Storm Watch 6, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
939 AM PST WED DEC 16 2015

.DISCUSSION...UPDATE THIS MORNING CONSISTS OF UPGRADING THE FLOOD
WATCH FOR THE SOUTH FORK OF THE COQUILLE RIVER AT MYRTLE POINT TO
A FLOOD WARNING...KEEPING THE FLOOD WATCH FOR THE NORTH FORK OF
THE COQUILLE RIVER AT MYRTLE POINT AS IS. WE ALSO ISSUED A WINTER
STORM WARNING FOR HEAVY SNOW FOR AREAS FROM AROUND DIAMOND LAKE
JUNCTION NORTH INTO CHEMULT...AND WINTER WEATHER ADVISORY FOR THE
REST OF KLAMATH AND LAKE COUNTY...DOWN INTO THE TULELAKE AREA OF
SISKIYOU COUNTY. HAVE DECIDED TO REMOVE MODOC COUNTY FROM THE
WATCH AS SNOW AMOUNTS ARE EXPECTED TO STAY BELOW ADVISORY
CRITERIA. /FB

&&

.MARINE...UPDATED 240 AM PST WEDNESDAY 16 DEC 2015...LONG PERIOD
NORTHWEST SWELL WILL PRODUCE SEAS HAZARDOUS TO SMALL CRAFT
THROUGH WEDNESDAY. MODERATE SWELL WILL BECOME WESTERLY WEDNESDAY
NIGHT...AND SEAS WILL BECOME CHOPPY AS SOUTH WINDS INCREASE TO
AROUND GALE FORCE WITH A STRONG WARM FRONT. A COLD FRONT WILL MOVE
THROUGH THURSDAY. A STRONGER COLD FRONT WILL MOVE THROUGH THURSDAY
NIGHT INTO FRIDAY...BRINGING ANOTHER ROUND OF STRONG SOUTH WINDS.
HEAVY WEST TO NORTHWEST SWELL WILL DEVELOP FRIDAY NIGHT...PEAK
SATURDAY NIGHT...THEN GRADUALLY SUBSIDE THROUGH SUNDAY. YET
ANOTHER FRONT WILL MOVE THROUGH THE AREA SATURDAY NIGHT INTO
SUNDAY.

&&

.PREV DISCUSSION... /ISSUED 403 AM PST WED DEC 16 2015/

SHORT TERM...A QUICK-MOVING SHORTWAVE TROUGH IS MOVING THROUGH THE
FORECAST AREA THIS MORNING...BRINGING SOME RAIN TO MAINLY THE
NORTHERN PORTIONS OF THE FORECAST AREA...TO INCLUDE COOS AND
DOUGLAS COUNTIES. PRECIPITATION WILL DIMINISH FROM THIS WEAK
SYSTEM THIS MORNING. THEN...ATTENTION SHIFTS TO A WARM FRONTAL
BOUNDARY THAT WILL USHER IN MODERATE TO HEAVY COASTAL AND MOUNTAIN
PRECIPITATION LATE TODAY THROUGH THURSDAY. STRONG WEST WINDS WILL
IMPINGE UPON THE COAST RANGE AND CASCADES TONIGHT...AND SHOULD
ENHANCE PRECIPITATION IN THOSE AREAS. WE HAVE ISSUED A WINTER
WEATHER ADVISORY AT WSWMFR FOR THE CASCADES TONIGHT INTO THURSDAY
MORNING. SNOWFALL RATES COULD BE BRIEFLY VERY HIGH...AND GIVEN THE
RECENT SNOW LOADING ON TREES AND POTENTIAL FOR GUSTY WINDS
ACCOMPANYING AND FOLLOWING THE SNOW...IMPACT WAS DEEMED
SIGNIFICANT ENOUGH FOR AN ADVISORY ABOVE 5000 FEET. SNOW LEVELS
SHOULD RISE TO ABOUT 7000 BY LATE THURSDAY MORNING. SNOW WILL
AFFECT ELEVATIONS ABOVE 4000 FEET INITIALL LATE THIS AFTERNOON AND
EVENING BUT SHOULD CHANGE TO RAIN BEFORE SIGNIFICANT IMPACTS
OCCUR. ADDITIONALLY...ROAD SURFACE TEMPERATURES SHOULD BE ABOVE
FREEZING IN AREAS LIKE SISKIYOU SUMMIT WHEN SNOW ARRIVES LATE THIS
AFTERNOON...AND MELTING SHOULD OCCUR.

