327
FXUS66 KMFR 120528
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
928 PM PST THU DEC 11 2025
UPDATE
AVIATION DISCUSSION UPDATED.
AVIATION...12/06Z TAFS
MUCH LIKE YESTERDAY, STRONG HIGH PRESSURE
IS IN CONTROL AND LOW LEVEL MOISTURE IS PERSISTING IN VALLEYS. 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 AS WELL AS PATCHY
FOG IN THE UMPQUA AND COQUILLE VALLEYS. OVERNIGHT, EXPECT CEILINGS
AND VISIBILITIES TO LOWER IN THE ROGUE VALLEY, DOWN TO LIFR
CONDITIONS. ELSEWHERE IN VALLEYS WEST OF THE CASCADES,
EXPECT LIFR/IFR CONDITIONS TO BECOME WIDESPREAD. THESE CONDITIONS
WILL PERSIST THROUGH FRIDAY MORNING AND FOR SOME AREAS, SUCH AS
MEDFORD, ARE EXPECTED TO SEE LOW CLOUDS INTO THE AFTERNOON ON
FRIDAY. ALONG THE COAST, AREAS OF FOG WITH IFR/LIFR ARE PRESENT
(INCLUDING AT NORTH BEND). THESE CONDITIONS WILL PERSIST INTO FRIDAY
MORNING, BEFORE LIFTING TO VFR. EAST OF THE CASCADES, EXPECT MAINLY
VFR THROUGH THE TAF PERIOD.
PREV DISCUSSION
/ISSUED 439 PM PST THU DEC 11 2025/
MARINE...UPDATED 100 PM PST THURSDAY, DECEMBER 11, 2025...LONG
PERIOD WNW SWELL IS CAUSING SEAS ABOUT 8-10 FEET CURRENTLY, BUT
CONDITIONS SHOULD IMPROVE THE REST OF THIS AFTERNOON INTO SATURDAY
AS HIGH PRESSURE BUILDS AND SEAS SUBSIDE. MOSTLY LIGHT TO
MODERATE NORTH WINDS CAN BE EXPECTED TONIGHT THROUGH FRIDAY NIGHT.
GRADUALLY, WINDS SHIFT TO SOUTHERLY SATURDAY AND INCREASE INTO
SUNDAY, BUT STILL PROBABLY REMAIN BELOW SMALL CRAFT ADVISORY
LEVELS.
LOW PRESSURE THEN DEEPENS OVER THE NORTH PACIFIC AND A COLD FRONT
WILL SWING THROUGH THE WATERS SUNDAY NIGHT INTO MONDAY. THIS WILL
BRING A HIGH PROBABILITY OF GALES (>70%) AND A PERIOD OF STEEP TO
VERY STEEP HAZARDOUS SEAS. A SERIES OF FRONTAL SYSTEMS IS LIKELY
TO KEEP THE WEATHER ACTIVE WITH ELEVATED WINDS AND SEAS MUCH OF
NEXT WEEK. -SPILDE
PREV DISCUSSION... /ISSUED 226 PM PST THU DEC 11 2025/
DISCUSSION...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 POSSIBLE IT WILL REMAIN SOCKED IN THE 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 FRIDAY MORNING.
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 FRIDAY 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 FRIDAY 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.
BASICALLY 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 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, MOUNTAINS SNOW AND MODERATE TO OCCASIONALLY STRONG WINDS.
THE MAIN ISSUE WILL BE THE TIMING OF EACH INDIVIDUAL SYSTEM WHICH IS
LIKELY TO VARY IN THE DAYS TO COME.
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.
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
THE LAST COUPLE OF WEEKS. IN OTHER WORDS, THE SWITCH BASICALLY
GETS FLIPPED AS THE OVERALL PATTERN CHANGES. -PETRUCELLI
MFR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
CA...DENSE FOG ADVISORY UNTIL 9 AM PST FRIDAY FOR CAZ081.
PACIFIC COASTAL WATERS...NONE.
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