821
FXUS66 KMFR 202243
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
243 PM PST THU FEB 20 2025
DISCUSSION
CEILINGS PERSISTED INTO THE AFTERNOON IN VALLEYS AND
BASINS ACROSS NORTHERN CALIFORNIA AND SOUTHERN OREGON, BUT HAS
EITHER CLEARED OUT OR AT LEAST PARTIALLY BROKEN UP AS OF WRITING
THIS FORECAST. THIS WILL ALLOW FOR THE SURFACE TO WARM, WHICH WILL
THEN SUPPORT CHANCES FOR FOG TO DEVELOP IN THESE AREAS ONCE AGAIN ON
FRIDAY MORNING. WORKING AGAINST THESE CONDITIONS IS THAT A WEAK
UPPER RIDGE IS BEING PUSHED TO THE EAST, CHANGING SURFACE FLOW FROM
EASTERLY TO SOUTHERLY. WINDS FROM THE SOUTH HAVE A BETTER CHANCE OF
GETTING INTO VALLEYS AND MIXING THE AIR A BIT. HOWEVER, THESE
SOUTHERLY WINDS ARE LIGHT AND MAY NOT PROVIDE SUFFICIENT MIXING TO
FULLY PREVENT DEVELOPMENT. FOG IS EXPECTED TO RETURN TO THESE AREAS
TONIGHT INTO FRIDAY MORNING, BUT MAY REMAIN PATCHY OVERNIGHT AND
CLEAR EARLIER IN THE MORNING.
FRIDAY LOOKS TO REMAIN LARGELY UNEVENTFUL AS THE WEAK UPPER RIDGE
FLATTENS, ALLOWING A WEAK FRONT TO APPROACH THE OREGON COAST LATE
FRIDAY NIGHT INTO SATURDAY. THIS FIRST FRONT WILL BE UNIMPACTFUL,
BRINGING SOME SHOWERS OVER THE COAST AND OVER HIGHER TERRAIN WEST OF
AND ALONG THE CASCADES. IN GENERAL, AREAS THAT MANAGE TO GET RAIN
WILL GET 0.1 INCHES OR LESS FROM FRIDAY AFTERNOON TO SATURDAY
MORNING.
SUSTAINED ACTIVITY LOOKS POSSIBLE FROM SATURDAY AFTERNOON TO TUESDAY
MORNING AS AN ATMOSPHERIC RIVER COULD SET UP AND BRING STEADY
MOISTURE OVER THE AREA. IN THIS TIMEFRAME, SATURDAY AFTERNOON-SUNDAY
MORNING AND MONDAY EVENING-TUESDAY MORNING WILL BE PERIODS OF
INTEREST AS FRONTS ARE EXPECTED TO SUPPORT ADDITIONAL LIFTING AND
BRING MORE ACTIVITY.
THE SATURDAY FRONT LOOKS TO BE THE WETTEST PERIOD, WITH AREAS SOUTH
OF CAPE BLANCO FORECAST TO GET 2 TO 3 INCHES OF RAINFALL AND AREAS
TO THE NORTH GETTING 1 TO 1.5 INCHES. SNOW LEVELS OF 8000 FEET OR
HIGHER MAKE SNOWFALL A NON-ISSUE FOR THIS FIRST FRONT. GUSTY WINDS
COULD DEVELOP ALONG THE OREGON COAST AND OVER ELEVATED TERRAIN.
CURRENT GUIDANCE SHOWS THESE WINDS SAFELY OUT OF ADVISORY LEVELS,
BUT THIS WILL BE WATCHED CLOSELY IN FUTURE FORECASTS.
FROM SUNDAY MORNING TO MONDAY MORNING, SHOWERS CONTINUE WITH UPSLOPE
FLOW BEING THE MAIN LIFTING MECHANISM. THE OREGON COAST WILL STILL
SEE THE MOST RAINFALL IN THIS PERIOD, WITH ANOTHER 1 TO 1.5 INCHES
FORECAST FROM BROOKINGS TO REEDSPORT. IN GENERAL, ACTIVITY LOOKS
MORE SPORADIC IN THIS PERIOD. SNOW LEVELS REMAINING OVER 6000 FEET
WILL CONTINUE TO LIMIT SNOWFALL.
