High Wind in California, December 9 to 10, 2015

AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE MEDFORD OR
1050 PM PST WED DEC 9 2015

AVIATION AND MARINE SECTIONS HAVE BEEN UPDATED

.DISCUSSION...
NO UPDATE WILL BE ISSUED TONIGHT, AS THE GOING FORECAST AND
CURRENT HEADLINES LOOK WELL ON TRACK.

RIVER RISES CONTINUE THIS EVENING IN THE COQUILLE BASIN WITH
RIVER FORECASTS MOSTLY ON TRACK. THE COQUILLE AT COQUILLE IS
CURRENTLY RUNNING ABOUT A HALF A FOOT ABOVE THE FORECAST. WITH THE
RIVER THERE EXPECTED TO REACH ACTION STAGE THURSDAY NIGHT, IT'S
POSSIBLE IT COULD REACH ACTION STAGE LATE THURSDAY AFTERNOON IF
CURRENT TRENDS CONTINUE. RIVERS IN THE UMPQUA BASIN LOOK ON TRACK,
WITH MOST OF THEM HAVING PEAKED FROM THE LAST ROUND OF RAINFALL.

THE STRONG FRONTAL SYSTEM MOVING IN THIS EVENING THROUGH THURSDAY
IS VERY IMPRESSIVE ON SATELLITE IMAGERY, AND SOME LIGHTNING IS
OCCURRING JUST WEST OF OUR COASTAL WATERS. WINDS ARE RAPIDLY
INCREASING ALONG THE COAST, IN THE MOUNTAINS, AND IN SOUTH AND
SOUTHEAST FLOW PRONE VALLEYS TONIGHT. THESE WINDS WILL CONTINUE TO
INCREASE AS THE STRONG FRONTAL BOUNDARY NEARS.

TEMPERATURES THIS EVENING HAVE DROPPED OFF A BIT MORE THAN
EXPECTED IN SOME AREAS, WHICH YIELDS SOME PROMISE FOR SNOW LEVELS
TO END UP ON THE LOWER SIDE OF THE MODEL SPECTRUM. WHILE CURRENT
HOURLY FORECAST VALUES ARE NOT ON TRACK PER ISSUES WITH THE
HOURLY TREND TOOLS, THE FORECAST AND NET RESULTANT SNOW AMOUNTS
LOOK PRETTY GOOD. IN FACT, THE LATEST GFS20 INDICATES MORE POST
FRONTAL PRECIPITATION ON THURSDAY THAN WAS PREVIOUSLY INDICATED,
SO AM CONFIDENT THAT THE GOING WINTER WEATHER ADVISORY IS ON
TRACK WITH NOTABLE AMOUNTS.

THE FRIDAY WEATHER SYSTEM HAS ALSO TRENDED A BIT WETTER IN THE
MOUNTAINS PER THE GFS20, WITH ABOUT A HALF INCH TO AN INCH OF
WATER EXPECTED, MOSTLY IN THE FORM OF MOUNTAIN SNOW ABOVE 4KFT.

SPECIAL ATTENTION WILL CONTINUE TO BE NEEDED FOR THIS WEEKEND. A
POWERFUL, WET, AND DYNAMIC FRONTAL SYSTEM WILL PUSH INTO THE AREA
WITH A WAVE DEVELOPING ALONG THE FRONT IN OUR AREA. WHERE THE
FRONT LIES AND HOW STRONG THE WAVE IS WILL GREATLY INFLUENCE
PRECIPITATION AMOUNTS AND SNOW LEVELS. AFTER TRENDING COLDER IN
THE LAST 24 HOURS IN THE MODELS, THIS STORM SYSTEM HAS TAKEN A
WAG BACK TO A BIT WARMER FOR THE SATURDAY NIGHT TIME FRAME. THESE
DETAILS WILL BE CRITICAL TO IMMEDIATE AND LONGER TERM HYDROLOGICAL
IMPACTS. THE SHORT STORY IS THAT WATER AMOUNTS FROM THE SATURDAY-
SUNDAY SYSTEM WILL BE ON THE ORDER OF 2 TO 6 INCHES FOR THE WEST
SIDE, WITH LOCALLY UP TO 10 INCHES. AT THIS POINT IT APPEARS THE
CHETCO, ILLINOIS, ROGUE, SMITH, AND KLAMATH RIVER BASINS WILL GET
THE BRUNT OF THE PRECIPITATION, BUT, GIVEN RECENT AND EXPECTED
PRECIPITATION THE UMPQUA AND COQUILLE BASINS WILL ALSO BEAR CLOSE
WATCH. EXPECT WE WILL NEED A WINTER STORM WATCH FOR THIS
PERIOD AFTER MORE IMMEDIATE HEADLINES ARE FINISHED. BTL

