538 FXUS66 KMFR 221755 AFDMFR Area Forecast Discussion National Weather Service Medford OR 955 AM PST Sat Jan 22 2022 .Updated Aviation Discussion. .AVIATION...22/18Z TAFs...VFR conditions prevail over the entire area except for MVFR conditions due to low clouds over the Umpqua Basin, including Roseburg, northward into the Willamette Valley, and the north end of the Rogue Valley, including Medford and Grants Pass. Guidance suggest Medford could break out between 20-21z, however given the fog layer is shallow, conditions could improve an hour earlier than whats indicated in the TAF. Meanwhile, it's likely to take longer for Roseburg to clear out, if they do at all, but there should be enough drying aloft that should mix down near the surface later in the afternoon allowing Roseburg to clear out. VFR conditions are expected this evening and most of the night, but expect low clouds and fog again between 11-12z for similar locations as this morning. -Petrucelli .DISCUSSION...22/12Z NAM in. 22/12Z GFS in through 42hr. Mostly clear skies prevail over the Medford forecast area this morning, except for low clouds and fog over the west side valleys and some scattered high clouds. The low clouds will clear later this morning into this afternoon, lingering the longest over the Umpqua. The northern hemispheric pattern shows a progressive 5 wave pattern around the globe. That is usually progressive, but all that is getting trumped by a block over the eastern Pacific that is sort of a combined rex/omega block. Dry north to northeast flow aloft is in place over the west coast. The ridge will weaken through the weekend, and flow aloft will become northwest Sunday into Monday, but the ridging will continue to dominate the weather pattern over the area. So, it will be dry. The valleys will see night into morning low clouds and fog with cold nights and mild afternoons under the inversion. The ridges will see some variation, as low level easterly flow will continue into Sunday with the northeast flow aloft. This will make for overall mild conditions there under mostly clear skies. RH recoveries will gradually worsen, but that won't be much of a concern this time of year. Onshore flow will return Sunday into Monday. Marine stratus will return to the coastal waters and coast in that time frame, cooling down those areas. The primary near term issue in terms of impacts is air stagnation in the valleys. At this point, it does not look like stagnation will be an issue today. However, it will be an issue through the coming week, and an Air Stagnation Advisory for valley locations is in effect beginning tonight and running at least through Friday night. The pattern will become progressive again beginning Tuesday, but it will be a very slow progression. The ridge axis will finally move onshore Wednesday. Flow aloft will become southwesterly. This will open the storm door, but the operational EC and GFS solutions differ significantly as to what will happen next. The EC pushes a trough and its associated front onshore Friday into Friday night, while the GFS depicts zonal flow aloft with continued dry conditions. The current forecast, based on the NBM, shows the next chance of precipitation over the area will be Friday at the earliest. Even then, the chances are less than 30 percent. The 8 to 14 day outlook, valid from 29 January to 04 Feb, calls for below normal temperatures, along with near normal precipitation west of the Cascades, and above normal precipitation from the Cascades east. && .MARINE...Updated 800 AM PST Saturday 22 January 2022...Moderate north winds will gradually decrease during the day. Lighter winds are expected late afternoon through Sunday night, but a longer period swell will also build on Sunday. Another round of gusty north winds and Small Craft Advisory conditions is possible by Monday night when the thermal trough redevelops. -Sven/Petrucelli && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Air Stagnation Advisory from 10 PM this evening to 4 AM PST Saturday for ORZ023>026-029>031. CA...Air Stagnation Advisory from 10 PM this evening to 4 AM PST Saturday for CAZ080>082-084-085. Pacific Coastal Waters... Small Craft Advisory until 7 PM PST this evening for PZZ370-376. $$ 15/10/10