Blizzard Watch 1, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
948 AM PST FRI DEC 11 2015

.AVIATION...FOR THE 11/18Z TAF CYCLE...A CLUSTER OF MODERATE TO
HEAVY SHOWERS WILL MOVE ACROSS THE WEST SIDE THIS MORNING. THERE
HAVE BEEN A FEW LIGHTNING STRIKES IN THE CLUSTER NEAR AND JUST
INLAND FROM THE COAST, BUT INSTABILITY DECREASES INLAND, SO
THUNDERSTORMS WERE NOT INCLUDED IN THE INLAND TAFS. IN GENERAL,
WEST SIDE CONDITIONS WILL BE MVFR BUT OCCASIONAL REDUCTIONS TO
IFR CIGS AND VIS ARE POSSIBLE IN THE HEAVIEST SHOWERS. SHOWERS
WILL DIMINISH IN COVERAGE AND INTENSITY FROM WEST TO EAST LATE
THIS AFTERNOON. EAST OF THE CASCADES, RAIN/SNOW SHOWERS WILL
DEVELOP LATER THIS MORNING AS THE DISTURBANCE CROSSES THE
CASCADES. THIS WILL RESULT IN MOSTLY MVFR CONDITIONS, HOWEVER A
BRIEF PERIOD OF IFR CIGS/VIS IS CERTAINLY POSSIBLE. MOUNTAINS WILL
BE MOSTLY OBSCURED THROUGHOUT THE NEXT 24 HOURS. -WRIGHT

&&

.PREV DISCUSSION... /ISSUED 902 AM PST FRI DEC 11 2015/

DISCUSSION...THE SHORTWAVE TROUGH HAS NOW MOVED INLAND ALONG THE
COAST AND WILL CONTINUE TO MOVE EAST DURING THE DAY. THIS WILL
BRING A NET IN CREASE IN SHOWER ACTIVITY FOR THE COAST WESTSIDE
AND MOUNTAINS. SNOW LEVELS WILL REMAIN BETWEEN 3500 AND 4000 FEET,
BUT COULD LOWER FOR A BRIEF TIME IN HEAVIER SHOWERS. OVERALL THE
FORECAST TODAY THROUGH THE WEEKEND LOOKS GOOD. HOWEVER THE
CURRENT RUN OF THE NAM APPEARS TO BE AN OUTLIER AND SUGGEST THERE
COULD BE A HIGHER CONCERN FOR MODERATE TO STRONG WINDS ALONG THE
COAST SATURDAY NIGHT INTO EARLY SUNDAY MORNING WITH A LOW
DEVELOPING ALONG A FRONTAL BOUNDARY WHICH IS POSITIONED FARTHER
NORTH THEN THE GFS/EC AND GEM SOLUTIONS.

OUR MAIN FOCUS TODAY IS TO ADDRESS THE BIG STORM THIS WEEKEND. THE
MAIN IMPACT WILL BE HEAVY RAIN WITH FLOODING POSSIBLE IN THE
COQUILLE RIVER AS WELL AS SMALL STREAMS AND CREEKS AND HEAVY
MOUNTAIN SNOW. THE PREVIOUS DISCUSSION OUTLINES THESE CONCERN
WELL. SEE PREVIOUS DISCUSSION FOR DETAILS ON THIS WEEKENDS STORM.
-PETRUCELLI

MARINE...UPDATED 345 AM PST FRIDAY 11 DEC 2015....A STRONG LOW
OFF THE WASHINGTON COAST WILL BRING VERY GUSTY SOUTHWEST TO WEST
WINDS ACROSS THE WATERS TODAY INTO THIS EVENING BEFORE IT MOVES
INLAND. GALES FORCE WINDS ARE EXPECTED BEYOND 10 NM FROM SHORE,
MAINLY FROM CAPE SEBASTIAN NORTHWARD. SHOWERS AND ISOLATED
THUNDERSTORMS ARE EXPECTED TODAY AND WIND GUSTS FROM THUNDERSTORMS
MAY LOCALLY REACH GALE FORCE. SEAS HAVE LOWERED SLIGHTLY EARLY
THIS MORNING BUT ARE EXPECTED TO INCREASE AGAIN BY LATE MORNING.
SEAS WILL BE LARGE DUE TO A MIX OF 25 TO 28 FOOT WEST SWELL AND
STEEP TO VERY STEEP WIND WAVES TODAY INTO THIS EVENING...THEN SEAS
WILL GRADUALLY LOWER TO AROUND 18 FT BY SATURDAY MORNING. ANOTHER
STRONG FRONT IS EXPECTED LATE SATURDAY MORNING THROUGH EARLY
SATURDAY EVENING WITH WINDS RISING TO SOUTH GALES. THIS WILL BRING
CONTINUED VERY STEEP SEAS OF AROUND 18 FT. ADDITIONAL DISTURBANCES
WILL CONTINUE INTO EARLY NEXT WEEK WITH SEAS REMAINING STEEP TO
VERY STEEP. /CC