&&

.AVIATION...FOR THE 10/06Z TAF CYCLE...A STRONG FRONTAL SYSTEM WILL
BRING RAIN AND MVFR CIGS TO SOUTHERN OREGON TONIGHT INTO THURSDAY.
SOUTH TO SOUTHEAST WINDS WILL INCREASE AHEAD OF THE FRONT WITH LOW
LEVEL WIND SHEAR TONIGHT AND, IN SOME LOCATIONS, INTO THURSDAY.
MOUNTAINS WILL BE OBSCURED THROUGH THE PERIOD. AS THE FRONT MOVES
THROUGH LATE TONIGHT INTO THURSDAY SNOW LEVELS WILL DROP, SO
PROBABILITIES OF ICING INCREASE. BTL

&&

.MARINE...UPDATED 830 PM PST WEDNESDAY 9 DEC 2015...A STRONG FRONTAL
SYSTEM WILL BRING SOUTHERLY GALES TONIGHT. WIND GUSTS MAY BRIEFLY
REACH STORM FORCE BEYOND 30 NM FROM SHORE LATE TONIGHT.
SEAS WILL BE DOMINATED INITIALLY BY WIND DRIVEN WAVES BUT A LARGE
WESTERLY SWELL WILL MOVE INTO THE AREA THURSDAY BEHIND THE COLD
FRONT. COMBINED SEAS WILL BUILD TO 25 TO 35 FEET THURSDAY. THESE
VERY HEAVY SEAS WILL PERSIST INTO FRIDAY NIGHT. A HAZARDOUS SEAS
WARNING WAS ISSUED AS CONFIDENCE IS HIGH THAT THESE VERY HIGH SEAS
WILL PERSIST INTO FRIDAY NIGHT. THE PATTERN WILL REMAIN ACTIVE WITH
THE POTENTIAL FOR HAZARDOUS SEAS TO PERSIST INTO EARLY NEXT WEEK.
BTL/FB

&&

PREV DISCUSSION... /ISSUED 305 PM PST WED DEC 9 2015/

DISCUSSION...A VERY ACTIVE WEATHER PATTERN CONTINUES FOR SOUTHERN
OREGON AND NORTHERN CALIFORNIA. A WELL-DEFINED AND OCCLUDED STORM
IS WRAPPING UP OVER THE NORTHEAST PACIFIC WATERS AND REPRESENTS
THE FIRST WEATHER-MAKER IN A SERIES THROUGH THIS FORECAST PACKAGE.
PRECIPITABLE WATER VALUES WELL OVER AN INCH ARE STREAMING AHEAD OF
THE FRONT AND WILL BRING HEAVY PRECIPITATION TO MUCH OF THE
FORECAST AREA...AND FLOODING IS A CONCERN...MAINLY URBAN AND SMALL
STREAM...AND WILDFIRE BURN SCAR-ORIENTED...VERSUS MAIN STEM RIVERS
AT THIS TIME. SNOW IMPACTS BECOME MORE PRONOUNCED AT THE TAIL END
OF THIS STORM...AND CONTINUE THROUGH NEXT WEEK AS THE AIR MASS
COOLS AND PRECIPITATION EVENTS CONTINUE TO ROLL IN. WIND IMPACTS
SHOULD BE MOST SIGNIFICANT WITH THIS FIRST SYSTEM AS A 150KT JET
TAKES AIM AT THE CWA...AND 70KT 700MB WINDS BECOME WIDESPREAD BY
EARLY THURSDAY MORNING. WE'LL PROVIDE SOME DETAIL ON EACH SPECIFIC
IMPACT.

