323
FXUS66 KMFR 291106
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
306 AM PST MON DEC 29 2025
DISCUSSION
FORECAST CONFIDENCE REMAINS FAIRLY HIGH IN THE
OVERALL EVOLUTION OF CONDITIONS DURING THE NEXT 10 DAYS. HIGH
PRESSURE WILL REMAIN IN CONTROL THROUGH MID-WEEK, LEADING TO DRY
CONDITIONS WITH STRONG VALLEY INVERSIONS. THIS WILL RESULT IN
PERSISTENT STAGNANT AIR IN VALLEYS, AND AN AIR STAGNATION ADVISORY
REMAINS IN EFFECT FOR THE SOUTHERN OREGON VALLEYS EAST OF THE
COAST RANGE THROUGH WEDNESDAY AFTERNOON. AN ACTIVE PATTERN WILL
FOLLOW WEDNESDAY NIGHT OR THURSDAY AND PERSIST INTO AT LEAST INTO
EARLY NEXT WEEK.
A WEAK SHORTWAVE IS SWINGING SOUTHEASTWARD ACROSS OREGON THIS
MORNING, BRINGING AN INCREASE OF HIGH CLOUDS. MEANWHILE, PERSISTENT
STRATUS CONTINUES IN THE UMPQUA BASIN WITH SOME PATCHY AREAS OF
FREEZING FOG DEVELOPING IN THE ROGUE/KLAMATH RIVER/SCOTT VALLEYS.
OVERALL DAY TO DAY CONDITIONS AREN'T EXPECTED TO CHANGE MY THROUGH
WEDNESDAY, SO EXPECT THIS AFTERNOON TO SHAPE UP MUCH LIKE SUNDAY
DID.
A FEW MORE SIMILAR SHORTWAVES WILL FOLLOW DURING THE NEXT FEW DAYS
WITH SIMILARLY VERY MODEST EFFECT (INCREASE IN HIGH CLOUDS), BUT ON
A BROADER SCALE, HIGH PRESSURE WILL CONTINUE TO BUILD NORTHEAST INTO
THE REGION THROUGH TUESDAY THEN LINGER ON WEDNESDAY AS IT BEGINS TO
SHIFT EASTWARD. THE RESULT IS THAT EACH OF THE NEXT FEW DAYS WILL
INCLUDE MAINLY, BUT NOT EXCLUSIVELY, WEST SIDE NIGHT AND MORNING
VALLEY FOG AND FREEZING FOG, WEST SIDE LOWS MAINLY IN THE UPPER 20S
TO LOWER 30S, EAST SIDE LOWS MAINLY IN THE TEENS, MOSTLY CLEAR SKIES
AND SEASONABLE TEMPERATURES AT THE COAST. FOG AND FREEZING FOG WILL
HAVE THE HARDEST TIME BREAKING OUT IN JOSEPHINE AND DOUGLAS COUNTIES.
WE WILL START OUT THE FIRST HOURS OF THE NEW YEAR WITH INCREASING
CLOUDS AND AN INCREASING PROBABILITY OF LIGHT PRECIPITATION. A WARM
FRONT LIFTING NORTHWARD IS FORECAST TO RESULT IN SNOW LEVELS AROUND
6000 TO 7000 FEET. THE CENTER OF THE PARENT UPPER TROUGH IS EXPECTED
TO TRACK ACROSS CENTRAL CALIFORNIA ON THURSDAY, CONTINUING WHAT IS
LIKELY TO BECOME A BROADER COVERAGE OF LIGHT PRECIPITATION IN OUR
AREA WHILE SNOW LEVELS REMAIN HIGH.
