955
FXUS66 KMFR 260353
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
853 PM PDT MON OCT 25 2021
DISCUSSION
NOT MUCH TO CHANGE IN THE FORECAST THIS EVENING. A
SHORTWAVE TROUGH WILL PASS OVERHEAD KEEPING SHOWERS GOING THIS
EVENING AND THROUGH THE OVERNIGHT HOURS, FOCUSED MAINLY ALONG AND
WEST OF THE CASCADES, THOUGH ISOLATED LIGHT RAIN/SNOW SHOWERS
COULD MAKE IT TO THE EAST SIDE AT TIMES. SNOW LEVELS ARE AROUND
5000 FEET AND THIS WILL RESULT IN SOME MOSTLY LIGHT SNOW
ACCUMULATIONS OVER THE HIGHER CASCADES, GENERALLY 2-6 INCHES
ABOVE 5500 FEET THROUGH TUESDAY MORNING. A TRACE TO 2 INCHES COULD
OCCUR ON THE PASS NEAR LAKE OF THE WOODS AND ALSO NEAR DIAMOND
LAKE WITH TEMPERATURES IN THE 32-34 DEGREE RANGE, SO BE AWARE OF
SLIPPERY ROADS IF TRAVELING OVER HIGHWAY 140 OR HIGHWAYS 230/138
IN THOSE AREAS. MOIST ONSHORE FLOW WILL CONTINUE TUESDAY AS A
WARM FRONT MOVES ONSHORE. THIS WILL RESULT IN MORE RAIN ALONG AND
WEST OF THE CASCADES WITH PRECIPITATION CHANCES DIMINISHING, BUT
NOT NEGLIGIBLE OVER THE EAST SIDE. PRECIP WILL BE ENHANCED IN THE
COAST RANGES AND OVER THE CASCADES. THESE AREAS ARE
OROGRAPHICALLY FAVORED IN THE MORE WEST-SOUTHWEST 850-700MB FLOW,
WHILE DOWNSLOPE WILL HAVE A TENDENCY TO CUT PRECIPITATION AMOUNTS
SUBSTANTIALLY IN THE WEST SIDE VALLEYS. WHERE 0.50-2.00 INCHES OF
LIQUID PRECIPITATION IS LIKELY TO OCCUR IN THE MOUNTAINS/COAST
RANGES, AMOUNTS OF 0.10 OF AN INCH OR LESS WILL BE COMMON IN THE
VALLEYS. -SPILDE
AVIATION...26/00Z TAFS
AN UPPER TROUGH WILL SWING THROUGH THE
AREA TONIGHT WITH SHOWERS, MOST NUMEROUS ALONG AND WEST OF THE
CASCADES. OVERALL, EXPECT A MIX OF VFR AND MVFR CEILINGS WITH
SOME HIGHER TERRAIN OBSCURED THIS EVENING WITH CONDITIONS GENERALLY
DETERIORATING OVERNIGHT WITH LOWER CEILINGS AND PERHAPS AREAS OF
FOG DEVELOPING IN SOME VALLEYS. A WARM FRONT WILL MOVE IN TUESDAY
WITH SOME LIGHT RAIN, AGAIN, MAINLY FOCUSED ALONG AND WEST OF THE
CASCADES. CEILINGS WILL LARGELY BE MVFR, ESPECIALLY AT THE COAST
AND IN THE UMPQUA BASIN WITH AREAS OF HIGHER TERRAIN OBSCURED, BUT
DO EXPECT IMPROVING CONDITIONS TO VFR SOUTH AND EAST OF THOSE
AREAS IN THE AFTERNOON. -SPILDE
MARINE...UPDATED 830 PM PDT MONDAY 25 OCTOBER 2021
VERY HEAVY,
LONG PERIOD SWELL WILL PERSIST THROUGH TONIGHT AND GRADUALLY SUBSIDE
TUESDAY INTO WEDNESDAY. VERY STEEP AND HAZARDOUS, WARNING LEVEL SEAS
WILL CONTINUE THROUGH TUESDAY AFTERNOON UNTIL THIS SWELL SUBSIDES. IN
THE MEANTIME, BAR CROSSINGS WILL REMAIN TREACHEROUS. A QUICK MOVING
FRONT WILL PASS THROUGH THE REGION EARLY TUESDAY MORNING, BRINGING
ANOTHER ROUND OF SOUTHERLY GALES FROM ROUGHLY GOLD BEACH NORTHWARD
AND WITHIN 40 NM FROM SHORE. BEHIND THIS FRONT, SEAS WILL CONTINUE
TO SUBSIDE TUESDAY AFTERNOON INTO WEDNESDAY, THOUGH SEAS WILL REMAIN
STEEP AND SWELL DOMINATED THROUGH AT LEAST THURSDAY MORNING. ACTIVE
WEATHER WILL PERSIST THROUGH THE REMAINDER OF THE WEEK, BUT WEATHER
FRONTS WILL BE CONSIDERABLY WEAKER THAN THEY WERE THIS PAST
WEEKEND.