PREV DISCUSSION... /ISSUED 439 AM PST FRI DEC 11 2015/

DISCUSSION...UNSETTLED WEATHER WILL CONTINUE ACROSS THE AREA FOR
THE NEXT SEVERAL DAYS. LOW PRESSURE WILL MOVE ONSHORE NEAR THE
MOUTH OF THE COLUMBIA RIVER THIS MORNING. A SURFACE TROUGH
ASSOCIATED WITH THIS DISTURBANCE WILL CONTINUE TO BRING SHOWERS
ACROSS MUCH OF THE CWA THROUGH THIS EVENING. THERE CAN STILL BE
ISOLATED THUNDERSTORMS ALONG THE COAST AND JUST INLAND, WHERE SMALL
HAIL MAY ALSO OCCUR. PERIODS OF SNOW WILL OCCUR OVER THE HIGHER
TERRAIN AND WINTER WEATHER ADVISORIES (WSWMFR) HAVE BEEN ISSUED.
THESE ARE FOR ELEVATIONS ABOVE 3500 FEET IN WESTERN SISKIYOU
COUNTY...AND ALSO FOR ELEVATIONS ABOVE 4000 FEET FROM LAKE OF THE
WOODS NORTHWARD IN THE CASCADES. GUSTY WINDS ARE POSSIBLE NEAR
SUMMER LAKE THIS AFTERNOON AND EVENING, SO HAVE HOISTED A WIND
ADVISORY AT NPWMFR. THIS SYSTEM WILL MOVE QUICKLY INTO
NORTHEASTERN OREGON TONIGHT. WHILE PRECIPITATION WON'T GO AWAY
COMPLETELY, THERE WILL BE A BIT A OF BREAK.

NOT MUCH HAS CHANGED WITH RESPECT TO THE STORM EXPECTED THIS
WEEKEND. A STRONG LOW PRESSURE SYSTEM (SUB-980MB) WILL MOVE TO A
POSITION NEAR THE NORTH END OF VANCOUVER ISLAND BY SATURDAY
EVENING. THIS WILL SEND A WARM FRONT NORTHWARD ALONG THE COAST
AND INTO NORTHERN OREGON AND WASHINGTON SATURDAY FOLLOWED BY A
COLD FRONT SATURDAY NIGHT INTO SUNDAY MORNING. PRECIPITATION WILL
OVERSPREAD ALL OF THE WEST SIDE SATURDAY MORNING, THEN PUSH EAST
OF THE CASCADES IN THE AFTERNOON. MEANWHILE, SNOW LEVELS STARTING
OUT AT 3000-3500 FEET WILL SURGE TO 6000-7000 FEET BRIEFLY
SATURDAY NIGHT BEFORE PLUNGING BACK BELOW THE MAJOR PASSES AGAIN
SUNDAY MORNING. VERY HEAVY SNOW WILL ACCOMPANY THIS SYSTEM THROUGH
THE CASCADES AND THE SISKIYOU MOUNTAINS...TO THE TUNE OF 1-2 FEET
(MAYBE MORE IN SOME LOCATIONS)...WITH THE HEAVIEST AMOUNTS LIKELY
NEAR CRATER LAKE NATIONAL PARK. IT SHOULD NOTED THAT VERY STRONG
700MB WINDS (75-85KT) ARE ALSO EXPECTED TO ACCOMPANY THIS SYSTEM,
SO WINDS ARE LIKELY CAUSE BLOWING AND DRIFTING SNOW, AS WELL AS
LOCAL WHITEOUT CONDITIONS. A WINTER STORM WATCH HAS BEEN ISSUED TO
HIGHLIGHT THE THREAT FOR SATURDAY INTO SUNDAY. ANOTHER ELEMENT TO
THE STORM WILL BE HEAVY RAINFALL FOR THE LOWER ELEVATIONS. MODEL
DEPICTIONS ARE SHOWING A SOLID 2-3 INCHES OF RAIN FOR THE VALLEYS
WEST OF THE CASCADES THROUGH SUNDAY EVENING, WITH 5 TO 10 INCHES
FROM WESTERN SISKIYOU COUNTY NORTHWARD TO THE SOUTHWEST OREGON
COAST, INCLUDING THE COAST RANGES. AREAL FLOOD WATCHES HAVE BEEN
ISSUED FOR THE COAST FOR TODAY THROUGH SUNDAY AND FOR INLAND AREAS
WEST OF THE CASCADES FOR SATURDAY NIGHT THROUGH SUNDAY EVENING.
AT THE VERY LEAST, SIGNIFICANT RISES CAN BE EXPECTED ON AREA
STREAMS, CREEKS AND RIVERS WITH THE POTENTIAL FOR FLOODING.
PLEASE STAY TUNED TO THE NATIONAL WEATHER SERVICE FORECASTS FOR
UPDATES REGRADING THIS POTENTIALLY DANGEROUS STORM. THE HEAVY
PRECIPITATION EVENT WILL END SUNDAY MORNING AS THE FRONT PLOWS
INLAND. BUT, THE UPPER TROUGH WILL MOVE OVERHEAD SUNDAY AFTERNOON
AND EVENING, KEEPING POST-FRONTAL SHOWERS GOING. SNOW LEVELS WILL
LOWER FURTHER DOWN TO 1600-2000 FEET SUNDAY NIGHT INTO MONDAY
MORNING. THIS MAY RESULT IN A SMALL ACCUMULATION OF SNOW NOT TOO
FAR OFF THE VALLEY FLOOR IN THE HILLS SURROUNDING MEDFORD. SPILDE