BEYOND THURSDAY, THE FINER DETAILS OF THE STRENGTH AND TIMING OF
SYSTEMS BEGIN TO DIVERGE AMONGST THE SUITE OF MODELS. BUT, A COLDER,
STRONGER SYSTEM IS EXPECTED TO TRACK EAST-SOUTHEAST FROM THE GULF OF
ALASKA AND ACROSS OUR AREA DURING FRIDAY THROUGH SATURDAY. THIS
TRACK BRINGS THE HIGHEST PROBABILITY THAT HIGHER PRECIPITATION
AMOUNTS WILL BE FOCUSED ON THE COAST, AND WESTERN AND SOUTHERN
SISKIYOU COUNTY, SECONDARILY INTO JOSEPHINE COUNTY AND ON THE
CASCADES, WITH SNOW LEVELS IN OUR AREA DROPPING TO MORE SEASONABLY
TYPICAL VALUES OF AROUND 4000 TO 5000 FEET. THIS MAY BE A LIGHT
EVENT AWAY FROM THE COAST AND MT. SHASTA REGION, PERHAPS NOT EVEN
WARRANTING WINTER WEATHER ADVISORIES ELSEWHERE INLAND. BUT,
SOUTHERLY WINDS WILL AT LEAST BECOME BREEZY TO WINDY.
DETAILS DIVERGE FURTHER BEYOND FRIDAY, BUT ANOTHER SIMILAR SYSTEM TO
ITS IMMEDIATE PREDECESSOR IS LIKELY DURING THE WEEKEND.
AVIATION...29/12Z TAFS
OVERALL, VFR CONDITIONS PREVAIL FOR MUCH
OF THE FORECAST AREA AND WILL DO SO THROUGH THE TAF PERIOD. THERE IS
SOME HIGH LEVEL CLOUD COVER STREAMING OVER THE REGION THIS MORNING
ALONG WITH GUSTY EAST TO NORTHEAST WINDS ACROSS THE TERRAIN AND
ALONG THE COAST. IFR CONDITIONS PERSIST IN THE UMPQUA BASIN AND WILL
LIKELY DO SO THROUGH MUCH OF THE TAF PERIOD, THOUGH BRIEFLY LIFTING
TO MVFR THIS AFTERNOON. LIFR CONDITIONS ARE EXPECTED IN THE
REMAINDER OF THE WEST SIDE VALLEYS TOWARDS SUNRISE (ALREADY PRESENT
IN THE GRANTS PASS/MERLIN AREA). THESE LOWER CONDITIONS SHOULD
IMPROVE TO VFR AROUND 18-20Z TODAY, LINGERING LONGEST IN THE
ILLINOIS VALLEY.
MARINE...UPDATED 200 AM PST MONDAY, DECEMBER 29, 2025
GUSTY NORTH
ARE GRADUALLY EASING THIS MORNING AND WILL REMAIN BELOW ADVISORY
CRITERIA THROUGH THIS EVENING. STEEP SEAS WILL CONTINUE THROUGH THE
MORNING, GRADUALLY RETREATING FARTHER SOUTH AS THE MORNING
PROGRESSES. SEAS TRANSITION TO SWELL DOMINATED THIS AFTERNOON, SO
EXPECT IMPROVING CONDITIONS TODAY THAT WILL PERSIST THROUGH AT LEAST
MID-WEEK. THE WEAK THERMAL TROUGH RESPONSIBLE FOR THE NORTHERLY
WINDS WILL SHIFT NORTHWARD TONIGHT INTO TUESDAY, BRINGING A BRIEF
PERIOD OF BREEZY SOUTHERLY WINDS WITHIN 10-30 NM FROM SHORE.
STRONGER SOUTH WINDS BEGIN LATE IN THE WEEK AHEAD OF THE NEXT SERIES
OF FRONTAL SYSTEMS.
MFR WATCHES/WARNINGS/ADVISORIES
OR...SMALL CRAFT ADVISORY UNTIL 10 AM PST THIS MORNING FOR ORZ021.
AIR STAGNATION ADVISORY UNTIL 4 PM PST WEDNESDAY FOR ORZ023>026-
029>031.
CA...NONE.
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 10 AM PST THIS
MORNING FOR PZZ350-356-370-376.
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