PREV DISCUSSION
/ISSUED 518 PM PDT MON OCT 25 2021/
SHORT TERM... THROUGH WEDNESDAY NIGHT...WITH INCREASING
TEMPERATURES LAPSE RATES HAVE ALSO INCREASED, AND WITH THAT SHOWER
ACTIVITY IS INCREASING ALSO. WITH A COLD POOL OF -25 C AT 500 MB
THERE IS SLIGHT INSTABILITY EXTENDING FROM THE SACRAMENTO VALLEY,
WHERE A THUNDERSTORM IS CURRENTLY ACTIVE TO THE SOUTH OFTHE
FORECAST AREA, UP TO THE EAST SIDE. WITH CUMULUS DEVELOPING AT
THIS TIME HAVE ADDED A SLIGHT CHANCE OF THUNDERSTORMS TO THIS
AREA FOR LATE THIS AFTERNOON.
SHOWERS CONTINUE AHEAD OF THE NEXT FRONT THAT MOVES THROUGH
TUESDAY, THE UPPER LEVEL DYNAMICS ARE MUCH WEAK WITH THIS FRONT
THAN THIS PAST WEEKEND, AND WITH MODERATE WESTERLY FLOW AT RIDGE
LEVELS OROGRAPHICS WILL PLAY A LARGER ROLE, WITH THE HEAVIEST
PRECIPITATION AMOUNTS AT THE COAST AND COASTAL RANGE, AND THE
CASCADES. WITH THE NORTHWESTERLY JET AND THE WESTERLY RIDGE WINDS
THIS SYSTEM WILL START WITH LOWER SNOW LEVELS, REACHING DOWN TO
THE CASCADES PASSES FROM THE CRATER LAKE REGION AND NORTH, WITH A
LITTLE UNDER TWO INCHES OR LESS OF SHOW EVERY SIX HOURS THROUGH
TUESDAY AFTERNOON.
AS A WEAK UPPER RIDGE BEGINS TO BUILD LATER ON WEDNESDAY ANOTHER
WEAK FRONT MOVES OVER THE TOP WITH THE TAIL END OF THE FRONT
BRUSHES THROUGH, BRINGING ANOTHER ROUND OF WEAKER SHOWERS, MOSTLY
TO THE NORTHWEST THIRD OF THE FORECAST AREA, BUT SOME SHOWERS ARE
POSSIBLE IN FAR WESTERN SISKIYOU COUNTY. SVEN
LONG TERM...THURSDAY THROUGH MONDAY...A RIDGE OF HIGH PRESSURE
WILL HAVE NUDGED NORTHWARD FROM THE SOUTH. THIS RIDGE WILL ALSO BE
COMPETING WITH THE NEXT SYSTEM TO BRING PRECIPITATION TO THE PACIFIC
NORTHWEST. THE MAIN QUESTIONS WITH THIS PATTERN WILL BE HOW FAR
NORTH THE RIDGE BUILDS, AND THUS WHERE THE BULK OF THE PRECIPITATION
WILL LAND. FOR NOW, ENSEMBLES AND THEIR OPERATIONAL DETERMINISTIC
COUNTERPARTS SHOW THAT THE BULK OF THE PRECIPITATION ASSOCIATED WITH
THIS ATMOSPHERIC RIVER WILL MOVE INTO WASHINGTON STATE, LEAVING US
ON THE SOUTHERN PERIPHERY. ALTHOUGH WE WILL HOLD ONTO THE SOME LIGHT
PRECIPITATION CHANCES LARGELY ACROSS THE COAST, COAST RANGE, AND IN
THE UMPQUA BASIN; THIS RAINFALL WOULD BE EXTREMELY LIGHT WITH VERY
HIGH SNOW LEVELS (AROUND 10,000 FEET).
THIS SYSTEM, HOWEVER, WILL PUSH THE RIDGE EASTWARD AWAY FROM OUR
AREA AS THE FRONT SINKS SOUTHWARD OVER THE NEXT COUPLE OF DAYS
(THROUGH FRIDAY). THIS COULD BRING US SOME ADDITIONAL PRECIPITATION,
EVEN TO AREAS EAST OF THE CASCADES. HOWEVER, THE FRONT WILL LOSE
SOME ENERGY PUSHING THE RIDGE EASTWARD, SO EXPECT PRECIPITATION TO
BE RELATIVELY LIGHT. MEANWHILE, AT THE SOUTHERN EDGE OF THE FRONT,
AN AREA OF LOW PRESSURE WILL CUT OFF AND DEVELOP. THIS LOW WILL PUSH
INLAND, BRINGING ADDITIONAL PRECIPITATION CHANCES NEAR THE AREA
WHERE IT MAKES "LANDFALL", BUT ENSEMBLES ARE RELATIVELY SPLIT AS TO
THE LOCATION OF THIS LOW WITH ECMWF ENSEMBLES KEEPING A MORE
NORTHERLY TRACK GIVING US MORE NEEDED PRECIPITATION AND THE GEFS
BRINGS A MORE SOUTHERLY TRACK GIVING THE NEEDED PRECIPITATION TO
CENTRAL AND NORTHERN CALIFORNIA. MODELS WILL UNDOUBTEDLY SHOW
SIGNIFICANT CHANGES BETWEEN NOW AND ITS LANDFALL WHICH IS FORECAST
FOR SATURDAY NIGHT INTO SUNDAY. SO THIS WILL NEED TO BE TRACKED.
