090
FXUS66 KMFR 122221
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
221 PM PST FRI DEC 12 2025
DISCUSSION
MUCH LIKE YESTERDAY AT THIS TIME, SATELLITE IMAGE
SHOWS LOW CLOUDS PERSISTING IN THE ROGUE, ILLINOIS, AND SHASTA
VALLEYS. LOW CLOUDS ARE GRADUALLY BURNING OFF IN THE KLAMATH RIVER
AND SCOTT VALLEYS AND THE UMPQUA BASIN. ELSEWHERE IT'S CLEAR AND
WILL REMAIN CLEAR THROUGH THIS EVENING. IT'S LIKELY THE LOW CLOUDS
WILL PERSIST ROGUE AND ILLINOIS VALLEY THROUGH THE AFTERNOON AND
TONIGHT. WHAT THIS WILL DO IT LIMIT OR EVEN PREVENT FOG FROM FORMING
IN THESE AREAS LATER TONIGHT. HOWEVER, LOW CLOUDS AND FOG ARE LIKELY
AGAIN IN THE VALLEYS IN DOUGLAS COUNTY, SCOTT, KLAMATH RIVER, AND
SHASTA VALLEY LATE THIS EVENING THROUGH SATURDAY MORNING.
MEANWHILE, LOW CLOUDS AND FOG SHOULD BURN OFF LATE THIS AFTERNOON IN
THE SHASTA VALLEY, ONLY TO RE-FORM AGAIN LATE THIS EVENING AND
LASTING THROUGH AT LEAST EARLY SATURDAY AFTERNOON.
THE OVERALL PATTERN IS NOT GOING TO CHANGE MUCH THROUGH SATURDAY
WITH STRONG UPPER RIDGING KEEPING THE STORM TRACK WELL NORTH OF THE
FORECAST AREA. THIS MEANS CONTINUED DRY AND MILD WEATHER (WHERE LOW
CLOUDS AND FOG ARE ABSENT). THE LOW CLOUDS AND FOG FOR THE AREAS
MENTIONED ABOVE WILL KEEP AFTERNOON TEMPERATURES IN CHECK TODAY AND
SATURDAY AND THEY HAVE BEEN ADJUSTED LOWER TO REFLECT THIS. IT'S NOT
OUT OF THE QUESTION LOW CLOUDS IN THE ROGUE AND ILLINOIS VALLEY WILL
PERSIST THROUGH SATURDAY AFTERNOON AS WELL.
THE UPPER RIDGE WILL WEAKEN SLIGHTLY AS A WEAK FRONT MOVES IN FROM
THE WEST SUNDAY. GIVEN THE WEAK SHORTWAVE AND SURFACE FRONT WILL BE
RUNNING INTO THE STRONGER UPPER RIDGING, THE MOST LIKELY SCENARIO IS
THE FRONT WILL WEAKEN AND DISSIPATE AS IT REACHES THE COAST SUNDAY
AFTERNOON. PER THE USUAL THE NBM SOLUTION IS TOO BULLISH (MEANING
POPS ARE TOO HIGH AND TOO FAR INLAND) WHICH DOES NOT ADD UP GIVEN
THE ABOVE MENTIONED. TO FURTHER SUPPORT THIS THINKING, THE MAJORITY
OF THE INDIVIDUAL ENSEMBLE MEMBERS ALSO SHOW THE FRONT WEAKENING AND
DISSIPATING AS IT REACHES THE COAST AND INLAND.
SUNDAY IS LIKELY TO END UP BEING THE LAST QUIET DAY OF THE FORECAST
PERIOD. THE OPERATIONAL MODELS AND ENSEMBLES HAVE BEEN SHOWING FOR
THE PAST FEW DAYS A MORE ACTIVE PATTERN SETTING UP BY THE START OF
NEXT WEEK. IN A RELATIVE SENSE, IT WILL SEEM LIKE A SIGNIFICANT
CHANGE WITH BOUTS OF MODERATE TO HEAVY RAIN AND MOUNTAIN SNOW ALONG
WITH MODERATE TO STRONG WINDS POSSIBLE AT THE COAST, AND EAST OF THE
CASCADES ON MONDAY. HOWEVER, IT'S NOT ALL THAT UNUSUAL TO HAVE
ACTIVE WEATHER OF THIS MAGNITUDE THIS TIME OF THE YEAR.
THE FIRST FRONT WILL ARRIVE AT THE COAST EARLY MONDAY MORNING
BRINGING RAIN AND MODERATE TO OCCASIONALLY STRONG WINDS TO THE COAST,
NORTH OF CAPE BLANCO. PRECIPITATION WILL MOVE INLAND DURING THE DAY
MONDAY, WITH WINDS INCREASING EAST OF THE CASCADES.
THE CHANGE IN THE PATTERN IS ONE WHERE WE'LL SEE A PARADE OF FRONT
MOVING THROUGH THE AREA FROM MONDAY-FRIDAY NEXT WEEK BRINGING MORE
RAIN, MOUNTAIN SNOW AND MODERATE TO OCCASIONALLY STRONG WINDS.
THE MAIN ISSUE WILL BE THE TIMING AND EXACT TRACK OF OF EACH
INDIVIDUAL SYSTEM WHICH IS LIKELY TO VARY FROM DAY TO DAY.
