619
FXUS66 KMFR 112226
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
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
AVIATION...11/18Z TAFS
WE HAVE REACHED THE TIME OF YEAR WHERE THE
LOW SUN ANGLE IS A SIGNIFICANT FACTOR IN THE SUSTAINABILITY OF LOW
CLOUDS/FOG IN THE VALLEYS WEST OF THE CASCADES. MUCH LIKE YESTERDAY,
STRONG HIGH PRESSURE IS IN CONTROL AND SATELLITE IMAGERY IS SHOWING
PLENTY OF LOW-LEVEL MOISTURE WITH STRATUS/FOG IN JUST ABOUT EVERY
INLAND VALLEY BELOW 2500 FEET. MOISTURE IS DEEPER FARTHER NORTH
(ROSEBURG), SO IT IS MAINLY AN MVFR CEILING THERE, BUT THERE IS ALSO
SOME LOW-LEVEL WIND (FROM THE EAST) THAT CAN BE SEEN BREAKING UP THE
STRATUS IN THE LATEST IMAGERY. WE THINK IT WILL BREAK OUT TO A
SCATTERED STRATOCUMULUS DECK THERE (ROSEBURG) THIS AFTERNOON, AT
LEAST FOR A FEW HOURS. FARTHER SOUTH, THE CEILING IS IFR AT MEDFORD
AND ISN'T SHOWING SIGNS OF BREAKING ANY TIME SOON. WE'LL MAINTAIN
THE STRATUS THROUGH THE TAF PERIOD THERE, PERHAPS WITH SLIGHT RISE
TO LOW MVFR THIS AFTERNOON. VALLEYS SOUTH OF THE SISKIYOUS
(SHASTA/SCOTT/KLAMATH) SHOULD SEE SOME EROSION OF THE FOG, BUT IT
PROBABLY WON'T GO AWAY COMPLETELY. ELSEWHERE, EAST SIDE AREAS ARE
VFR (INCLUDING KLAMATH FALLS) AND SHOULD REMAIN THAT WAY THROUGH
THE TAF PERIOD. SOME MVFR AT THE COAST NORTH OF CAPE BLANCO BREAKS
UP THIS AFTERNOON.
WEST SIDE VALLEY AREAS THAT BREAK FROM THE LOW CLOUDS/FOG THIS
AFTERNOON WILL LIKELY SEE THEM RETURN THIS EVENING/OVERNIGHT. SOME
AREAS WON'T BREAK AT ALL AND LOW CONDITIONS WILL PERSIST. CONDITIONS
ARE MORE LIKELY TO BE IFR/LIFR TONIGHT AS THE MOIST LAYER SHOULD BE
SOMEWHAT SHALLOWER THAN THE LAST COUPLE OF NIGHTS. -SPILDE
MARINE
MFR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
CA...NONE.
PACIFIC COASTAL WATERS...NONE.
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