Hazardous Seas Warning 54, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
248 PM PST FRI NOV 16 2012

.SHORT TERM...TODAY THROUGH TUESDAY. CONFIDENCE GROWS IN THE IDEA
THAT A SERIES OF STORMS WILL IMPACT THE FORECAST AREA
OVER THE WEEKEND AND THROUGH THE MIDDLE OF NEXT WEEK. THE MAIN
COMPONENTS OF THESE STORMS WILL BE VERY HAZARDOUS CONDITIONS OVER
THE COASTAL WATERS...HEAVY RAIN FOR THE COAST RANGE AND
COAST...AND STRONG WINDS THAT WILL AFFECT MOST OF THE FORECAST
AREA. SNOW LEVELS ARE EXPECTED TO GENERALLY STAY ABOVE 5000 FEET
THROUGH WEDNESDAY MORNING...SO SNOW IMPACTS WILL BE CONFINED TO THE
HIGHEST TERRAIN.

THE FIRST FRONT WILL ARRIVE AT THE COAST SATURDAY AFTERNOON.
AHEAD OF THE FRONT RADAR IS SHOWING PLENTY OF PRECIPITATION MOVING
INTO NORTHWESTERN CALIFORNIA. THIS WILL SPREAD INTO MUCH OF THE
FORECAST AREA TONIGHT. SNOW LEVELS WILL BE HIGH...BUT THE HIGHER
TERRAIN OF EASTERN SISKIYOU COUNTY ABOVE 5500 FEET COULD STILL
HAVE 5 TO 10 INCHES OF ACCUMULATING SNOW. SEE WSWMFR FOR MORE
DETAILS. SOUTH WINDS WILL ALSO BEGIN TO INCREASE SATURDAY AS SOUTH
TO NORTH PRESSURE GRADIENTS REACH THE SIGNIFICANT LEVEL OF -8MB
FROM MEDFORD TO REDDING. WIND ADVISORIES HAVE BEEN ISSUED FOR THE
EAST SIDE AND SHASTA VALLEY AT NPWMFR. 700MB SOUTHWEST WINDS
SATURDAY AFTERNOON OF 40KT SUPPORT THESE WIND ADVISORIES.

ON THE TAIL END OF THIS FRONT THERE WILL BE SOME COOLING...AND SNOW
LEVELS WILL DROP TO 4000 FEET. MOST OF THE PRECIPITATION WILL HAVE
ALREADY TAPERED OFF BUT THE CASCADES COULD SEE A QUICK SEVERAL
INCHES OF SNOW SATURDAY NIGHT.

A BREAK IN PRECIPITATION IS EXPECTED SUNDAY AFTERNOON. BY SUNDAY
NIGHT AN ATMOSPHERIC RIVER SETUP IS LIKELY...AS A FETCH OF 1IN+
PRECIPITABLE WATER VALUES IS ESTABLISHED JUST OFFSHORE. GFS-DERIVED
INTEGRATED WATER VAPOR VALUES HAVE TRENDED HIGHER OVER THE PAST
SEVERAL DAYS...AND SUGGEST A LONG-DURATION HEAVY PRECIPITATION EVENT
FROM LATE SUNDAY NIGHT THROUGH TUESDAY MORNING. ADDITIONALLY...REFORECAST
ANALOGS FROM ESRL SUGGEST THAT THE RAIN EVENT FROM MONDAY INTO
TUESDAY WILL BE IN THE 90TH PERCENTILE FOR THIS TIME OF YEAR...IN
TERMS OF 24 HOUR QPF. THE HEAVIEST RAINFALL WILL PRIMARILY IMPACT
CURRY COUNTY...WESTERN JOSEPHINE COUNTY...AND WESTERN SISKIYOU
COUNTY. AT THIS POINT THE GFS AND ECMWF DIVERGE...WITH THE GFS
SUGGESTING ANOTHER 24 HOURS OF STEADY RAINFALL AT THE COAST WHILE
THE ECMWF KICKS THE FRONT INLAND...RESULTING IN SHOWERS TUESDAY
NIGHT INTO WEDNESDAY MORNING.

DURING THE HEAVIEST PRECIPITATION...FROM MONDAY AFTERNOON INTO
WEDNESDAY MORNING...SIGNIFICANT RIVER RISES CAN BE EXPECTED...AND
SMALL STREAM AND CREEK FLOODING IS POSSIBLE. WE CONTINUE THE
HYDROLOGIC OUTLOOK AT ESFMFR...AND THIS ADDRESSES EXPECTED
HYDROLOGIC CONCERNS WITH THIS EXTENDED WET WEATHER PATTERN.

ANOTHER VERY IMPORTANT ASPECT TO THE WEATHER EARLY NEXT WEEK WILL
BE WIND. HIGH WIND WATCHES HAVE BEEN ISSUED FOR THE
COAST...MOUNTAINS...SHASTA VALLEY...AND EAST SIDE FOR SUNDAY NIGHT
INTO MONDAY NIGHT. PLEASE SEE NPWMFR FOR MORE DETAILS. 700MB FLOW
PEAKS AT A ROBUST 70KT MONDAY AFTERNOON ACROSS MUCH OF THE
FORECAST AREA. VALLEYS WILL BE WINDY AS WELL...AND WIND ADVISORIES
WILL BE CONSIDERED IN FUTURE SHIFTS.