ON THE EAST SIDE...A WINTER STORM WATCH AT WSWMFR REMAINS FOR THE
POTENTIAL FOR SNOW AND FREEZING RAIN. MODELS ARE IN FAIRLY GOOD
AGREEMENT ON THE EVOLUTION OF THE WEATHER EAST OF THE
CASCADES...WITH SNOW FIRST EXPECTED THURSDAY MORNING...THEN CHANGING
TO FREEZING RAIN THEN RAIN IN PLACES LIKE KLAMATH FALLS AND TULE
LAKE. FURTHER NORTH...AREAS LIKE CHEMULT MAY MAKE A QUICKER
TRANSITION FROM SNOW TO RAIN BUT COULD HAVE A BRIEF PERIOD OF HEAVY
SNOW THURSDAY MORNING. FARTHER EAST...WINTRY PRECIPITATION SHOULD BE
LIGHTER BUT MAY NOT CHANGE TO RAIN AT ALL AS COLD AIR REMAINS
ENTRENCHED IN PLACES LIKE LAKEVIEW AND ALTURAS. HAVE ADJUSTED SNOW
LEVELS DOWN IN THESE AREAS. ANOTHER LOCATION THAT MAY EXPERIENCE
FREEZING RAIN IS MOUNT SHASTA CITY. ITS HARD TO IGNORE THE NAM12
FORECAST SOUNDING THAT SHOWS A CLEAR WARM LAYER ABOVE FREEZING
SURFACE TEMPERATURES. HOWEVER...MOS GUIDANCE SUGGESTS MOUNT SHASTA
SURFACE TEMPERATURES WILL BE ABOVE FREEZING. WE HAVE ADDED A SLIGHT
CHANCE OF FREEZING RAIN IN THIS AREA FOR THURSDAY MORNING.

AT THE COAST...RAINFALL WILL FURTHER SWELL RIVERS...AND FLOOD
WATCHES FOR THE NORTH AND SOUTH FORKS OF THE COQUILLE HAVE BEEN
ISSUED. ADDITIONALLY...THE COQUILLE RIVER AT COQUILLE IS STILL AT
FLOOD STAGE AND WILL START RISING AGAIN WITH THE UPCOMING
PRECIPITATION. TOTAL RAIN AMOUNTS AT THE COAST THROUGH FRIDAY ARE 4
TO 7 INCHES. OF NOTE IS THE CONSISTENCY OF THE RECENT EC AND GFS
MODEL RUNS...MAINTAINING THE SAME GENERAL IDEA OF QPF AMOUNTS. GUSTY
WINDS WILL IMPACT THE COAST AS THE COLD FRONT PUSHES ONSHORE
THURSDAY NIGHT. GUIDANCE SUGGESTS JUST BELOW HIGH WIND CRITERIA NOW
BUT WILL NEED TO EXAMINE FUTURE GUIDANCE FOR THE POTENTIAL OF A HIGH
WIND WATCH.

LONG TERM...SATURDAY THROUGH TUESDAY NIGHT...SHOWERS WITH SNOW
LEVELS BETWEEN 2500 AND 3500 FEET ON SATURDAY WILL TRANSITION INTO
MORE STEADY PRECIPITATION BY SUNDAY. MODEL GUIDANCE IS VARIED ON
AMOUNT AND SNOW LEVEL DETAILS WITH THIS FRONT, BUT IT DOES APPEAR
THAT, YET AGAIN, IMPACTS ARE EXPECTED ON THE MOUNTAIN PASSES ABOVE
3500 FEET, AND THEY COULD BE SIGNIFICANT.