LOOKING BEYOND NEXT WEEK LEADING UP TO CHRISTMAS HOLIDAY, THERE'S
INCREASING EVIDENCE THAT'S BEING SUPPORTED BY THE ECMWF, GEFS
ENSEMBLE MEANS AND CLUSTERS, WE'LL BE HEADING INTO A COLDER AND WET
PATTERN WITH STORMS ORIGINATING FROM THE GULF OF ALASKA AS WE GET
TOWARDS THE FOLLOWING WEEKEND INTO CHRISTMAS WEEK.
THESE TYPICALLY RESULT IN COLDER TEMPERATURES, AND PRECIPITATION
WITH LOWER SNOW LEVELS. THE PATTERN SHOWS BELOW NORMAL 500 MB
ANOMALIES WITH A STRONGER UPPER TROUGHING IN THE WESTERN U.S. WITH
RIDGING AND ABOVE NORMAL 500 MB ANOMALIES IN THE NORTHEASTERN PART
OF THE U.S. THE ANOMALIES BEING SHOWN ARE PRETTY SIGNIFICANT THIS
FAR OUT WHICH IS UNUSUAL SINCE THEY TEND TO "WASH OUT" AND LEAN MORE
TOWARDS CLIMATOLOGY.
THIS IS A ALMOST THE OPPOSITE OF THE PATTERN WE HAVE EXPERIENCED FOR
ALMOST THE LAST THREE WEEKS, WITH STRONGER RIDGING IN THE WESTERN
PART OF THE U.S. AND DEEP UPPER TROUGHING IN THE NORTHEASTERN PART
OF THE U.S. IN OTHER WORDS, THE SWITCH BASICALLY GETS FLIPPED AS THE
OVERALL PATTERN CHANGES. -PETRUCELLI
AVIATION...12/18Z TAFS
VERY LITTLE CHANGE IN THE PATTERN IS
LIKELY IN THE NEXT 24 HOURS. AREAS OF LOW STRATUS AND FOG ARE
PRESENT IN VALLEYS WEST OF THE CASCADES, INCLUDING IFR IN THE ROGUE
VALLEY AT MEDFORD AND GRANTS PASS AND LIFR IN FOG IN THE SHASTA
VALLEY, AND THE UMPQUA BASIN, INCLUDING ROSEBURG AND COQUILLE
VALLEYS. THESE CONDITIONS WILL PERSIST THROUGH 20Z. SOME AREAS, SUCH
AS MEDFORD AND GRANTS PASS WILL SEE CEILINGS LIFT HIGHER LATE IN THE
AFTERNOON TO MVFR, BUT LIKELY WILL NOT BREAK OUT.
ALONG THE COAST AND JUST OFFSHORE. VFR CONDITIONS ARE LIKELY THROUGH
EARLY THIS EVENING WITH LOWER FLIGHT CONDITIONS ARE LIKELY TO RETURN
TONIGHT.
EAST OF THE CASCADES, FREEZING FOG IS CONFINED TO PORTIONS OF
KLAMATH BASIN, INCLUDING KLAMATH FALLS, BUT SATELLITE AND WEB CAMS
SUGGEST THE FREEZING FOG AND VERTICAL VISIBILITY ARE SHALLOW AND IT
COULD CLEAR OUT WITHIN THE NEXT HOUR OR TWO, WITH VFR CONDITIONS THE
REST OF THE DAY. GUIDANCE SUGGEST FREEZING FOG AND LOW VERTICAL
VISIBILITY COULD DEVELOP AGAIN LATE THIS EVENING AND LAST FOR THE
REST OF THE TAF PERIOD. -PETRUCELLI
MARINE...UPDATED 100 PM PST FRIDAY, DECEMBER 12, 2025
LIGHT TO
MODERATE NORTH WINDS AND A MODERATE WEST SWELL WILL PERSIST THROUGH
TONIGHT. WINDS GRADUALLY SHIFT TO SOUTHERLY ON SATURDAY THEN
INCREASE AS THE DAY PROGRESSES ON SUNDAY. CONDITIONS ARE LIKELY TO
REMAIN BELOW ADVISORY CRITERIA THROUGH SUNDAY AFTERNOON, BUT A BRIEF
PERIOD OF STEEP SEAS IS POSSIBLE NORTH OF CAPE ARAGO EARLY SUNDAY.
WORSENING CONDITIONS ARE EXPECTED EARLY NEXT WEEK AS LOW PRESSURE
DEEPENS OVER THE NORTH PACIFIC AND A COLD FRONT SWINGS THROUGH THE
WATERS SUNDAY NIGHT INTO MONDAY. MORE WIDESPREAD ADVISORY LEVEL
CONDITIONS ARE EXPECTED TO RETURN LATE SUNDAY INTO MONDAY, WITH A
HIGH PROBABILITY OF GALES (>70%) AND A PERIOD OF STEEP TO VERY STEEP
HAZARDOUS SEAS LIKELY BY EARLY MONDAY MORNING. ADDITIONAL FRONTAL
SYSTEMS WILL MAINTAIN WEATHER ACTIVE WITH ELEVATED WINDS AND SEAS
THROUGH MUCH OF NEXT WEEK. /BR-Y
MFR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
CA...NONE.
PACIFIC COASTAL WATERS...NONE.
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