505 FXUS66 KMFR 151621 AFDMFR Area Forecast Discussion National Weather Service Medford OR 921 AM PDT Tue Mar 15 2022 .DISCUSSION...An update is not necessary. The wind advisory for areas of Lake and Modoc counties will expire at 11 AM. This looks appropriate, but it warrants mentioning that southwest gusts will remain strongest near Summer Lake and Silver Lake at just below advisory levels, 30 to 40 mph, this afternoon through around 5 PM. A weakening cold front will continue across the east side during the remainder of this morning with isolated to scattered showers behind the front into early afternoon. Regarding additional disturbances to affect our area during the next week, a weak splitting trough may bring a few very light showers on Thursday. The focus for the afternoon forecast update will be upon the expected effects of a wet cold front Friday night into Saturday with showers likely to continue into Saturday night. Forecast uncertainty relates to the depth and track of the trough, which will impact the strength of subsequent ridging early next week. && .AVIATION...15/12Z TAFs... LIFR to IFR along and near the coast early this morning is likely to lift to a mix of IFR and MVFR late morning, and then, further, to a mix of MVFR and VFR this afternoon. Showers there are likely in the morning, with a lesser chance this afternoon. Across inland areas, a mix of conditions from IFR to VFR are being observed this morning as waves of precipitation move through in a general west-southwest flow. Showers are likely to mostly taper off this afternoon with VFR becoming more widespread. Gusty afternoon winds are likely, mostly along and east of the Cascades. ~BTL && .MARINE...Updated 325 AM PDT Monday 15 March 2022... Large, long period west to west-northwest swell is building this morning in the wake of yesterday's cold front. This swell has come in a bit heavier than was previously expected and is likely to peak in the 14 to 18 foot by 19 second range this morning. A High Surf Advisory has been issued for this morning due to increased wave hazards along the coast in and near the surf zone due to the incoming heavy swell. Seas are expected to gradually subside this afternoon through Wednesday. Relatively calm conditions will then prevail Thursday into Friday. ~BTL && .PREV DISCUSSION... /Issued 640 AM PDT Tue Mar 15 2022/ SHORT TERM... Widespread rain showers cover the warning area this morning as a cold front and upper level trough moves through. Snow levels are starting out around 6000 feet this morning. Most of the DOT cameras do show rain below this level at this time. Snow levels will lower down to 4500 feet once the cold front moves through, which will result in some snow accumulation over the higher Cascades near Crater Lake. As this cold air filters in, we'll see some instability over the forecast area. Convective available potential energy is around 150 J/kg across a pretty broad area. We took a brief gander at the potential of thunder on the national blend of models and it shows values between 10 to 15 percent. We don't have thunder in the official gridded forecast as the probabilities are below 15 percent, yet the environment is still supportive for some rumbles of thunder later this afternoon. By tonight, the upper level low moves eastward. The colder air will be noticeable overnight as temperatures trend 10 degrees cooler. Partial clearing overnight will help most valleys fall into the mid 30's west of the Cascades with 20's on the eastside. It's worth noting normal lows are indeed in the mid 30's for valleys west of the Cascades this time of year. An upper level ridge begins to build in during Wednesday with some of the cold air aloft remaining place. We'll probably see some fair weather cumulus across the region as the atmosphere remains fairly unstable and some boundary layer moisture lingers. Other than that, Wednesday should be a rather quiet and uneventful spring day. -Smith LONG TERM.../Issued 242 PM PDT Mon Mar 14 2022/ Thursday through Monday, March 17-21, 2022... Split flow developing Wednesday night into Thursday will feature short wave ridging shifting east of the Cascades, allowing weak Pacific disturbances to move through on Thursday. The best moisture and energy is associated with a northern branch feature, which will graze our NW sections with some clouds and perhaps a little rain. A second short wave will dive southeastward into California resulting in an elongated trough zipping through NorCal and southern Oregon. Moisture levels with this aren't really sufficient to produce much in the way of precipitation. As such, there is a just a chance of showers (20- 50%) for areas along and west of the Cascades. Even in areas that stand the best chance for rainfall, amounts will be light, generally only a hundredth or two, but perhaps up to a tenth of an inch from Reedsport northward. On Friday, models continue to show another robust frontal system and upper trough reaching our coast by late afternoon. The front is expected to move onshore Friday evening with precipitation spreading inland to the Cascades, then eventually shifting east of the Cascades and across NorCal overnight Friday into Saturday morning. Widespread wetting rainfall is likely with this front again with preliminary estimates of liquid precipitation showing another 1-2" along the coast and 0.50-1.00" for the Cascades and portions of southern/western Siskiyou County. The west side valleys are shown to receive 0.25-0.50" with generally 0.10-0.25" over the East Side. Snow levels with this system likely start up around 6000 feet Friday evening, then lower to 3500 feet Saturday. Potential snowfall over the mountains above 4500 feet could be 5-10 inches. Model pressure gradients and wind fields with this front are not that strong at this time, but could still see some breezy south to southwest winds in advance of the front Friday/Friday night. Post-frontal showers continue Saturday afternoon through Saturday night with a colder air mass descending upon the region. Snow levels could drop to around 1500-2000 feet as precipitation gradually diminishes by Sunday morning. As we discussed yesterday, behind Sunday's departing upper trough, models are showing an upper ridge building off the West Coast early next week. Cluster analysis today shows two main solutions, one with a strong, more amplified ridge that would keep the main storm track well to our north resulting in a dry, very mild pattern. The other shows a flatter, yet broad ridge, with northern branch disturbances directed into the PacNW. This could bring some precipitation into Oregon at times, but with a sharp cutoff in precip farther south. The NBM shows a chance of rain across NW sections of the forecast area during this time period, but many of the ensemble members are completely dry. While we aren't totally sure about the ridge winning out at this point, given what's happened most of this winter, we're inclined to believe that's what will happen. -Spilde && .MFR WATCHES/WARNINGS/ADVISORIES... OR...High Surf Advisory until noon PDT today for ORZ021-022. Wind Advisory until 11 AM PDT this morning for ORZ030-031. CA...Wind Advisory until 11 AM PDT this morning for CAZ085. Pacific Coastal Waters... Small Craft Advisory until 5 PM PDT Wednesday for PZZ350-356-370-376. $$ DW/Sven