555 FXUS66 KMFR 181000 AFDMFR Area Forecast Discussion National Weather Service Medford OR 300 AM PDT Mon Mar 18 2019 .DISCUSSION...18/00Z NAM/GFS/EC in. Clear skies prevail across the Medford CWA this morning, except for marine stratus surging up the coast. Easterly flow has developed along the south coast, so the stratus along the coast around Brookings has moved back offshore. Expect more of that south of Cape Blanco as the morning progresses. It will continue surging north along the coast north of Cape Blanco. It will be dry today and quite warm, likely the warmest day of the year so far over the inland areas. Highs will be 10 to 15 degrees above normal over the west side valleys, and around 10 degrees above normal along the coast and from the Cascades east. A long wave ridge is now rebuilding just off the coast, and this is what is inducing the low level easterly flow. It will continue to build today, and the high will bubble up into western Canada today. The upstream trough will then undercut the ridge tonight into Tuesday, marking the beginning of the end of this recent spate of dry weather. The first front associated with the trough will begin to affect the area Tuesday afternoon. This will likely be a "sacrificial front", which will dissipate as it moves into the dry air mass in place. Tuesday will be another warm and dry day, a few degrees cooler than Monday over the west side. The east side will be a few degrees warmer though. Southeast winds will pick up a bit as well, but they won't be strong. The big change will occur Tuesday night into Wednesday as the trough edges closer to the Medford CWA. It will be much cooler, and high temperatures will drop to near normal values across most of the CWA. The exception will be the east side. While it will be much cooler, highs will still be up to 5 degrees above normal. Light precipitation will overspread most of the area, with amounts diminishing as one moves northeast from northwest California into central Oregon. Snow levels will start off around 6000 feet, then drop to around 5000 feet by Wednesday night. Thus, snow impacts are not really expected for most of the passes. The trough will still be offshore Wednesday night, but it will weaken. Showers will still be around, but coverage will be less and amounts will be lighter. Long term discussion from the Sunday afternoon AFD...Thu 21 Mar through Sun night 24 Mar 2019. The mechanism that will bring rainfall to much of the area, an upper trough and jet dynamics, will be pushing out and away from the forecast area Thursday. Therefore, rain will be diminishing during the day Thursday. Thursday night should be dry as a brief period of ridging precedes the next front, due to arrive Friday. Models have consistently shown a 24 hour period of precipitation lasting from Friday morning through Saturday morning. A well-defined front will bring snow levels down from about 6000 feet Friday morning to about 4000 feet Saturday morning. The latest data suggest 6 to 12 inches of snow in the Cascades and Siskiyous above about 5000 feet. The heaviest snow will be over Northern California due to upsloping, deep southerly flow. For rainfall, we expect a quarter to half inch in West Side valleys, about an inch of rain at the coast and in Siskiyou County, and a tenth to quarter inch of rainfall then changing to snow east of the Cascades Saturday morning. Additionally, a tightening pressure gradient east of the Cascades will probably result in breezy winds there Friday and Saturday afternoons. Conditions will begin to dry out on Sunday. Longer-term data, including most GEFS members, show continued cool and relatively active weather next week with near to below normal temperatures. && .AVIATION...For the 18/06Z TAFS...With generally offshore/easterly winds dominating the general pattern, VFR conditions are expected to prevail for inland areas throughout the TAF period. Areas of MVFR/IFR vsbys and IFR/LIFR cigs are occurring along the southern Coast near Brookings tonight, and will expand north along the coast tonight. IFR conditions are likely to make it north to Bandon, at least, but may push farther north towards KOTH. Some fog is also possible for the inland coastal valleys, namely in the Coquille and possibly, the lower Umpqua basins. Conditions are expected to clear to VFR along the coast Monday afternoon. -CC && .MARINE...Updated 200 AM PDT Monday 18 March 2019...Relatively calm conditions are expected for most of the week. It won't be towards the end of the week before we have to deal with any marine hazards. The thermal trough has expanded north along the coast which has allowed marine stratus to move north along the coast. This will continue into the morning hours. Winds will remain light through this afternoon. Winds turn south to southeast tonight into Tuesday, but conditions still don't look like they will quite reach advisory level. A gradual transition period for the coastal waters begins Tuesday, marked by building long period westerly swell. Seas will approach but not meet small craft advisory criteria Tuesday and Wednesday, but bar conditions may be on the rougher side due to the longer period component. There's better agreement among the models showing a more active pattern developing by Friday. A frontal system will approach the area Friday morning, bringing the potential for gusty south winds and steep seas. Friday afternoon through Saturday, the models are in pretty good agreement showing an increasing long period westerly swell of over 15 feet moving into the area Friday afternoon through Friday night. West swell will gradually decrease Saturday night and diminish below 10 feet Sunday afternoon. -Petrucelli && .MFR WATCHES/WARNINGS/ADVISORIES... OR...None. CA...None. Pacific Coastal Waters...None. $$ 15/15/10