AFDMFR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MEDFORD OR 349 AM PST SUN DEC 5 2021 .DISCUSSION...SATELLITE IMAGERY SHOWS FOG/STRATUS ACROSS BOTH CALIFORNIA AND OREGON VALLEYS, PARTICULARLY ON THE WEST SIDE EARLY THIS MORNING. ADDITIONALLY, SOME HIGHER CIRRUS CLOUDS ARE OBSCURING SOME OF THE FOG FROM THE SATELLITE VIEWER, BUT GROUND OBSERVATIONS ARE SHOWING THE LOW STRATUS AND FOG CONTINUING, WITH SOME AREAS EVEN SEEING DRIZZLE THAT CONTINUES TO MEASURE IN THE MORNINGS. TODAY SHOULD BE THE LAST DAY OF HIGH PRESSURE BEFORE THE PATTERN SHIFTS TOWARDS MORE ACTIVE WEATHER. AN AIR STAGNATION ADVISORY REMAINS IN EFFECT FOR THE ROGUE AND ILLINOIS VALLEYS THROUGH EARLY MONDAY MORNING. IT IS WORTH NOTING THAT IN PLACES WITH A STRONG INVERSION, THE TEMPERATURE RANGES HAVE BEEN VERY SMALL (LESS THAN 10 DEGREES). OVERALL, EXPECT THE AREA TO BE A BIT COOLER TODAY AS COMPARED TO YESTERDAY. THEN, TONIGHT THE FIRST OF SEVERAL SYSTEMS WILL ARRIVE IN SOUTHERN OREGON AND PUSH SOUTHWARD INTO NORTHERN CALIFORNIA. THIS SYSTEM CONTINUES TO TREND A BIT WEAKER THAN DURING PREVIOUS MODEL CYCLES, AND PRECIPITATION WILL LIKELY BE RELATIVELY LIGHT, ALBEIT NOTICEABLE. SNOW LEVELS AROUND 6000 TO 7000 FEET WILL KEEP IMPACTS RELATIVELY MINIMAL WITH THIS EVENT. THE BIGGEST IMPACTS WILL PROBABLY BE WINDS, PARTICULARLY ON THE EAST SIDE. BUT EVEN THEN, THE MODELS HAVE TRENDED THIS A BIT WEAKER AS WELL. OVERALL, THE FORECAST REMAINS ONE FOR RAIN, FOCUSED ON THE WESTERN SLOPES AND FOOTHILLS, BREEZY BUT NOT STRONG WINDS, AND VERY LIGHT MOUNTAIN SNOW ALMOST EXCLUSIVELY ABOVE 5000 FEET. SHOWERS ARE LIKELY TO CONTINUE INTO MONDAY NIGHT WEST OF THE CASCADES, BUT IN THE END, PRECIPITATION AMOUNTS WILL NOT BE SIGNIFICANT. THE GOOD NEWS IS, THERE SHOULD BE ENOUGH WIND TO BREAK THE PERSISTENT INVERSION IN THE VALLEYS, CLEARING THE AIR AT LEAST TEMPORARILY. ...PREVIOUS LONG TERM (SAT DEC. 4TH)...TUESDAY THROUGH SATURDAY NIGHT...A RELATIVE BREAK IN THE WEATHER IS EXPECTED TUESDAY. ANY SHOWERS THAT ARE AROUND SHOULD BE MAINLY ALONG THE COAST AND NORTHWEST DOUGLAS COUNTY. EVEN THEN PRECIPITATION AMOUNTS ARE EXPECTED TO BE LIGHT. THE OPERATIONAL GFS IS A BIT MORE ROBUST WITH PRECIPITATION AMOUNTS DUE TO A STRONGER UPPER TROUGH MOVING INTO THE AREA. HOWEVER, THE MAJORITY OF THE INDIVIDUAL GFS ENSEMBLE MEMBERS SHOW NO PRECIPITATION ON TUESDAY AND THE SAME CAN BE SAID FOR THE ECMWF INDIVIDUAL ENSEMBLE MEMBERS. BECAUSE OF THE ABOVE REASONING, HAVE LEANED TOWARDS THE LOW END OF THE SPECTRUM FOR POPS ON TUESDAY. THE NEXT FRONT WILL QUICKLY MOVE IN WEDNESDAY. PRECIPITATION ASSOCIATED WITH IT IS NOT ROBUST WITH MOST CENTERED ALONG AND WEST OF THE CASCADES GIVEN A FAST WEST TO NORTHWEST FLOW WHICH TYPICALLY RESULT IN LITTLE OR NO PRECIPITATION EAST OF THE CASCADES. HOWEVER THE EAST SIDE WILL BE WINDY, ESPECIALLY IN THE AFTERNOON AND EARLY EVENING HOURS. 