000 FXUS66 KSEW 241608 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 905 AM PDT Mon Sep 24 2018 .SYNOPSIS...An offshore upper level ridge will produce sunny, warm days and cool, clear nights through Saturday. Northerly low level flow will become offshore Thursday into Friday. The offshore ridge will slowly weaken late in the week with a weather system moving into the area Sunday. && .SHORT TERM...The areas of stratus and fog that formed overnight will clear this morning to sunny skies. The offshore upper level ridge will slowly shift inside of 140W this afternoon and evening which will help boost heights over Western Washington. At low levels, pressure gradients will become more northerly later today and linger into Tuesday which will help keep high temperatures in the mid to near 70 today despite the rising upper level heights and sunny skies. Skies will remain mostly clear tonight, with light winds so that areas of valley fog will once again form Tuesday morning, especially in the Southwest Interior. Lows Tuesday morning will be chilly again, in the upper 30s to near 50. Morning fog will once again burn off quickly Tuesday morning, to sunny skies with highs on Tuesday warming a bit over Monday`s highs into the mid 70s at some locations. Tuesday night and Wednesday will much the same - light northerly winds, chilly overnight temperatures, morning fog giving way to sunny skies and normal to above normal high temperatures. .LONG TERM...from previous discussion...Extended models continue to be inconsistent in their solutions. There is some general agreement with the upper level ridge gaining amplitude Thursday and Friday with the ridge drifting west. Both the GFS and ECMWF on the 00z run turn the surface gradients offshore Thursday and Friday. This solution has come and gone in the models for the last few days but with some consensus this morning have increased the high temperatures a little for Thursday and Friday even with the 500 mb heights falling in response to the westward movement of the ridge. Highs Thursday and Friday remaining in the mid 60s to mid 70s. If the offshore flow gets strong enough the warmest locations will be along the coast. Ridge continuing to drift west and north over the weekend with an upper level trough digging south along the British Columbia coastline arriving in Western Washington Saturday night or Sunday. Some timing and intensity differences this far out in the model run. At this point have added pops to Saturday night and increased the pops on Sunday but still kept them in the chance category. Temperatures will be cooler over the weekend with highs back down into 60s. Felton && .AVIATION...Northwest flow aloft continues today as high pressure offshore builds into the region. At the surface, flow will turn more northerly. Patchy stratus will dissipate this morning with VFR conditions expected across the area today. Less cloud coverage expected Tuesday morning but may see a brief period of IFR/LIFR again at KOLM and across portions of the southwest interior. KSEA...VFR conditions expected through the period. Light and variable winds this morning will turn northerly after 18Z, increasing to 7 to 10kts this afternoon. CEO && .MARINE...Northerly flow will prevail this week with high pressure in control. Winds will be breezy over the coastal waters but will likely remain below small craft advisory. Onshore flow may return by the weekend. CEO && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$ www.weather.gov/seattle
NWS SEW Office Area Forecast Discussion
Discussion Script by Ken True at Saratoga Weather - WFO Script by SE Lincoln Weather