LONG TERM...NO CHANGES (FROM THURSDAY AFTERNOON'S AFD)...MONDAY
THROUGH THURSDAY NIGHT...THE LONG TERM OPENS WITH THE DEPARTING
TROUGH OVER THE ROCKIES, WITH LARGE AMPLITUDE RIDGING OVER THE
EASTERN PACIFIC. THIS PLACES THE FORECAST AREA UNDER SWIFT
NORTHERLY FLOW, ON THE COLD SIDE OF THE BOUNDARY BETWEEN AIR
MASSES. MODELS HAVE SHOWN A POSSIBLE SHORTWAVE WITHIN THIS FLOW
MOVING SOUTH OVER OUR AREA MONDAY MORNING, WHICH WOULD LIKELY
RESULT IN SHOWER ACTIVITY THROUGH MUCH OF THE DAY. WITH SNOW
LEVELS DOWN TO ABOUT 1600 FEET, ALL BUT THE COAST AND THE WEST
SIDE VALLEY FLOORS HAVE A DECENT CHANCE OF PICKING UP SOME LIGHT
SNOW ACCUMULATIONS. EVEN THE ROGUE VALLEY NEAR MEDFORD HAS A SMALL
CHANCE, BUT CONFIDENCE IS TOO LOW TO ADD TO THE FORECAST AT THIS
TIME.

BEYOND MONDAY, MODEL FORECASTS DIVERGE, BUT SOME GENERAL TRENDS ARE
EVIDENT. THE RIDGE JUST OFFSHORE OF THE PACIFIC NORTHWEST WILL COME
UNDER  PRESSURE FROM SEVERAL WAVES EMANATING FROM A LARGE BERING
STRAIGHT TROUGH. THE ECMWF IS MORE PRONOUNCED WITH ONE SUCH FEATURE
TUESDAY, HAVING IT PASS JUST TO OUR NORTH. THIS WOULD GIVE US AN
INCREASED CHANCE FOR PRECIPITATION, BUT THE GFS IS SLOWER AND MUCH
WEAKER, KEEPING THE BULK OF THE ACTION WELL TO OUR NORTH. HAVE KEPT
A CHANCE OF SHOWER IN THE FORECAST THROUGH WEDNESDAY MORNING TO
ACCOUNT FOR THIS.

BOTH THE GFS AND ECMWF SHOVE THE BERING TROUGH TO THE SOUTHEAST
TOWARDS THE WEST COAST LATE WEDNESDAY INTO THURSDAY. THIS SYSTEM HAS
ALL THE HALLMARKS OF BEING A WET AND WINDY STORM, BUT AT THIS TIME
RANGE, THEM MODELS ARE NOT RESOLVING THE DETAILS, AND CONFIDENCE
REMAINS LOW. FOR NOW, HAVE ONLY INCREASED THE CHANCE OF
PRECIPITATION AND WINDS UNTIL CONFIDENCE INCREASES. IT DOES APPEAR
THE THE WET PATTERN WILL CONTINUE, ALTHOUGH TONED DOWN QUITE A
BIT FROM THE PREVIOUS WEEKS. -BPN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...WIND ADVISORY FROM 5 PM THIS AFTERNOON TO MIDNIGHT PST TONIGHT
     FOR ORZ030-031.
     HIGH WIND WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY MORNING
     FOR ORZ030-031.
     WINTER STORM WATCH FROM SATURDAY MORNING THROUGH SUNDAY
     AFTERNOON FOR ORZ027-028.
     FLOOD WATCH THROUGH SUNDAY EVENING FOR ORZ024.
     HIGH SURF WARNING UNTIL 2 AM PST SATURDAY FOR ORZ021-022.
     FLOOD WATCH THROUGH SATURDAY AFTERNOON FOR ORZ021-022.
     FLASH FLOOD WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY EVENING
     FOR ORZ023.
     WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING ABOVE 4000
     FEET FOR FOR ORZ027-028.
     FLOOD WATCH FROM SATURDAY EVENING THROUGH SUNDAY EVENING FOR
     ORZ026.

CA...WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING ABOVE 3500
     FEET FOR FOR CAZ080.
     FLASH FLOOD WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY EVENING
     FOR CAZ080.
     HIGH WIND WATCH FROM SATURDAY EVENING THROUGH SUNDAY MORNING FOR
     CAZ081.
     HIGH WIND WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY MORNING
     FOR CAZ085.

PACIFIC COASTAL WATERS...GALE WATCH FROM SATURDAY MORNING THROUGH
     SATURDAY EVENING FOR PZZ350-356-370-376.
     HAZARDOUS SEAS WARNING UNTIL 10 AM PST SATURDAY FOR
     PZZ350-356-370-376.
     GALE WARNING UNTIL 7 PM PST THIS EVENING FOR PZZ370-376.