FXUS66 KMFR 232150 AFDMFR Area Forecast Discussion National Weather Service Medford OR 250 PM PDT Wed Oct 23 2024 .DISCUSSION...An upper level cold front is moving over northern California and southern Oregon this afternoon. Showers have been observed at isolated locations and activity will continue moving eastward and out of the area through the evening. A Freeze Warning is in place for Thursday morning from 2 AM through 10 AM as cold air behind the front moves into area valleys. In Oregon, the Warning covers the Illinois, Applegate, and Rogue valleys as well as southern Douglas County including the cities of Azalea and Glendale. In California, the Warning covers the Lower Klamath River, Scott, and Shasta valleys as well as the Mount Shasta region. These areas have high chances (50-90+%) to experience periods of freezing conditions during the Warning duration. An upper level ridge will start to develop during the day on Thursday, bringing a warming trend that will continue into Saturday. A thermal trough will help parts of southwest Oregon (including Brookings, Gold Beach, and Agness) to get a head start on warming on Thursday. Friday morning lows have 40-80% chances to remain near frost conditions (33 to 36 degrees) in most areas affected by the Thursday morning Warning, with cities in the southern Rogue Valley (Ashland, Phoenix, Talent) unlikely to see frost conditions in this period. More active weather will begin on Friday evening into Saturday morning, when a low pressure system will move down from the Gulf of Alaska and linger off the Canadian coast. A warm front from this system will brush along the Oregon coast starting Friday evening. This front will bring a 60-95% chance of showers along coastal areas and a 40-80% chance over inland areas through the day Saturday. With these constant chances for light showers, Curry County and coastal Coos County are forecast to get between 0.5 and 1.0 inches of rainfall on Saturday. Other inland areas west of the Cascades will see 0.2 inches or less in this period. On Sunday morning, a cold front from the low pressure system will start to move over the area, bringing a wave of activity across the area. 70-95% chances of precipitation will move eastward through the day Sunday. Curry County will see heavy rainfall late Saturday night into early Sunday morning, with another 0.5 to 1.0 inches expected in this short period. A cold upper trough is expected to deepen and move over the area behind the front, supporting scattered post- frontal showers through Monday and Tuesday. Overall, Coos and Curry counties and the Cascades will get between 1 and 2 inches of precipitation from Sunday to Tuesday. The Umpqua Valley is forecast to get about an inch of rainfall and the Illinois and Rogue valleys will get between 0.5 and 0.75 inches of rainfall in this period. Other areas will get half an inch or less of rainfall into next week. Snowfall over the Cascades is possible behind the cold front, but the timing is complicated. The heaviest precipitation over the Cascades is later in the morning on Sunday, but snow levels are forecast to be above 7000 feet at this point. Snow levels are expected drop to 5000-6000 feet by Monday morning and 4000 feet by Tuesday morning. ECMWF and GFS model guidance suggests between 3 to 6 inches of snow over the Cascades early next week, while the NBM expects 5 to 10 inches along the range and 12 inches at higher elevations. This far out, there's many variables that could impact total snowfall that are difficult to accurately forecast. Additionally, lingering surface warmth and rain/snow mixes would likely minimize widespread accumulation. At the very least, widespread winter weather hazards are not expected but some products are not impossible. Beyond Tuesday, activity is expected to decrease. Both GFS and ECMWF precipitation meteograms suggest an unimpactful front moving over the area late next week, then sporadic signals beyond that. Temperature meteograms keep temperatures cool through the first couple weeks of November. -TAD && .AVIATION...23/18Z TAFs...A front forming over the region late this morning continues to bring widespread cloud cover, though mostly VFR as of this writing (1030 am PDT). However, lower ceilings (MVFR) persist in the Umpqua/Rogue valleys along with areas of higher mountain obscuration. The front will slowly shift eastward this afternoon, pushing east of the Cascades after 22Z and clearing eastern Lake County by as late as 02Z. Some light rain and higher elevation snow will accompany the front as it moves through, perhaps briefly lowering ceilings to MVFR in some areas that are VFR currently. Ceilings improve rapidly after the front moves through late this afternoon/evening as much drier air moves in aloft. Winds will generally remain light for inland portions of the west side into Thursday morning, but west to northwest winds will be breezy this afternoon on the eastside, including Klamath Falls. Tonight into Thursday morning, valley MVFR/IFR is expected early Thursday morning, particularly in the Umpqua Valley, but most everywhere else will be VFR. -Spilde && .MARINE...Updated 200 PM PDT Wednesday, October 23, 2024...A thermal trough near the coast will bring moderate north winds and elevated seas over the marine waters tonight through late Thursday evening. The worst conditions will be beyond 10 nm from shore and south of Cape Blanco. A brief period of improved conditions is expected early Friday before a pattern change that is expected late Friday through the weekend. Low pressure moving north toward Vancouver Island will bring increasing southerly winds and building seas late Friday afternoon and Friday night, with gales and very steep, hazardous seas possible. Steep southwest swell is then likely to continue behind the low Saturday with active weather persisting into early next week. -Spilde && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Freeze Warning from 2 AM to 10 AM PDT Thursday for ORZ023-024- 026. CA...Freeze Warning from 2 AM to 10 AM PDT Thursday for CAZ080>082. PACIFIC COASTAL WATERS...Gale Watch from Friday afternoon through late Friday night for PZZ370-376. Small Craft Advisory until 2 AM PDT Friday for PZZ376. && $$ TAD/MAS