HAVE GONE WITH THE NATIONAL BLEND OF MODELS FOR THE EXTENDED
FORECAST AS IT SEEMS TO HAVE A DECENT BALANCE.
OVERALL, THE FORECAST WHILE REMAINING RELATIVELY ACTIVE WILL BE
LIGHT ON IMPACTS DUE TO THE LIGHT NATURE OF PRECIPITATION AND
RELATIVELY HIGH SNOW LEVELS. -SCHAAF
AVIATION...26/00Z TAFS...AN UPPER TROUGH WILL SWING THROUGH THE
AREA TONIGHT WITH SHOWERS, MOST NUMEROUS ALONG AND WEST OF THE
CASCADES. OVERALL, EXPECT A MIX OF VFR AND MVFR CEILINGS WITH
SOME HIGHER TERRAIN OBSCURED THIS EVENING WITH CONDITIONS GENERALLY
DETERIORATING OVERNIGHT WITH LOWER CEILINGS AND PERHAPS AREAS OF
FOG DEVELOPING IN SOME VALLEYS. A WARM FRONT WILL MOVE IN TUESDAY
WITH SOME LIGHT RAIN, AGAIN, MAINLY FOCUSED ALONG AND WEST OF THE
CASCADES. CEILINGS WILL LARGELY BE MVFR, ESPECIALLY AT THE COAST
AND IN THE UMPQUA BASIN WITH AREAS OF HIGHER TERRAIN OBSCURED, BUT
DO EXPECT IMPROVING CONDITIONS TO VFR SOUTH AND EAST OF THOSE
AREAS IN THE AFTERNOON. -SPILDE
MARINE...UPDATED 130 PM PDT MONDAY 25 OCTOBER 2021...VERY HEAVY,
LONG PERIOD SWELL WILL PERSIST THROUGH TONIGHT AND GRADUALLY SUBSIDE
TUESDAY INTO WEDNESDAY. VERY STEEP AND HAZARDOUS, WARNING LEVEL SEAS
WILL CONTINUE THROUGH TUESDAY AFTERNOON UNTIL THIS SWELL SUBSIDES. IN
THE MEANTIME, BAR CROSSINGS WILL REMAIN TREACHEROUS. A QUICK MOVING
FRONT WILL PASS THROUGH THE REGION EARLY TUESDAY MORNING, BRINGING
ANOTHER ROUND OF SOUTHERLY GALES FROM ROUGHLY GOLD BEACH NORTHWARD
AND WITHIN 40 NM FROM SHORE. BEHIND THIS FRONT, SEAS WILL CONTINUE
TO SUBSIDE TUESDAY AFTERNOON INTO WEDNESDAY, THOUGH SEAS WILL REMAIN
STEEP AND SWELL DOMINATED THROUGH AT LEAST THURSDAY MORNING. ACTIVE
WEATHER WILL PERSIST THROUGH THE WEEK, THOUGH SYSTEMS WILL BE
CONSIDERABLY WEAKER COMPARED TO RECENT EVENTS. /BR-Y
BEACH HAZARDS...UPDATED 200 PM PDT MONDAY 25 OCTOBER 2021...BEACHES
AND COASTLINES WILL REMAIN HAZARDOUS AS A VERY LARGE AND LONG PERIOD
SWELL CONTINUES TO BRING BREAKING WAVE HEIGHTS OF 25 TO 30 FEET
THROUGH LATE TONIGHT. WAVES WILL INUNDATE BEACHES AND SURGE INTO
NORMALLY DRY AREAS. STAY OFF OF BEACHES, ROCKS, JETTIES, AND PIERS.
THESE ARE NOT SAFE PLACES TO BE. INFRASTRUCTURE DAMAGE AND
SIGNIFICANT BEACH EROSION CAN BE EXPECTED.
MFR WATCHES/WARNINGS/ADVISORIES
OR...HIGH SURF WARNING UNTIL 5 AM PDT TUESDAY FOR ORZ021-022.
CA...NONE.
PACIFIC COASTAL WATERS...
SMALL CRAFT ADVISORY FROM 2 PM TUESDAY TO 5 PM PDT THURSDAY FOR
PZZ350-356-370-376.
GALE WARNING FROM 5 AM TO 2 PM PDT TUESDAY FOR
PZZ350-356-370-376.
HAZARDOUS SEAS WARNING UNTIL 2 PM PDT TUESDAY FOR
PZZ350-356-370-376.
MAS/MAS/MAS
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