FXUS66 KMFR 302109 AFDMFR Area Forecast Discussion National Weather Service Medford OR 209 PM PDT Mon Mar 30 2026 .DISCUSSION...A frontal system is strung out across the PacNW today, with radar imagery showing plenty of shower activity over southern Oregon and farn orthern California. A fast upper jet across NW Canada is sending a short wave trough through Washington/Idaho and into western Montana. The flow aloft isn't as strong to the south, and this is allowing another upper trough/low to spin offshore. Weak forcing along the frontal boundary will result in generally more cloud cover today than we've had the past few days, along with the continuing chance of showers, and temperatures about 5-15 degrees cooler for inland areas. The trough offshore will get a push eastward tonight into Tuesday and move inland. This could result in a broader area of light showers/rain, especially inland from the coast, but really, we're not expecting a washout by any stretch -- just an overall increase in shower chances with most areas experiencing long stretches in between without rain. The atmosphere destabilizes a bit over the East Side Tuesday afternoon and this brings a slight chance of thunderstorms (~20% chance) for portions of Modoc and Lake counties. At this point, any precipitation is welcome, especially given the dry, warm start to spring so far. A fairly drastic change is coming at midweek. Model guidance is nearly unanimous in bringing a strong upper trough southward from the Gulf of Alaska Wed/Thu. The leading edge of this system will be a cold front that will approach the coast Tuesday night, then move onshore Wednesday. The upper level cold pool will move onshore into Washington/Oregon Wednesday night into Thursday. Pressure gradients in advance of this system increase Wednesday afternoon, with mid-level winds peaking around 55 kt. This should result in widespread peak wind gusts in the 40-50 mph range for areas from the Cascades eastward, perhaps 55 mph in some areas. Wind advisories will likely be needed. The Shasta Valley will be breezy at least, due to the fairly strong pressure gradient, but the mid level flow will not be aligned with the terrain, keeping winds there weaker than may otherwise be expected, but still close to advisory level strength. The main frontal band will be accompanied by a period of light to moderate rainfall with the heaviest precipitation from the coast to the Cascades from late morning through the afternoon. We are NOT concerned about flooding with this event, other than some minor/typical nuisance ponding of water on roadways. Since river levels are very low for this time of year, most of the rain expected from this system will be beneficial/welcome. Amounts of 1-3 inches are likely along the coast, with 0.50-1.00 inch common inland to the Cascades with 0.25-0.50 inch over the East Side. Snow levels of 5000-5500 feet Wednesday will drop to around 2800 feet by Thursday morning. It looks like a pretty healthy snow storm for the Cascades and Siskiyous with 6-12 inches common above 5000 feet. A Winter Storm Watch has been issued for the Cascades, with additional advisories possibly needed for the 97 corridor and other portions of the Eats Side, and/or for the higher terrain of Siskiyou County. The heaviest snow will fall near Crater/Diamond Lakes and near Willamette Pass where it will be a bit colder, with NBM probabilities showing a high probability of >12 inches of snow. At Crater Lake (~7000 feet), the 48-hour probability of >18 inches of snow Wednesday into Thursday is 85%. We are also seeing some potential for spillover onto Highway 97 from around Chiloquin northward (Chemult/Crescent), especially Wednesday night into Thursday morning. There could be a few inches of snow in those areas. Expect winter travel impacts in the mountains and over some of the higher passes, especially at Lake of the Woods by Thursday morning. Main I-5 passes should be OK, but some slippery spots could develop at Siskiyou Summit and/or around Mt Shasta City/Snowman Summit early Thursday morning. With the core of the cold pool shifting into northeast Oregon and Idaho on Thursday, showers and even an isolated thunderstorm or two will continue for a while into Thursday afternoon, but then diminish rapidly around sunset Thursday evening as high pressure builds in. It should be noted that models are also showing a fairly high probability (50-70% chance) that temperatures drop into the low to mid 30s for the west side valleys by Friday morning. So, that will introduce some frost/freeze risk. Greatest risk of that occurring is in the Illinois Valley (Cave Junction/Obrien/Selma). The probability of temperatures less than 28F, however, are quite low, generally 10% or less. Models are showing the upper ridge rebuilding across the area Friday into the weekend, so look for temperatures to rebound to above normal levels again along with little to no chance at precipitation. && .AVIATION...30/18Z TAFs...A weak front will linger over the area through this evening. This will result in variable amounts of cloud cover and a chance of showers. Ceilings will be mainly VFR, but periods of MVFR and mountain obscuration will be possible. The highest probability of MVFR will be in Douglas County, including the Umpqua Valley and Roseburg, this morning. Expect another broader area of light rain showers to move through tonight into the wee hours of Tuesday, focused from near or just west of the Cascades over to the East Side. Best chance for MVFR ceilings and/or visibility will be in Klamath Falls tonight. && .MARINE...Updated 200 PM PDT Monday, March 30, 2026...Advisory strength north winds and steep seas will continue through tonight. Conditions briefly improve Tuesday with seas diminishing to around 4 ft. Seas are forecast to become steep with south gales early Wednesday and through the afternoon, and a Gale Watch has been issued. Steep seas are expected to become swell dominated on Wednesday night and build to a peak on Thursday. Advisory strength north winds are likely to return late in the week while seas remain steep. -Hermansen && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Winter Storm Watch from late Tuesday night through Thursday afternoon for ORZ025-027-028. CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT Tuesday for PZZ350-356-370-376. Gale Watch from late Tuesday night through Wednesday afternoon for PZZ350-356-370-376. && $$