FOR THE MONDAY EVENING FRONT, MOISTURE IN THE ATMOSPHERIC RIVER WILL
BE DECREASING. WHILE THIS WILL BE THE "DRIEST" PERIOD OF THE RIVER,
SNOW LEVELS DROPPING TO 4000 FEET WITH THIS FRONT WILL MAKE ACTIVITY
OVER THE CASCADES WORTH CONSIDERING. LONG TERM METEOGRAMS FROM THE
ECMWF AND GFS BOTH SHOW A SPLIT BETWEEN CRATER LAKE GETTING EITHER 1-
2 INCHES OR 4-5 INCHES FOR MONDAY EVENING INTO TUESDAY MORNING. THIS
MIGHT GET INTERPRETED AS 3 INCHES BEING THE MOST LIKELY OUTCOME, BUT
ENSEMBLE GUIDANCE HAD FEW MEMBERS IN THE 2-4 INCH RANGE. OUTCOMES ON
THE HIGHER END ARE STILL SHORT OF ADVISORY SNOWFALL, BUT THE
DIFFERENCE BETWEEN 1 INCH AND 6 INCHES OF SNOWFALL IS WORTH PAYING
ATTENTION TO. RIGHT NOW, THE FORECAST LEANS TOWARDS THE 4-6 INCH
RANGE.
BEYOND THE ATMOSPHERIC RIVER, AN UPPER LEVEL RIDGE LOOKS TO BRING A
DRY PERIOD FROM NEXT WEDNESDAY INTO NEXT WEEKEND. WITH LINGERING
MOISTURE AT THE SURFACE, MORNING VALLEY FOG WILL BE A CONSIDERATION.
TEMPERATURES WEST OF THE CASCADES LOOK TO BE SAFELY ABOVE FREEZING,
WHILE TEMPERATURES EASTWARD ARE EXPECTED TO BE IN THE MID 20S TO LOW
30S UNDER THE RIDGE. -TAD
AVIATION...20/18Z TAFS
A MIX OF CONDITIONS EXIST ACROSS THE AREA
THIS MORNING. FOR VALLEYS WEST OF THE CASCADES AND PORTIONS OF THE
KLAMATH BASIN, LIFR/IFR CONDITIONS IN FOG/LOW CLOUDS ARE PRESENT,
BUT GRADUALLY LIFTING AND BREAKING. ALONG THE COAST AND AREAS EAST
OF THE CASCADES, PATCHY MVFR CONDITIONS ARE PRESENT IN STRATUS. NOT
MUCH CHANGE IS EXPECTED THROUGH THE MORNING HOURS, WITH CONDITIONS
IN ALL AREAS EXPECTED TO IMPROVE TO VFR BY THE AFTERNOON.
A STABILIZING AIR MASS IS EXPECTED TO RESULT IN AREAS OF MAINLY WEST
SIDE VALLEY LIFR LOW CLOUDS AND FOG LATE THIS EVENING INTO FRIDAY
MORNING. /DW
MARINE...UPDATED 200 PM PST THURSDAY, FEBRUARY 20, 2025
LIGHT TO
MODERATE NORTH WINDS AND SWELL DOMINATED SEAS CONTINUE INTO FRIDAY
MORNING. INCREASING SOUTH WINDS AND BUILDING SEAS ARE EXPECTED
FRIDAY AHEAD OF COLD FRONT WITH STEEP SWELL DOMINATED SEAS EXPECTED
FRIDAY INTO SATURDAY.
A STRONGER FRONT IS EXPECTED LATER SATURDAY WITH A GOOD CHANCE OF
SOUTH GALES SATURDAY NIGHT. THE PROBABILITY OF WIND GUSTS HIGHER
THAN 41 KNOTS IS ABOUT 80 PERCENT AND 30 PERCENT FOR HIGHER THAN
48 KNOTS. THEREFORE, WE DECIDED TO GO WITH A GALE WATCH SATURDAY
NIGHT INTO SUNDAY MORNING. HIGH AND VERY STEEP CHAOTIC SEAS ARE
LIKELY WITH THIS FRONTAL PASSAGE. THE HIGH AND STEEP SEAS WILL
PERSIST INTO SUNDAY AND MONDAY BEFORE SOME 16 TO 18 FOOT WAVES
ARRIVE ON TUESDAY.
-SMITH
MFR WATCHES/WARNINGS/ADVISORIES
OR...CA...NONE.
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FROM 4 AM FRIDAY TO 1
AM PST SUNDAY FOR PZZ356-376.
SMALL CRAFT ADVISORY FROM 4 AM FRIDAY TO 10 AM PST SATURDAY FOR
PZZ350-370.
GALE WATCH FROM SATURDAY MORNING THROUGH LATE SATURDAY NIGHT FOR
PZZ350-370.
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