WIND...LATEST RAP13 OUTPUT IS SUGGESTING ABOUT A 10MB PRESSURE
GRADIENT BETWEEN ACV AND OTH BY EARLY THURSDAY MORNING.
THIS...COMBINED WITH 50KT SOUTHWESTERLY WINDS AT 2000 FEET...SUGGEST
A SIGNIFICANT WIND EVENT AT THE COAST TONIGHT INTO EARLY THURSDAY
MORNING. WIND IMPACTS SHOULD BE SHORT-LIVED AT THE COAST AND WILL BE
FOCUSED MOSTLY FROM CAPE BLANCO SOUTHWARD. FURTHER INLAND...WIND
ADVISORIES HAVE BEEN ISSUED FOR THE SOUTHERN PORTIONS OF THE ROGUE
VALLEY...THE SHASTA VALLEY...AND MOST OF THE CASCADES. WINDS AREN'T
ALIGNED PERFECTLY FOR STRONG WINDS IN THE ROGUE VALLEY...BUT STILL
SHOULD MEET ADVISORY CRITERIA IN AT LEAST THE SOUTHERN PORTION...AND
WILL REMAIN GUSTY FOR MUCH OF THE DAY. EAST SIDE WINDS ARE ALREADY
BECOMING GUSTY...MUCH FASTER THAN GUIDANCE...SO HAVE ADJUSTED THE
ADVISORY AND WARNING TOWARDS AN EARLIER START TIME THIS EVENING. RAW
MODEL OUTPUT AND LOCAL MOS GUIDANCE PINPOINTS GUSTS INTO THE 60S AT
LEAST IN FAVORED LOCATIONS LIKE THE SUMMER LAKE AREA. WINDS
DIMINISH ACROSS THE AREA BY TOMORROW AFTERNOON...THOUGH WILL
REMAIN GUSTY EAST OF THE CASCADES...AND ARE NOT EXPECTED TO REACH
THE MAGNITUDE OF THIS STORM THROUGH SATURDAY AT LEAST.

PRECIPITATION THROUGH SUNDAY...A STRONG PLUME OF MOISTURE WILL
ACCOMPANY THE FRONT AS IT PUSHES ONSHORE THIS EVENING AND TONIGHT.
MODEL GUIDANCE SUGGESTS MOISTURE TRANSPORTS IN THE 99TH PERCENTILE,
WHICH IS QUITE IMPRESSIVE AS THIS IS NORMALLY ONE OF THE WETTEST
TIMES OF THE YEAR. HOWEVER, THERE HAS BEEN A SOUTHWARD SHIFT IN THE
MODEL TRANSPORT PLUMES, WHICH PLACES THE MAIN AXIS OF TRANSPORT
TONIGHT AND THURSDAY ACROSS THE NORTHERN CALIFORNIA AND FAR SOUTHERN
OREGON COASTLINES. THE END RESULT WILL BE HEAVY RAIN ALONG THE COAST
AND INTO THE  THE COASTAL RANGE SOUTH OF CAPE BLANCO, AS WELL AS
INTO THE MOUNTAINS OF WESTERN SISKIYOU COUNTY. WITH PREDOMINANT FLOW
WEST TO SOUTHWEST, THIS ALSO PRIMES THE CASCADES FOR MAXIMUM UPSLOPE
PRODUCTION. LONG STORY SHORT, WE ARE IN FOR A VERY WET TIME FOR THE
NEXT 24 TO 36 HOURS. NEARLY ALL OF THE WEST SIDE CAN EXPECT AT LEAST
AN INCH OF RAIN THROUGH THURSDAY EVENING...WITH OVER 3 INCHES OF
RAIN NEAR BROOKINGS AND UP TO 4 INCHES IN THE SOUTHERN OREGON COASTAL
RANGES AND IN WESTERN SISKIYOU COUNTY.  EAST OF THE CASCADES,
PRECIPITATION AMOUNTS WILL RANGE FROM A HALF INCH TO AN INCH, WHILE
THE CASCADES THEMSELVES COULD EASILY SEE UP TO 2 AND A HALF TO 3
INCHES OF LIQUID PRECIPITATION. ONSHORE FLOW WILL CONTINUE INTO
FRIDAY, PRODUCING WIDESPREAD SHOWERS AND UP TO AN INCH MORE RAIN
ALONG THE COAST AND IN THE MOUNTAINS BY FRIDAY NIGHT.