.LONG TERM...WEDNESDAY THROUGH FRIDAY, INCLUDING THANKSGIVING DAY...WHILE THE
DETAILS ARE ANYTHING BUT PINNED DOWN, WE HAVE PRETTY HIGH CONFIDENCE
THAT UNSETTLED WEATHER WILL CONTINUE ACROSS THE AREA THROUGH THE END
OF NEXT WEEK. MODELS CONTINUE TO ADVERTISE THE LONG WAVE TROUGH
REMAINING IN THE NORTH PACIFIC WITH A BROAD WEST TO SOUTHWEST FLOW
ALOFT OVER OREGON AND NORTHERN CALIFORNIA. AN ACTIVE JET STREAM WILL
ALSO PERSIST TO THE SOUTH OF THE LONG WAVE TROUGH OVER THE PACIFIC
OCEAN. THIS WILL RESULT IN ADDITIONAL SHORTWAVES/FRONTAL SYSTEMS
MOVING ONSHORE DURING THE PERIOD CONTINUING TO BRING SUBSTANTIAL
PRECIPITATION TO COASTAL AREAS...THE UMPQUA BASIN AND INTO THE
CASCADES ALONG WITH BOUTS OF STRONG WIND. MORE RAIN ON ALREADY
SATURATED GROUND WILL CONTINUE HYDROLOGIC CONCERNS DURING THIS TIME
FRAME. FOR THOSE PLANNING TRAVEL FOR THE HOLIDAY, SNOW LEVELS ARE
EXPECTED TO BE ABOVE THE MAJOR PASSES ON WEDNESDAY, BUT MAY LOWER TO
NEAR THE PASSES THURSDAY OR FRIDAY. THERE IS LOWER CONFIDENCE HERE
AS MODELS REMAIN DIVIDED ON HOW FAR INLAND THE COLD AIR GETS WITH
ANY FRONTAL PASSAGES. HAVE SPLIT THE DIFFERENCE FOR NOW, BUT CHANGES
ARE LIKELY AS MODELS CONVERGE ON A SOLUTION. ANY BREAKS IN THIS
PATTERN APPEAR SHORT-LIVED.

&&

.AVIATION...VFR CONDITIONS WILL CONTINUE FOR MUCH OF THE FORECAST
AREA THIS AFTERNOON...WITH THE EXCEPTION OF NORTHERN CALIFORNIA
WHERE MOISTURE AND LOW CEILINGS ARE STREAMING FROM SOUTH TO NORTH.
MOUNTAIN OBSCURATION IS LIKELY IN THIS AREA THIS AFTERNOON AND
WILL SPREAD NORTHWARD INTO THE REST OF THE FORECAST AREA BY TONIGHT.
MVFR CEILINGS ARE LIKELY AT THE COAST BY THIS EVENING...AND OVER
WEST SIDE VALLEYS LATER TONIGHT. MOISTURE WILL ALSO REACH EAST
SIDE TERMINALS BY LATE TONIGHT OR EARLY SATURDAY MORNING...AND
MVFR CEILINGS ARE EXPECTED HERE AS WELL. SATURDAY WILL BECOME
WINDY AT THE COAST...OVER HIGH TERRAIN AREAS...AND EAST OF THE
CASCADES...SO EXPECT TURBULENCE TO INCREASE.

&&

.CLIMATE...THE EXPECTED HEAVY RAINFALL AT THE CURRY COUNTY COAST
EARLY NEXT WEEK WILL LIKELY BE A TOP 10 EVENT FOR NOVEMBER PER
BROOKINGS RECORDS DATING BACK TO 1912. THE CURRENT FORECAST
INDICATES THAT 4 INCHES OF RAIN IS EXPECTED FROM SUNDAY NIGHT
INTO MONDAY NIGHT...WITH POSSIBLY MORE RAIN AFTER THAT.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...WIND ADVISORY FROM 10 AM TO 10 PM PST SATURDAY FOR ORZ030-031.
     HIGH WIND WATCH FROM MONDAY MORNING THROUGH MONDAY EVENING FOR
     ORZ029>031.
     HIGH WIND WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY EVENING
     FOR ORZ021-022-024-027-028.

CA...HIGH WIND WATCH FROM MONDAY MORNING THROUGH MONDAY EVENING FOR
     CAZ085.
     HIGH WIND WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY EVENING
     FOR CAZ080>083.
     WINTER WEATHER ADVISORY UNTIL 10 PM PST SATURDAY ABOVE 5500 FEET
     FOR CAZ082-083.
     WIND ADVISORY FROM 10 AM TO 7 PM PST SATURDAY FOR CAZ081.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST SATURDAY FOR
     PZZ356-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 1 PM PST SATURDAY
     FOR PZZ356.
     GALE WATCH FROM 1 AM PST SATURDAY THROUGH SATURDAY MORNING FOR
     PZZ350.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 AM PST SATURDAY FOR
     PZZ350.
     HAZARDOUS SEAS WATCH FROM 1 AM PST SATURDAY THROUGH SATURDAY
     MORNING FOR PZZ350.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 1 AM PST SATURDAY
     FOR PZZ350-376.
     GALE WATCH FROM 10 PM PST THIS EVENING THROUGH SATURDAY MORNING
     FOR PZZ370.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 10 PM PST THIS EVENING FOR
     PZZ370.
     HAZARDOUS SEAS WATCH FROM 10 PM PST THIS EVENING THROUGH
     SATURDAY MORNING FOR PZZ370.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 PM PST THIS
     EVENING FOR PZZ370.
     HAZARDOUS SEAS WATCH FROM 1 AM PST SATURDAY THROUGH SATURDAY
     MORNING FOR PZZ376.

SK/TW