to be adjusted upwards. Active weather may then continue beyond this event. Hazardous seas are also expected through this general period, possibly ranging from 10-12ft. Kovacik && .FIRE WEATHER...Critical fire weather conditions continue through late this afternoon with warm, dry and windy conditions across the west slopes of the Cascades. The current Red Flag Warning remains in effect. Onshore flow returns Monday for higher RHs and cooler temperatures. The air mass will remain dry Tuesday and Wednesday with min RH in the 20s and 30s once again in the Cascades. This critical dryness combined with a mid-level Haines of 6 near the crest will keep the fire danger threat elevated for dry and unstable conditions. A strong front will bring cooler and wetter conditions and more fall-like weather on Friday. 33 && .HYDROLOGY...The daily hydrology discussion has ended until the start of the next rainy season; it will only be updated as needed. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...Red Flag Warning until 5 PM PDT this afternoon for West Slopes of the Central Cascades Generally above 1500 Feet-West Slopes of the North Cascades Generally above 1500 Feet. PZ...Small Craft Advisory from 5 PM this afternoon to 2 AM PDT Monday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. && $$