SNOW LEVELS WILL BE ABOVE 6000 TO 7000 FEET AS THE PRECIPITATION
FIRST ARRIVES TONIGHT, BUT THESE WILL FALL QUICKLY TO 4000 TO 4500
FEET AS THE FRONT PASSES LATE TONIGHT INTO THURSDAY MORNING. WITH
THE AMPLE MOISTURE, THIS COULD SHAPE UP TO BE THE HEAVIEST SNOWFALL
FOR OUR MOUNTAINS SO FAR THIS SEASON. ANYWHERE FROM 5 INCHES TO A
FOOT OF SNOW IS LIKELY FOR ELEVATIONS ABOVE 4000 FEET THROUGH
THURSDAY EVENING, BUT ONSHORE FLOW AND SNOW SHOWERS WILL CONTINUE
INTO FRIDAY, LIKELY PRODUCING A FEW MORE INCHES BY FRIDAY NIGHT. AS
THIS WILL IMPACT ALMOST ALL OF THE CASCADE PASSES, HAVE ISSUED A
WINTER WEATHER ADVISORY FOR SNOW, WHICH IS IN EFFECT THROUGH
THURSDAY EVENING. SEE THE WINTER WEATHER MESSAGE AT PDXWSWMFR FOR
MORE DETAILS.

ANOTHER WET SYSTEM IS EXPECTED TO ARRIVE OVER THE WEEKEND, AND IT
ALSO APPEARS TO BE A VERY WET EVENT. SNOW LEVELS WILL RISE BETWEEN
SYSTEMS, BUT WILL FALL AGAIN WITH THE NEXT ROUND OF MOISTURE. AGAIN,
SEVERAL INCHES OF RAIN ARE POSSIBLE FOR VARIOUS AREAS OF THE
FORECAST AREA, AND SNOWFALL IN THE MOUNTAINS HAS THE POTENTIAL TO BE
QUITE SIGNIFICANT. ALL TOLD, FROM TONIGHT THROUGH SUNDAY, RAINFALL
AMOUNTS ALONG THE COAST NEAR BROOKINGS AND INTO THE COASTAL RANGE
COULD RANGE FROM 10 TO 12 INCHES,WITH UP TO 7 INCHES IN THE CASCADES,
3 INCHES IN THE WEST SIDE VALLEYS, AND 2 TO 3 INCHES ON THE EAST
SIDE. WHEN THIS IS TRANSLATED TO SNOW FOR THE HIGH ELEVATIONS, THE
REAL FUN BEGINS. CURRENT PROJECTIONS BRING SNOWFALL THROUGH SUNDAY
NIGHT INTO THE 3 TO 4 FOOT RANGE IN THE CASCADES AND SISKIYOUS, WITH
UP TO 6 INCHES OF SNOW ON THE EAST SIDE. KEEP IN MIND THESE ARE 5
DAY TOTALS, AND CONFIDENCE IS ONLY MODERATE FOR THIS TIME RANGE.
GIVEN THESE VALUES AND THE EXPECTED MOISTURE, HAVE ALSO ISSUED FLOOD
WATCHES FOR THE COAST INTO THE KALMIOPSIS AND WESTERN SISKIYOU
COUNTY, AS WELL AS FOR AREA WILDFIRE BURN SCARS FOR THE PAST SEVERAL
YEARS. SUSPECT THAT URBAN AREAS, AS WELL AS MANY SMALLER STREAMS AND
RIVERS, HAVE THE POTENTIAL TO FLOOD, AND LANDSLIDES AND DEBRIS FLOWS
ARE LIKELY FOR UNSTABLE SLOPES AND THE USUAL PRONE AREAS. -BPN

