Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
073 FXUS66 KSEW 112119 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 219 PM PDT Sat May 11 2024 .SYNOPSIS...Upper level ridging will start to weaken into Sunday, although still providing warm and dry conditions across western Washington. A weak system will move across the area Sunday night into Monday with a touch cooler temperatures. High pressure looks to build back into the area Tuesday into Thursday with warm conditions. Unsettled weather looks to make a return by the weekend. && .SHORT TERM /TONIGHT THROUGH TUESDAY/...Recent satellite imagery shows another beautiful day across western Washington. Upper level ridging will start to weaken over our area into Sunday, with high temperatures in the interior this afternoon topping out to generally around 80 degrees. The transition to onshore flow this afternoon will help the coastal locations cool down, with high temperatures there this afternoon to be in the low to mid 60s. As the upper level ridge weakens tonight, skies will remain mostly clear throughout most of the interior, with the possibility for some patchy stratus along the coast. It will be another good night for viewing conditions for the Aurora Borealis, especially for interior locations. Refer to spaceweather.gov for more space weather information, including tonight potential for viewing. The aforementioned ridge will start to move eastward on Sunday and flatten, weakening the thermal trough along the coast. This will likely lead to slightly cooler temperatures across the area tomorrow, along with increasing onshore flow, afternoon high temperatures can be expected to generally be around the low to mid 70s. A weak system will cross into our area Sunday night into Monday, bringing a chance of showers across most of the region, with the most likely areas to receive any precip would be the Olympics and the Cascades. Increased cloud cover on Monday will bring temps down to around normal, in the mid 60s. High pressure looks to rebuild back in the area on Tuesday, for slightly warmer temps in the low 70s for the interior, and mid 60s for the coast. .LONG TERM /WEDNESDAY THROUGH SATURDAY/...Ensemble guidance in good agreement for a high pressure to build through Wednesday for dry and warm conditions, with high temperatures not warming up too much, staying in the low to mid 70s. Confidence is still somewhat low looking at the end of next week, with the ECMWF ensemble highlighting and unsettled pattern Friday and into Saturday which would bring increased precipitation chances - meanwhile, the GFS ensemble decides it wants another weekend or dry and warm conditions over western Washington. Cluster analysis also favors the ECMWF solution a bit which would bring unsettled weather into next weekend, but nonetheless, temperatures look to remain around seasonal normals, but could change if ridging does develop. Mazurkiewicz && .AVIATION...An upper ridge remains in control with westerly flow aloft, but weakens today. Low level onshore flow will increase today as thermally induced low pressure shifts eastward, with a passing upper level disturbance allowing for the return of some IFR ceilings to return to the coastal areas. Not a sufficiently strong push to reach into much of the interior with continued VFR conditions under clear skies for most terminals. KSEA...Northerly winds around 7-9 kt through evening with VFR conditions under mostly clear skies. Any inland push of stratus likely too weak to bring much into to south Sound or closer to the terminal area - around than a 15% chance at best. Winds likely a bit variable as they go light overnight, but predominantly northwest winds expected Sunday once winds increase mid-morning onward. Cullen && .MARINE...Thermal low pressure located near the coast will shift onshore this afternoon before pushing east of the Cascades overnight, bringing an increase in onshore flow. The strongest winds (that is, most consistently around 20-25 kt) will remain over the outer coastal waters, but with frequent gusts to 25 kt over all of the coastal zones, as well as in the central and eastern Strait of Juan de Fuca, have maintained the existing advisories. Over the coastal waters, the seas will remain rather choppy and approaching if not meeting steepness criteria, as well, further supporting the maintaining of the advisories. Elsewhere, with a weak front dropping north of the area Sunday night and Monday, expect the onshore flow to further increase. Have upgraded the gale watch to a warning for the central and eastern Strait for late Sunday as a result. Additional frontal systems will continue to cross the waters through much of next week, with winds periodically building to near advisory thresholds. Meanwhile, seas over the coastal waters will build a bit with each passing system and remain generally short period, around 7 to 9 seconds, through the middle of next week. Cullen && .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...None. PZ...Small Craft Advisory from 4 PM this afternoon to 3 AM PDT Sunday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. Gale Watch from Sunday morning through Monday morning for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory from 5 PM this afternoon to 11 PM PDT Sunday for Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm. Small Craft Advisory until 3 AM PDT Monday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm- Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm. && $$