Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
895 FXUS66 KSEW 111052 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 352 AM PDT Sat May 11 2024 .SYNOPSIS...Upper level ridge over the area today will weaken tonight and Sunday. Upper level trough moving through Sunday night with a weak upper level disturbance Monday. Another upper level ridge moves through Western Washington Tuesday. Possible unsettled weather Wednesday into Friday. && .SHORT TERM /TODAY THROUGH MONDAY/...What a show! That had to be the best aurora visible in the Seattle earlier this morning. Satellite imagery shows clear skies over Western Washington. Surface gradients have gone flat with light winds being reporting in most locations. Temperatures at 3 am/10z are mostly in the upper 40s and 50s with Seattle and Everett still in the lower 60s. Upper level ridge over the area today starting to weaken this afternoon. Surface gradients remain light this morning before becoming onshore this afternoon. The transition to onshore flow will result in much cooler temperatures along the coast with highs mostly in the 60s. Interior high temperatures a little tougher to forecast. Temperatures aloft cooling slightly with the weakening ridge. Onshore flow in the afternoon will put the breaks on the daytime heating but temperatures this morning are 3 to 6 degrees warmer than yesterday. End result is high temperatures near what they were on Friday with just a couple of degrees of cooling, 70s to lower 80s. Upper level ridge continuing to weaken tonight with increasing onshore flow. Stratus along the coast spreading inland but still looks like most of the stratus will stay west of Puget Sound. Lows tonight in the upper 40s to mid 50s. Upper level trough offshore approaching the coast but remaining offshore Sunday. Low level onshore flow continuing throughout the day giving the interior a good 10 to 15 degrees of cooling. Highs along the coast will be in the lower to mid 60s. For the interior mid 60s to lower 70s. Upper level trough moving through Sunday night. Weak upper level shortwave embedded in the northwesterly flow aloft arriving Monday. Not much in the way of dynamics with both of these features. The shortwave could set off some light showers in the Cascades Monday. Lows Sunday night in the upper 40s to mid 50s. Highs continuing to cool over the interior with upper 50s to mid 60s forecast for the entire area. .LONG TERM /TUESDAY THROUGH FRIDAY/...Models in good agreement for Tuesday with a brief upper level ridge rebuilding over the area for a dry and slightly warmer day. Once again confidence is low for Wednesday through Friday with the models very inconsistent in their solutions. The operational ECMWF brings a weak front into the area Wednesday followed by an upper level trough Thursday that moves out of the area Friday. The operational GFS has an upper level ridge over Western Washington Wednesday weakening Thursday with an upper level trough arriving Friday. The GFS ensembles are dry through the period while the ECMWF ensembles have about half of the solutions being wet from Wednesday night through Friday. Forecast for now is a broadbrush mostly cloudy with a slight chance of showers Wednesday night through Friday with high temperatures trending slightly above normal. Felton && .AVIATION...An upper ridge remains in control with westerly flow aloft. The air mass is dry and stable. Low level onshore flow will increase today as thermally induced low pressure shifts into the interior of Western Washington. This will bring IFR ceilings in stratus to coastal areas tonight, but VFR conditions will prevail elsewhere. KSEA...VFR. Surface winds light and variable wind becoming W/NW less than 10 knots this afternoon and evening. 27 && .MARINE...Thermally induced low pressure shifts into the interior of Western Washington today then east of the Cascades tonight and Sunday. This will lead to increasing onshore flow. A weak system will pass to the north of the area Sunday night and Monday. Small craft advisory conditions will develop over the coastal waters today and continue through the weekend. A westerly push in the strait will develop later today, but a stronger push on Sunday could produce gales in the central/east strait. Onshore flow will prevail through much of early next week for periodic small craft advisory winds across the coastal waters as well as the strait. 27 && .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. && $$