OUTLOOK FOR MONDAY THROUGH WEDNESDAY...THE SUNDAY INTO MONDAY
TRANSITION LOOKS FAIRLY WELL ADVERTISED BY MODEL CONSENSUS TO BE A
TREND TOWARD COLDER TEMPERATURES AND LESSER PRECIPITATION AS THE
WEEKEND A-R EVENT PUSHES SOUTH. SNOW LEVELS LOOK TO DIP TO 1500-2000
FEET BY EARLY MONDAY AND REMAIN NEAR THAT THROUGH MID WEEK. THIS
COULD MEAN IMPACTS FOR THE LOWER WEST SIDE PASSES. UPPER HEIGHTS
BUILD BRIEFLY WITH EASTERN PACIFIC RIDGING MONDAY NIGHT THROUGH
TUESDAY AND THE BEST BEST IS FOR SHOWERS TO TAPER CONSIDERABLY IN
THIS WINDOW. BUT THE POSSIBILITY LOOKS GOOD FOR MORE SHORT WAVE
ENERGY TO RIPPLE THROUGH FROM THE NORTH BY WEDNESDAY, SO SHOWER
ACTIVITY WILL PICK BACK UP. ADDITIONAL LOWER ELEVATION SNOWS LOOK
POSSIBLE GIVEN THIS PATTERN BUT IT'S NOT REALISTIC TO HAVE
CONFIDENCE IN ANY AMOUNTS OR EXACT SNOW LEVELS A WEEK OUT. STAVISH

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WARNING UNTIL 2 PM PST THURSDAY FOR ORZ029>031.
     WINTER WEATHER ADVISORY FROM 4 AM THURSDAY TO 4 AM PST FRIDAY
     ABOVE 4500 FEET FOR FOR ORZ025-027-028.
     HIGH WIND WARNING UNTIL 5 AM PST THURSDAY FOR ORZ021-022.
     FLOOD WATCH THROUGH FRIDAY MORNING FOR ORZ021-022-024.
     HIGH SURF WARNING FROM 2 AM THURSDAY TO 2 AM PST SATURDAY FOR
     ORZ021-022.
     FLASH FLOOD WATCH THROUGH THURSDAY MORNING FOR ORZ023.
     HIGH WIND WARNING UNTIL 4 AM PST THURSDAY FOR ORZ027-028.
     WIND ADVISORY UNTIL 4 AM PST THURSDAY FOR ORZ026.

CA...HIGH WIND WARNING UNTIL 2 PM PST THURSDAY FOR CAZ083>085.
     FLASH FLOOD WATCH THROUGH THURSDAY MORNING FOR CAZ080.
     FLOOD WATCH THROUGH FRIDAY MORNING FOR CAZ080.
     HIGH WIND WARNING FROM 1 AM TO 7 AM PST THURSDAY FOR CAZ082.
     WINTER WEATHER ADVISORY FROM 4 PM THURSDAY TO 4 AM PST FRIDAY
     ABOVE 4000 FEET FOR FOR CAZ080>083.
     WIND ADVISORY UNTIL 4 AM PST THURSDAY FOR CAZ081.

PACIFIC COASTAL WATERS...
- GALE WARNING UNTIL 7 AM PST THURSDAY FOR PZZ350-356-370-376.
- HAZARDOUS SEAS WARNING UNTIL 2 AM PST SATURDAY FOR
  PZZ350-356-370.
- HAZARDOUS SEAS WARNING FROM 7 AM THURSDAY TO 2 AM PST SATURDAY
  FOR PZZ376.

BTL/NSK/FJB