419 FXUS66 KMFR 131111 AFDMFR Area Forecast Discussion National Weather Service Medford OR 411 AM PDT Wed Apr 13 2022 .SYNOPSIS...We remain under the influence of a broad upper level low as part of an omega block. This will keep us in a generally active pattern for the next couple of days as conditions begin to moderate and it breaks down. Another cold front approaching on Friday will time up with an atmospheric river, and could produce some additional rain and snow. The active weather will continue after a brief break over the weekend with additional frontal systems coming in, providing some relief to our dire snowpack situation. && .SHORT TERM...Today through Thursday night...Radar imagery is showing a broad area of showers across most of southern Oregon and northern California. Modoc County, so far, is the only one without showers and satellite imagery indicates that area is experiencing clear skies as well. The showers will continue for much of the day today as our next impulse of moisture arrives this afternoon and evening, driven by an upper level low to our northwest that is broad and wobbling around offshore. This next impulse looks to favor more northern California, with a still westerly trajectory. Snow levels remain relatively low, but will rise this afternoon to around 3000 feet or so (except for in the Umpqua Basin where they remain around 2000 feet). Like yesterday, any heavier showers will bring down snow levels during periods of heavy precipitation, allowing for snow or accumulating graupel once again. Winter weather products are continuing across much of the area along and west of the Cascades through this morning, and then an additional advisory will begin up in the Mt. Shasta City Area, Highway 89, and Snowmans Summit, largely above 3500 feet. More information will be available in the WSWMFR. Will also be evaluating whether or not to extend advisories in western Siskiyou County due to additional snows, this time above 3500 feet for tomorrow night. That will be happening in the next couple of hours. Additionally, this impulse may create some breezy to gusty conditions east of the Cascades this afternoon, but guidance is suggesting that winds will remain just below advisory conditions for now. Thu night into Friday we'll catch a relative break, overall, but the frontal boundary and precip may get hung up over NE CA and then wave northward later on Friday. -Schaaf .LONG TERM...From Friday until Wednesday morning... Friday will start out mainly dry with gradual showers dissipating in the morning. The next system will arrive in the afternoon or evening time frame, and ensembles are now suggesting a different synoptic look. Warmer, moister air will arrive from the southwest, however it is now looking like it will line up with a cold front. This sort of pattern happened last (at least in my memory) in February 2019. Although the storm in 2019 was a bit stronger than this one, and the fact we are in Mid April suggests that impacts will be a bit less. Still this could be another situation of vast moisture with relatively low snow levels. This is an admitted shift from the previous forecast, and have gone with the NBM as the main ensemble solution here. The nuance, as it was in 2019, was that the location of the cold front relative to the atmospheric river will be key in deciding what the impacts will be (snow levels around 5500 feet per the previous forecast or 2500 to 3500 feet with this forecast). Regardless, we'll likely see more snow accumulate in the mountains with up to 12 inches possible over the higher mountains in California and around Mt. Ashland. In addition, the Cascades could still see 4 to 8 inches. The other part of the forecast that gives me low confidence in the forecast is the location of where the atmospheric river will make landfall. Right now it favors the Calfiornia/Oregon border, but the GEFS could suggest it to be farther south, which would lower precipitation amounts and duration. Saturday may continue the precipitation in showers, as they dissipate leading to a mainly dry Sunday. Then, heading further into the extended forecast, the activity just keeps on going with the ensembles showing integrated water vapor transport(IVT) values up to 500. It looks like this is centered around April 19th, but there is some variation that the higher IVT values could come in a bit earlier or later than that. The take home point here is another swath of precipitation should be arriving early next week. The other notable feature here is the south westerly component in the IVT vector. This suggests this AR will be warmer with higher snow levels. The NBM is forecasting snow levels up to 6000 feet around the 19th. It indeed could go higher as the southerly ARs in spring like to go up to 8000 feet. -Schaaf/Smith && .AVIATION...13/06Z TAFs...An unstable atmosphere will remain over the area through the next 24 hours. Gusty winds and isolated thunderstorms are possible along the coast into Wednesday. Gusty west winds will continue over higher terrain overnight. A mix of IFR and MVFR ceilings continue at the coast, with generally VFR ceilings and mountain obscuration inland. As showers increase overnight and into Wednesday as more energy enters the forecast area, ceilings will likely lower to MVFR. Additionally, low visibility at KLMT is expected early this evening and again Wednesday when snow is expected to affect that area. Freezing levels will remain low into tonight, around 2000 to 3000 feet above MSL, under a cold air mass. Keene && .MARINE...Updated 200 AM PDT Tuesday, 12 April 2022...Moderate winds will continue into this morning, then gradually diminish this afternoon. At the same time, seas will also gradually diminish. The one concern today will be a slight chance for thunderstorms mainly over the northern waters due to an unstable air mass, and locally gusty winds are possible near any of these storms. Relatively calmer conditions in terms of winds and seas are expected this evening through Friday afternoon. Weak low pressure will move north of the waters Wednesday morning. Another weak low will move south of the waters Wednesday night into Thursday morning, followed by another one Friday night. -Petrucelli && .MFR WATCHES/WARNINGS/ADVISORIES... OR... Winter Weather Advisory until 11 AM PDT this morning above 2000 feet in the for ORZ024-026. Winter Weather Advisory until 11 AM PDT this morning above 1500 feet in the for ORZ023. Winter Storm Warning until 11 AM PDT this morning for ORZ025. Winter Weather Advisory until 11 AM PDT this morning for ORZ028. Winter Storm Warning until 11 AM PDT this morning for ORZ027. CA...Winter Weather Advisory from noon today to 11 AM PDT Thursday above 3500 feet in the for CAZ082-083. Winter Weather Advisory until 11 AM PDT this morning above 2000 feet in the for CAZ080. Pacific Coastal Waters... Small Craft Advisory until 5 PM PDT this afternoon for PZZ350-356-370-376. $$