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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