FXUS66 KMFR 040522 AFDMFR Area Forecast Discussion National Weather Service Medford OR 922 PM PST Tue Dec 3 2024 ...Updated Aviation Section... .AVIATION (06Z TAFs)... Valley fog has returned to the westside valleys, and is expected to impact both Roseburg and Medford tonight through tomorrow morning with IFR/LIFR conditions. Expecting fog to burn off in a similar fashion as today with return to VFR conditions across all four terminals by tomorrow afternoon. Wind speeds through this stretch will be mostly light and variable. -Guerrero && .MARINE... && .PREV DISCUSSION... /Issued 845 PM PST Tue Dec 3 2024/ DISCUSSION...Made a few adjustments to tonight's forecast based on current satellite and the expectation of fog/low clouds to redevelop in the valleys west of the Cascades. If you encounter dense fog tonight or Wednesday morning, please slow down and take some extra time. In areas where it's near or below freezing, icy spots may be on the roadways, especially bridges and overpasses. The low visibility in areas of dense freezing fog and icy spots will make driving conditions hazardous. Expect lows from the upper 20s to the mid 30s in these valley areas. East side areas should remain mostly clear with lows in the teens and 20s, the exception being the Klamath Marsh area, where temps could drop to the single digits. -Spilde AVIATION...04/00Z TAFS...VFR conditions prevail over most of the area this evening. However, LIFR stratus and fog is reforming in the Umpqua Basin, the Illinois Valley and also the Rogue Valley near Grants Pass. Expect most of the valleys that had fog/low clouds last night and this morning west of the Cascades will fill in with LIFR fog and low clouds again this evening 05-08Z, then persist into Wednesday morning. Clearing to VFR will occur in most areas Wednesday afternoon, though the usual spots (Grants Pass and the Illinois/Umpqua valleys could hold it most of the day. -BPN/Spilde MARINE...Updated 800 PM PST Tuesday, December 03, 2024...Light to moderate north winds and relatively calm swell dominated seas will persist into Wednesday. A weak front is expected to pass by just to the north, with winds shifting to southerly. Seas will build, with west swell dominated seas just shy of becoming steep as they peak on Thursday night. A stronger front will move through Friday night into Saturday morning with the highest winds and seas approaching advisory levels north of Cape Blanco on Saturday. A third front is forecast to be the strongest of the bunch with large and steep swell dominated seas possible early Sunday into early Monday. -BPN/DW PREV DISCUSSION... /Issued 220 PM PST Tue Dec 3 2024/ DISCUSSION...Satellite image shows low clouds lingering in portions of the Umpqua Basin Illinois Valley and in the Grants Pass area. The low clouds are slowly burning off, but those areas should break out late in the day before becoming socked in again early this evening. Elsewhere, it's clear. We'll have a rinse and repeat scenario with respect to the development of low clouds, fog and freezing fog later this evening through at least tomorrow morning impacting the same areas as this morning. Areas that experience freezing fog (Illinois Valley, Grants Pass area, Rogue, Shasta, and Scott Valley) will result in low visibility along with slick driving conditions for the early morning commute, especially on bridges and any other elevated roads because of not warming from the ground below. Dry weather is likely to continue through Wednesday night. A weak warm front could bring a slight chance of precip along the coast, north of Cape Blanco Thursday morning, but the front is likely to weaken as it moves into the ridge. Therefore precipitation will be limited to the north coast, and not make much if any headway inland. Even then rainfall amounts should only amount to a few hundreths of an inch at best. Thursday afternoon is likely to be dry as the aforementioned front continues to weaken and dissipate. The one thing the front will do is bring more cloud cover to the area Wednesday night into Thursday morning, with the cloud cover thickest in the Umpqua Divide. This should keep temperatures from dropping down below freezing. Farther south, in portions of the Rogue parts of the Illinois, Shasta, and Scott Valleys, the cloud cover may not be sufficient enough to keep temperatures from dropping below freezing, so we could be dealing with another round of freezing Fog later Wednesday night into Thursday morning. Dry weather is likely Friday with upper ridging building into the area. The main variable will be the extent of cloud cover and will it be sufficient enough to keep low clouds and fog from forming. For now, kept it out of the forecast, but this will need to be looked at again. A stronger upper trough will approach the area Saturday, with a surface front pushing into the area. This will bring light precipitation primarily along and west of the Cascades. The operational models and about a third of the ECMWF individual ensemble members show some precipitation in the above mentioned areas. Upper troughing remain over the area Sunday with a few showers possible west of the Cascades, then there's good agreement among the operational, ensembles and clusters showing upper ridging building back in by the start of next week and could last into at least the middle of next week with dry weather becoming more likely. -Petrucelli && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Air Stagnation Advisory until 4 PM PST Friday for ORZ023-024-026- 029>031. CA...None. PACIFIC COASTAL WATERS...None. && $$