FXUS66 KPQR 040551 AFDPQR Area Forecast Discussion National Weather Service Portland OR 951 PM PST Tue Dec 3 2024 .SYNOPSIS...High pressure over the region will produce dry weather through at least Wednesday, with areas of clouds and fog in the interior valleys and sunshine elsewhere. Rain chances start to increase Thursday/Friday into the weekend with snow levels remaining above the Cascade passes through Saturday. && .DISCUSSION...Little change in the overall pattern as high pressure persists over the region this morning. Satellite imagery and surface observations from around the area paint a nearly identical picture to the past several days, with widespread stratus and fog across the central and south Willamette Valley. Easterly flow through the Columbia River Gorge continues to keep the Portland/Vancouver metro mostly clear. Temperatures dropped into the 20s with patchy frost formation being observed in a few locations that are more sheltered from the wind. Expect more of the same tonight into Wednesday as stratus and fog remain trapped in the same areas beneath a strong subsidence inversion at around 1000 feet. Air stagnation issues will persist in these area through Wednesday as a result, with daytime temperatures continuing to struggle to get out of the 30s in the central and south Willamette Valley. Meanwhile, a TTD-DLS pressure gradient of -6 to -8 mb will maintain breezy conditions through the western Gorge through Wednesday, producing wind gusts to around 35 mph at times in eastern parts of the Portland metro and gusts as high as 60-70 mph at favored locations within the Gorge such as Corbett and Crown Point. This will also continue to keep the Portland area under mostly sunny skies, allowing afternoon temps to climb into the upper 40s each afternoon. Medium range guidance continues to hint at some changes in the pattern by Thursday as models are starting to come into better agreement on the ridge weakening enough to allow a weak upper level disturbance to cross the area on Thursday. It remains to be seen if this will result in any precipitation returning to the area as global ensembles have actually trended a bit drier for Thursday and Friday in recent runs, but there are still enough members depicting precipitation to keep a 20-30 percent chance of rain inland and a 50-60 percent chance along the coast for the latter half of the week. Regardless of how the forecast unfolds, any impacts look to be minimal as QPF amounts remain light and snow levels stay well above the Cascade passes. At the very least, the passing disturbance will be enough to weaken the subsidence inversion and finally put an end to air stagnation issues while scouring the stratus and fog out of the interior valleys. This will result in milder temperatures for Thursday and Friday, with overnight low more commonly in the upper 30s to low 40s as we head into the weekend. The weekend will also bring increasing chances for precipitation as the ridge axis finally shifts east of the Cascades and allows an upper level trough to potentially approach the region late Saturday into Sunday. DH/CB && .AVIATION...Continued pattern of nightly fog at the central and southern Willamette Valley terminals. Mixed IFR/LIFR conditions at those areas will transition to full LIFR by 08z or so, continuing for the rest of the night as thick fog remains in the area. Fog likely lifts Wednesday midday around 18-20z Wed, but redevelops Wednesday evening again. Less than 5% chance of fog reaching the northern Willamette Valley terminals during this period. With temperatures below freezing for much of the central and southern Valley, freezing fog is expected to be a concern for any terminals that will see fog. Rime icing will be possible in the coolest areas. Winds through the Columbia River Gorge continue to be strong, with gusts up to 30-35 kts at times throughout the duration of the TAF period. This should keep fog out of the north Valley. PDX AND APPROACHES...VFR conditions with clear skies throughout the period. Easterly winds under 10 kt at times due to strong winds from the Columbia River Valley. /JLiu && .MARINE...High pressure persists resulting in mild conditions across all waters through at least Wednesday night. Winds will remain under 10 kts and seas around 4 to 6 feet at 13 seconds. Expect strong ebbs to return to the Columbia River Bar around 5PM Tuesday and Wednesday with seas expected to be under 7 feet. Early Thursday morning, a weak front passing through the area will briefly elevate southerly winds, giving a 40%-60% probability of Small Craft Advisory conditions. Another, stronger front on Friday/Saturday will bring 50%-70% probability of Small Craft Advisory conditions with seas building towards 10 feet on Saturday and continuing to build into the mid to upper teens (50%-60% probability) by late Saturday/early Sunday and will likely remain in the low to mid teens for the start of next week. /42 && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Air Stagnation Advisory until 4 AM PST Thursday for ORZ104-105- 108-109-113>118-123>125. Freezing Fog Advisory until noon PST Wednesday for ORZ114>118. WA...Air Stagnation Advisory until 4 AM PST Thursday for WAZ202- 204>206-208. PZ...None. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland