Hazardous Seas Warning 13, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
259 PM PDT SAT MAR 14 2015

.DISCUSSION....SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT, THE
GOOD NEWS IS THAT AFTER WAFFLING BACK AND FORTH, THE GFS, ECMWF,
NAM, AND OTHER HIGH RESOLUTION MODELS. HAVE FINALLY COME INTO A
COMMON AGREEMENT CONCERNING THE FRONTAL SYSTEM IMPACTING THE
REGION TONIGHT AND TOMORROW. THE BAD NEWS IS, THE RESULT IS A
STRONG WIND STORM, ESPECIALLY FOR THE COAST, THE EAST SIDE, AND
OVER HIGHER TERRAIN. HAVE MADE CONSIDERABLE CHANGES TO THE
FORECAST, MOSTLY IN REGARDS TO THOSE WINDS, BUT HAVE ALSO ALTERED
THE PLACEMENT AND TIMING OF PRECIPITATION.

MUCH OF THE UNCERTAINTY REGARDING THIS STORM STEMMED FROM THE
EXISTENCE AND STRENGTH OF A SURFACE LOW JUST OFFSHORE. NOW IT
APPEARS THAT THIS LOW WILL INDEED EXIST, AND IS EXPECTED TO DEEPEN
AS IT SLIDES NORTH THROUGH THE COASTAL WATERS JUST OFFSHORE OF
OREGON. THIS PATTERN IS KNOWN TO PRODUCE STRONG WINDS ALONG THE
COAST, AND WITH MODELS PRODUCING WINDS IN THE BOUNDARY LAYER AND
LOW LEVELS IN EXCESS OF 50 MPH, HAVE ISSUED A HIGH WIND WARNING
FOR THE COAST ALONG AND NORTH OF HUMBUG MOUNTAIN. MEANWHILE, ON
THE EAST SIDE AND IN NORTHERN CALIFORNIA, WINDS AT 700 MB ARE
EXPECTED TO APPROACH 60 TO 70 MPH. THIS IS A GOOD PROXY FOR WIND
GUSTS THERE, SO HAVE OPTED TO ISSUE A WIND ADVISORY FOR MUCH OF
THE AREA, WITH A HIGH WIND WARNING FOR THE USUAL PROBLEMATIC
LOCATIONS. FOR MORE INFORMATION ON THESE AREAS, PLEASE SEE THE
NON-PRECIPITATION HAZARD STATEMENT (NPWMFR).

AS FOR PRECIPITATION, THE MOISTURE FLOW INTO THE FORECAST AREA
STILL APPEARS STRONG, SUGGESTING A RATHER WELL DEFINED ATMOSPHERIC
RIVER EVENT. HOWEVER, THERE IS SOME QUESTION AS TO HOW MUCH OF
THIS MOISTURE CAN BE WRUNG OUT. AN UPPER LEVEL IMPULSE WILL HELP
PRODUCE RAIN OVER THE FORECAST AREA ALONG AND WEST OF THE CASCADES
TONIGHT. AFTER A BRIEF BREAK IN THE STEADY RAIN LATE TONIGHT, A
STRONG SHORTWAVE WILL PUSH THE FRONT INLAND LATE SUNDAY, BUT BY
THIS TIME, THE BULK OF THE MOISTURE WILL BE WELL TO THE NORTH OF
THE FORECAST AREA. DESPITE THIS, THE LATEST MODEL RUNS DO SHOW A
HEFTY SLUG OF MOISTURE PUSHING ONSHORE ALONG THE COLD FRONT SUNDAY
NIGHT. MUCH OF THIS RAIN WILL FALL OVER THE SOUTHWESTERN PORTIONS
OF THE FORECAST AREA, AS THE FRONT IS EXPECTED TO WASH OUT AS IT
MOVES FURTHER INLAND. HAVE TAKEN ALL OF THIS INTO ACCOUNT, AND
ADJUSTED PRECIPITATION CHANCES AND AMOUNTS ACCORDINGLY. ALSO IN
REGARDS TO AMOUNTS, HAVE TRENDED TOWARDS THE HIGHER RESOLUTION ARW
AND DOWNSCALE NAM, AS THERE HAS BEEN SUCCESS WITH THOSE MODELS
WITH SIMILAR SYSTEMS. RAIN WILL TAPER OFF BY MONDAY MORNING.

ANOTHER CHANGE TO THE FORECAST OCCURS IMMEDIATELY FOLLOWING THE
MAIN EVENT. THE GFS AND ECMWF HAVE RESOLVED A TROUGH SWINGING
SOUTHWEST TO NORTHEAST THROUGH THE AREA, AND ALTHOUGH THERE IS
LITTLE MOISTURE ASSOCIATED WITH IT, IT WILL PRODUCE ENOUGH
INSTABILITY TO PERHAPS BRING SOME SHOWERS, AND MAYBE EVEN A ROLL
OF THUNDER HERE OR THERE, TO MUCH OF THE FORECAST AREA.
UNCERTAINTY REMAINS HIGH, AS THIS IS THE FIRST CYCLE TO SHOW SUCH
A FEATURE, SO HAVE KEPT PRECIPITATION CHANCES AT SLIGHT TO CHANCE.
ANY SHOWERS WITHIN THE AREA SHOULD TAPER OFF TUESDAY NIGHT,
HEADING INTO THE EXTENDED PERIOD. -BPN

.LONG TERM...WEDNESDAY THROUGH SATURDAY...THE ECMWF AND GFS ARE
IN GENERAL GOOD AGREEMENT WITH A RIDGE BUILDING OVER THE PACNW
WEDNESDAY. THE 18Z GFS IS NOW COMING IN LINE WITH THE ECMWF
SOLUTION THURSDAY INTO THURSDAY NIGHT OF THE RIDGE SHIFTING TO THE
EAST AHEAD OF THE NEXT FRONT THAT SHOULD BRING PRECIPITATION INTO
THE COAST FRIDAY MORNING. SOUTH WINDS INCREASE AHEAD OF THE FRONT
BUT ARE NOT EXPECTED TO BE AS STRONG AS SUNDAY'S WINDS. FROM THERE
MODELS DIVERGE...BUT NONE ARE EXCEPTIONALLY AMPLIFIED IN EITHER
DIRECTION AND HAVE GONE WITH A ZONAL SOLUTION FOR THE REMAINDER OF
THE EXTENDED

&&

.AVIATION...FOR THE 14/18Z TAF CYCLE...AN APPROACHING FRONT WILL
BRING THICKENING AND LOWERING CLOUDS THROUGH TODAY...WITH RAIN ALONG
THE COAST AND IN THE CASCADES...SPREADING INTO WEST SIDE VALLEYS AND
TO THE EAST SIDE THIS AFTERNOON AND EVENING. PERIODS OF MVFR CIGS
ARE LIKELY ALONG THE COAST AND IN THE UMPQUA VALLEY WITH HIGHER
TERRAIN OBSCURED. CIGS/VSBYS WILL REMAIN VFR ELSEWHERE...BUT HIGHER
TERRAIN WILL BE INCREASINGLY OBSCURED. GUSTY WINDS WILL DEVELOP OVER
THE RIDGES...EAST SIDE...SHASTA VALLEY AND POSSIBLY THE ROGUE
VALLEY. -WRIGHT/SVEN

&&

.MARINE...UPDATED 1115 AM PDT SATURDAY 14 MAR 2015...SOUTH WINDS
WILL INCREASE THIS MORNING AS A COLD FRONT APPROACHES FROM THE WEST.
WINDS WILL DIMINISH A BIT THIS EVENING AND TONIGHT AS GRADIENTS
ALONG THE FRONT TEMPORARILY WEAKEN, BUT ANOTHER AREA OF LOW PRESSURE
WILL MOVE ALONG THE FRONT AND BRING INCREASED WINDS AND SEAS AGAIN
ON SUNDAY. THE LATEST MODEL GUIDANCE NOW SHOWS A SUB-1000 MB SURFACE
LOW COMING INSIDE 130W ON SUNDAY, WHICH SHOULD YIELD GALE FORCE
WINDS WITH POSSIBLE STORM FORCE WINDS OVER THE WATERS. MODELS
CONTINUE TREND TO DEEPEN THE LOW AS IT MOVES UP THE COAST SUNDAY
AFTERNOON INTO THE EVENING. THINGS WILL CALM DOWN EARLY TO MID NEXT
WEEK, BUT ANOTHER SYSTEM MAY BRING SMALL CRAFT TO GALE FORCE WINDS
AND VERY STEEP SEAS TO THE AREA LATE NEXT WEEK. -WRIGHT/SVEN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WARNING FROM 11 AM TO 11 PM PDT SUNDAY FOR
     ORZ021-022-615-618-619.
     HIGH WIND WARNING FROM 5 AM TO 11 PM PDT SUNDAY FOR
     ORZ030-031-624-625.
     WIND ADVISORY FROM 5 AM TO 11 PM PDT SUNDAY FOR ORZ029.

CA...WIND ADVISORY FROM 5 AM TO 11 PM PDT SUNDAY FOR CAZ084-085-285.
     WIND ADVISORY FROM 11 PM THIS EVENING TO 8 PM PDT SUNDAY FOR
     CAZ081-082-281-282.

PACIFIC COASTAL WATERS...GALE WATCH FROM SUNDAY AFTERNOON THROUGH SUNDAY EVENING FOR
     PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 5 PM PDT THIS AFTERNOON FOR
     PZZ350-356-370-376.
     HAZARDOUS SEAS WATCH FROM SUNDAY AFTERNOON THROUGH SUNDAY
     EVENING FOR PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 PM PDT THIS
     AFTERNOON FOR PZZ350-356-370-376.

BPN/SBN/TRW