500MB HEIGHTS WILL FALL WEDNESDAY NIGHT AS BROAD UPPER TROUGHING BEGINS TO MOVE INTO THE FORECAST AREA WHICH COULD LAST THROUGH THURSDAY BEFORE MOVING EAST OF THE AREA AS UPPER RIDGING BUILDS IN FRIDAY AND LASTING INTO THE START OF NEXT WEEKEND. WHAT THIS WILL DO IS BRING LOWERING SNOW LEVELS WHICH COULD GET DOWN TO AROUND 2500 FEET AS A S A SECONDARY IMPULSE TRAVELS ALONG THE LONG-WAVE TROUGH IN OUR AREA. THIS WILL ALLOW SNOW LEVELS TO FALL FURTHER AND COULD GET CLOSE TO THE VALLEY FLOOR AT AROUND 1400 FEET. HOWEVER, THE LIMITING FACTOR WILL BE PRECIPITATION. IF ANYTHING WERE AROUND, IT WOULD BE VERY LIGHT AND ISOLATED. ALTHOUGH ENSEMBLES ARE CONTINUING TO SUGGEST THAT SNOW WILL BE POSSIBLE ON THE VALLEY FLOORS, THE REALITY IS THIS SCENARIO IS A BIT MORE UNLIKELY THAN WHAT THE ENSEMBLE PERCENTAGES SHOW. THE CONSENSUS AMONG THE OPERATIONAL MODELS AND ENSEMBLE MEMBERS (BOTH THE ECMWF AND GFS) ARE POINTING TOWARDS UPPER RIDGING BUILDING INTO THE AREA FRIDAY INTO SATURDAY MORNING, BUT WILL BE SHORT LIVED AS A STRONGER AND DEEPER UPPER TROUGH BUILDS IN FROM THE GULF OF ALASKA SATURDAY AND COULD PERSIST INTO THE START OF THE FOLLOWING WEEK (DECEMBER 12-17). THE ECMWF AND ENSEMBLE MEMBERS ARE SLOWER TO BRING THE TROUGH AND ASSOCIATED FRONT INTO THE AREA WHICH IS DUE IN PART THE FRONT BEING NEARLY PARALLEL TO THE UPPER FLOW AND THE UPPER TROUGH DEEPENING FURTHER OFFSHORE WHICH TYPICALLY RESULTS IN A SLOWER PROGRESSION OF THE FRONT. -PETRUCELLI && .AVIATION...05/06Z TAFS...MORE OF THE SAME WITH IFR AND LIFR CONDITIONS WITHIN A FEW VALLEYS WEST OF THE CASCADES TONIGHT. A COLD FRONT IS ALSO GENERATING SOME LOW TO MID LEVEL CLOUDS AND CREATING MVFR CEILINGS ALONG THE COAST AND INTO THE UMPQUA VALLEY. BE ON THE LOOK OUT FOR LIFR CEILINGS AGAIN IN THE VALLEYS WEST OF THE CASCADES AND ALONG THE COAST TONIGHT. EAST OF THE CASCADES, LIFR VISIBILITIES WILL LIKELY BUILD IN LMT AND SECTIONS OF THE KLAMATH BASIN. BY THE DAYTIME, WE`RE FORECASTING LOCATIONS EAST OF THE CASCADES AND THE UMPQUA VALLEY TO CLEAR OUT BY THE AFTERNOON HOURS. IT LOOKS LIKE SOME OF THE VALLEYS NEAR MFR WILL STAY STUCK IN IFR TO LIFR CONDITIONS. -SMITH && .MARINE...UPDATED 230 AM PST SUNDAY, DECEMBER 5, 2021...A COLD FRONT IS BRINGING GUSTY NORTH WINDS AND STEEP SEAS TO THE NORTHERN WATERS EARLY THIS MORNING. THE FRONT IS WEAKENING, BUT MODERATE NORTH WINDS AND CHOPPY SEAS ARE EXPECTED BEHIND THE FRONT TODAY. SEAS WILL SUBSIDE SOME TONIGHT. SEAS ARE FORECAST TO BUILD AROUND THURSDAY AND FRIDAY AS MORE STORMS DEVELOP OFFSHORE. MORE SPECIFICALLY, LATEST DATA SUGGESTS A LARGE SWELL OF 15 FT AT 13 SECONDS ARRIVING FRIDAY MORNING AS THE WEATHER PATTERN BECOMES MORE ACTIVE OVER THE NORTHEAST PACIFIC WATERS. KEENE && .MFR WATCHES/WARNINGS/ADVISORIES... OR...AIR STAGNATION ADVISORY UNTIL 4 AM PST MONDAY FOR ORZ024-026. CA...NONE. PACIFIC COASTAL WATERS... SMALL CRAFT ADVISORY UNTIL 4 AM PST EARLY THIS MORNING FOR PZZ350-370-376.