Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
094 FXUS66 KSEW 190957 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 257 AM PDT Wed Jun 19 2024 .SYNOPSIS...High pressure aloft will gradually build through the week, allowing conditions to dry out and warm up. A pattern change is on track for the weekend as a trough brings wetter and cooler conditions to western Washington. && .SHORT TERM /TODAY THROUGH FRIDAY/...Mostly clear skies in place over W WA this early morning as the area finds itself more under the influence of an upper level high over BC as opposed to the weak troughiness to the south. As this high remains fairly stationary for the remainder of the work week, dry conditions will persist with warming temperatures through Friday. Daytime highs today will get into the mid to upper 70s for most of the interior lowlands while the coast and most water adjacent areas will see highs in the mid 60s to right around 70. Surface level high pressure over southern BC will set up an offshore flow pattern Thursday, further boosting temperatures in what will be the warmest day all around with most lowlands seeing highs in the mid 70s to lower 80s. Start seeing hints of the return to onshore flow starting Friday, as coastal and water adjacent locations return to the mid 60s to around 70 while the interior remains toasty with highs once again in the mid 70s to lower 80s. While the majority of the CWA will be dry, it is worth mentioning that some lingering moisture and instability over the Cascades...particularly the North Cascades, will still run the risk for some afternoon and evening scattered showers and possibly some isolated thunderstorms. Rainfall with any of these showers or thunderstorms is expected to be generally light. Lastly, this discussion of warming temperatures once again turns attention to heat risk potential. Even with the high temperatures mentioned above, overnight lows will continue to cool down into the lower to mid 50s throughout the area. While there are pockets of moderate HeatRisk...mainly confined to the Seattle metro area and some of the Cascade valleys, current data suggests widespread heat impacts are expected to be minimal at this time. 18 .LONG TERM /SATURDAY THROUGH TUESDAY/...An incoming frontal system associated with an upper level low dipping south from the Canadian coast hints at a little bit of a pattern change for the weekend and the beginning of next week as the low mostly sits and churns in place, pushing at least a couple of fronts through the area. This will take a degree or two off daytime highs Saturday but will knock temps back into the 60s for most locations Sunday and Monday...with some recovery back to the lower 70s Tuesday. PoPs during this time frame are less than impressive however, with most of the CWA only seeing chances ranging from the single digits to around 20-30 pct Monday morning. Instead, the coast and northern tier of the CWA appear to be favored, where PoPs there will peak in the 40 to 50 pct range both Sunday and Monday. Tuesday sees activity starting to wind up...but PoPs will still linger in the 10-20 pct range for the aforementioned favored locations. 18 && .AVIATION...Weak upper level trough over Western Washington into Thursday morning with light flow aloft. Surface high pressure centered off British Columbia with northwesterly surface gradients. Clear skies over Western Washington into Thursday with patchy fog/low clouds along the coast 12z-15z. KSEA...Clear skies. Northeast wind 6 to 10 knots becoming northwesterly around 21z. Winds switching back to northeasterly after 06z. Felton && .MARINE...High pressure centered off British Columbia today will move south tonight and Thursday with weak onshore flow. Onshore gradients increasing later Friday with surface high pressure over the coastal waters ahead of weak system arriving over the weekend. Gale force westerlies possible in the Central and Eastern Strait of Juan de Fuca Friday night with small craft advisory winds in the adjacent waters. Small craft advisory westerly winds in the Strait Saturday evening. Felton && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$