Small Craft Advisory 34, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
822 PM PST THU DEC 3 2015

.UPDATE...CURRENTLY, THE COLD FRONT LIES JUST WEST OF THE WARNER
MOUNTAINS IN LAKE AND MODOC COUNTIES, AND STRONG WINDS ARE STILL
ONGOING ALONG AND TO THE EAST OF THAT AREA. ELSEWHERE, WINDS HAVE
DECREASED SIGNIFICANTLY, SO HAVE CANCELLED THE WIND ADVISORIES FOR
ALL AREAS WEST OF THE FRONT. MEANWHILE, WIDESPREAD PRECIPITATION
CONTINUES, WITH SNOW LEVELS DROPPING TO JUST BELOW 5000 FEET, AS
PER RECENT TRAVEL CAMERA IMAGES. SNOWFALL IS EXPECTED TO CONTINUE
AT A GOOD PACE IN THE MOUNTAINS OF SISKIYOU COUNTY, AND ALONG THE
CASCADES, SO WINTER HEADLINES REMAIN IN PLACE THERE.

CHANGES TONIGHT WERE MAINLY DONE TO BRING THE FORECAST IN LINE
WITH CURRENT OBSERVATIONS, WITH NO MAJOR ALTERATIONS MADE. THE
MAIN FORECAST CONCERN TONIGHT WILL BE THE UPCOMING WEEKEND STORM
SYSTEM, WHICH HAS MANY SIMILAR CHARACTERISTICS TO THE EVENT JUST
WINDING DOWN NOW.

FOR MORE INFORMATION, SEE THE PREVIOUS DISCUSSION BELOW. -BPN

&&

.AVIATION...FOR THE 04/00Z TAF CYCLE...COLD FRONT MOVED INLAND YET
SHOULD DIMINISH THROUGH THIS EVENING AS SYSTEMS PROGRESSES NORTH.
PLENTY OF MOISTURE FOR CIGS ACROSS THE ENTIRE CWA.  CONTINUED CHANCE
FOR SHOWERS THIS EVENING AS COLD AIR MASS MOVES OVER LAND.  THINKING
SOME CIGS IN THE VALLEYS COULD LOWER WITH DECREASING VISIBILITY INTO
THE OVERNIGHT HOURS.  RAIN WILL ALSO START TO TURNOVER TO SNOW AT
KINGSLEY FIELD AROUND 9 AND 10Z.  OVERALL MVFR THIS EVENING FOR THE
WEST SIDE WITH VFR CONTINUING FOR THE EAST SIDE.

-SMITH

&&

.MARINE...UPDATED 400 PM PST THURSDAY 3 DEC 2015... WINDS HAVE
DECREASED THIS EVENING AS THE COLD FRONT HAS MOVED INLAND.  WAVES ON
THE OTHER HAND STILL REMAIN HIGH AND WITHIN HAZARDOUS CONDITIONS.
LOOK FOR WAVES TO CONTINUE WITHIN SMALL CRAFT ADVISORY THROUGH
FRIDAY INTO SATURDAY.  WITH ANOTHER SYSTEM APPROACHING SATURDAY
EVENING, GALES AND STORM FORCE WINDS ARE PROBABLE FOR THE OUTER
WATERS.