MONDAY THROUGH WEDNESDAY ADDITIONAL FRONTAL WAVES ROLL INTO THE
FORECAST AREA WITH SNOW LEVELS RISING AS HIGH AS 5500-6500 FEET
EARLY TUESDAY AND AS LOW AS 3000 FEET ON THE FRONT AND TAIL ENDS OF
THIS TIME PERIOD. THOSE PLANNING TO TRAVEL OVER THE MOUNTAIN PASSES
DURING THIS TIME PERIOD WILL NEED TO PAY CLOSE ATTENTION TO THE
FORECAST, AS TIMING OF SNOW LEVEL TRANSITIONS AND PRECIPITATION
COULD CHANGE. ADDITIONALLY, SOME MODEL GUIDANCE SUGGESTS A SURGE OF
MOISTURE SUNDAY THROUGH WEDNESDAY SIGNIFICANT ENOUGH TO CAUSE OR
CONTINUE RIVER FLOODING CONDITIONS FROM THE CASCADES WESTWARD.
INDEED, THIS IS SETTING UP TO BE A VERY WET DECEMBER AND WITH A
STRONG SNOW PACK IN THE MOUNTAINS. BTL

AVIATION...FOR THE 16/12Z TAF CYCLE...AREAS OF IFR CIGS OVER THE
VALLEYS WILL PERSIST THROUGH MID-MORNING...THEN CLEAR TO VFR. THE
REMAINDER OF THE AREA WILL REMAIN VFR THROUGH THIS MORNING. A
WARM FRONT WILL BRING AREAS OF MVFR CIGS/VSBYS TO THE AREA THIS
AFTERNOON INTO TONIGHT WITH HIGHER TERRAIN BECOMING OBSCURED.
AREAS OF FREEZING PRECIPITATION WILL DEVELOP TONIGHT EAST OF THE
CASCADES.

MARINE...UPDATED 240 AM PST WEDNESDAY 16 DEC 2015...LONG PERIOD
NORTHWEST SWELL WILL PRODUCE SEAS HAZARDOUS TO SMALL CRAFT
THROUGH TODAY. MODERATE SWELL WILL BECOME WESTERLY TONIGHT...AND
SEAS WILL BECOME CHOPPY AS SOUTH WINDS INCREASE TO AROUND GALE
FORCE WITH A STRONG WARM FRONT. A COLD FRONT WILL MOVE THROUGH
THURSDAY. A STRONGER COLD FRONT WILL MOVE THROUGH THURSDAY NIGHT
INTO FRIDAY...BRINGING ANOTHER ROUND OF STRONG SOUTH WINDS. HEAVY
WEST TO NORTHWEST SWELL WILL DEVELOP FRIDAY NIGHT...PEAK SATURDAY
NIGHT...THEN GRADUALLY SUBSIDE THROUGH SUNDAY. YET ANOTHER FRONT
WILL MOVE THROUGH THE AREA SATURDAY NIGHT INTO SUNDAY.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO NOON PST
     THURSDAY FOR ORZ030.
     WINTER STORM WARNING FROM 10 PM THIS EVENING TO 10 AM PST
     THURSDAY FOR ORZ029-030.
     WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO NOON PST
     THURSDAY FOR ORZ029-031.
     WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 10 AM PST
     THURSDAY FOR ORZ027-028.

CA...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO NOON PST
     THURSDAY FOR CAZ084.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 10 PM PST
     THURSDAY FOR PZZ350-356-370-376.
     GALE WARNING FROM 6 PM THIS EVENING TO 2 AM PST THURSDAY FOR
     PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 PM PST THIS
     EVENING FOR PZZ350-356-370-376.

FJB/BTL/BTL