-SMITH

&&

.PREV DISCUSSION... /ISSUED 408 PM PST THU DEC 3 2015/

DISCUSSION...THE COLD FRONT THAT WILL MOVE ACROSS THE REGION
TONIGHT IS BEING ACCOMPANIED BY A SURFACE LOW THAT IS MOVING TO
THE NORTHEAST FROM NEAR EUREKA AT THIS TIME. THIS LOW IS SPINNING
OFF A CLUMP OF SHOWERS THAT IS MOVING INTO EXTREME SOUTHWEST
SISKIYOU COUNTY AT THIS TIME. THE GREATEST PRECIP RATES OF THIS
STORM SHOULD BE WITH THIS BATCH OF SHOWERS INTO EARLY EVENING IN
THE MT SHASTA AREA. WINDS SHOULD ALSO DECREASE QUICKLY AFTER THIS
SURFACE LOW EXITS. A COLD AIR MASS MOVES IN THIS EVENING BEHIND
THE FRONT...AND WITH ONSHORE FLOW SHOWERS WILL CONTINUE BEHIND THE
FRONT WITH SNOW LEVELS POSSIBLY DROPPING TO I-5 PASS LEVEL BETWEEN
GRANTS PASS AND ROSEBURG AT TIMES IN HEAVIER SHOWERS THIS EVENING.
SHOWERS WILL CONTINUE OVERNIGHT INTO TOMORROW MORNING WITH ONSHORE
FLOW INCREASING AS THE LEFT EXIT REGION OF A +100KT JET NUDGES
INTO THE AREA. THERE IS A BRIEF LULL IN THE ACTION LATER FRIDAY
INTO SATURDAY AHEAD OF THE NEXT SYSTEM THAT NOW LOOKS TO BRING
PRECIP TO THE COAST SATURDAY MORNING. CURRENT MODELS HAVE WINDS AS
STRONG OR STRONGER THAN THE RECENT STORM...AND SHOULD LAST FOR A
LONGER DURATION...LASTING INTO SUNDAY MORNING. WITH THE LONGER
DURATION SOUTHERLY FLOW AHEAD OF THE FRONT SNOW LEVELS SHOULD BE A
LITTLE HIGHER THAN WITH THIS CURRENT SYSTEM. SVEN

LONG-TERM...MONDAY THROUGH THURSDAY...BROAD TROUGHING OVER THE
NORTHEAST PACIFIC OCEAN IS EXPECTED TO MAINTAIN AN ACTIVE WEATHER
PATTERN IN THE EXTENDED TIMEFRAME. THERE IS HIGH CONFIDENCE IN
MULTIPLE ATMOSPHERIC RIVER...AKA HEAVY PRECIPITATION...EVENTS DURING
THIS PERIOD.

THE EC AND GFS AGREE THAT TWO DISTINCT STORM SYSTEMS WILL AFFECT
SOUTHERN OREGON AND NORTHERN CALIFORNIA DURING THIS PERIOD. THE
FIRST WILL ARRIVE ON MONDAY WITH ABOVE NORMAL MOISTURE FOR THIS TIME
OF YEAR. SNOW LEVELS WILL BE ABOVE NORMAL FOR THIS TIME YEAR...ABOUT
7000 FEET. THIS COULD BE PROBLEMATIC IF SIGNIFICANT RAIN IMPACTS
AREAS WHERE SNOWPACK HAS GROWN IN RECENT DAYS...RESULTING IN MELTING
SNOW...RUNOFF...AND HIGHER RIVER FLOWS. THAT SAID...THE GFS MOVES
THE MOISTURE THROUGH FAIRLY QUICKLY BUT ANOTHER STORM WITH HIGH
MOISTURE TRANSPORT VALUES ARRIVES ON WEDNESDAY. SNOW LEVELS ARE
AGAIN HIGH WITH SYSTEM INITIALLY...AT 7000 FEET OR HIGHER...BUT
SHOULD FALL AS A COLD FRONT MOVES THROUGH.

GIVEN THE AMOUNT OF PRECIPITATION EXPECTED FROM MONDAY THROUGH
THURSDAY AND BEYOND...AND SNOW LEVELS EXPECTED TO BE ABOVE 7000
FEET...RIVER RISES ARE LIKELY THIS WEEK INTO THE WEEKEND.
ALSO...IT'S LIKELY THAT STRONG WINDS WILL AT LEAST ACCOMPANY ONE OR
BOTH OF THE AFOREMENTIONED STORMS NEXT WEEK.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WARNING UNTIL 10 PM PST THIS EVENING FOR ORZ030-031.
     WINTER WEATHER ADVISORY UNTIL 4 AM PST FRIDAY FOR ORZ025.
     WINTER WEATHER ADVISORY UNTIL 4 AM PST FRIDAY FOR ORZ027-028.

CA...HIGH WIND WARNING UNTIL 10 PM PST THIS EVENING FOR CAZ085.
     WINTER STORM WARNING UNTIL 4 AM PST FRIDAY FOR CAZ080>083.

PACIFIC COASTAL WATERS...STORM WATCH FROM LATE FRIDAY NIGHT THROUGH SATURDAY EVENING FOR
     PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 AM PST SATURDAY
     FOR PZZ350-356-370-376.

BPN/CZS/SBN/NSK