Hazardous Seas Warning 4, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
100 PM PST WED JAN 19 2011

.DISCUSSION...19/12Z NAM/GFS IN.

THE NEXT WEEK LOOKS RELATIVELY QUIET WEATHERWISE OVER THE PACIFIC
NORTHWEST. THE ONLY INCOMING SYSTEMS WILL BE WEAK SHORT WAVES
MOVING OVER THE TOP OF A PERSISTENT OFFSHORE RIDGE.

A STRONG RIDGE IS NOW PARKED OFFSHORE BETWEEN 130W AND 140W WITH
STRONG NORTHWEST FLOW ALOFT OVER THE PACIFIC NORTHWEST. AN
EMBEDDED SHORT WAVE HAS DEPARTED EASTERN OREGON...ONLY SPOTTY
LIGHT PRECIPITATION WAS ASSOCIATED WITH IT.

THE FLOW ALOFT WILL BECOME A BIT MORE NORTHERLY AND WEAKEN AS THE
OFFSHORE RIDGE BUILDS AND DRIFTS EAST. THIS WILL SET UP OFFSHORE
LOW LEVEL FLOW TONIGHT. MOST AREAS WILL CLEAR OUT...BUT LOW CLOUDS
AND FOG WILL FORM UNDER AN INVERSION OVER THE WEST SIDE VALLEYS.
THESE MAY BE SLOW TO CLEAR THURSDAY. IT WILL GET COLD ALONG THE
NORTH COAST...SO WILL ISSUE A FROST ADVISORY FOR ORZ021 FOR
TONIGHT.

THE RIDGE WILL WEAKEN THURSDAY INTO FRIDAY...THEN A SHORT WAVE
WILL FLATTEN IT OUT FRIDAY AND MOVE ONSHORE FRIDAY AFTERNOON AND
EVENING. THIS WILL BRING THE NEXT CHANCE OF PRECIPITATION TO THE
AREA FRIDAY INTO FRIDAY NIGHT...BUT THE AMOUNTS WILL BE LIGHT.

THE RIDGE WILL REBUILD SATURDAY. IT WILL BE WEAKER BUT ALSO A BIT
CLOSER TO THE COAST. THIS WILL GIVE THE OVERRIDING SHORT WAVES
MORE OF AN INLAND TRAJECTORY...THE "INSIDE SLIDERS"...WHICH ARE
USUALLY DRY OR NEARLY DRY SYSTEMS. ONE SUCH WAVE WILL MOVE THROUGH
OREGON SATURDAY NIGHT AND A WEAKER ONES WILL FOLLOW.  EXPECT
ANOTHER OFFSHORE FLOW EVENT SATURDAY NIGHT AND THE VALLEY
INVERSION WILL SET UP OVER THE WEST SIDE VALLEYS AGAIN FOR ANOTHER
LOW CLOUDS/FOG EPISODE. THERE ARE SOME DIFFERENCES BETWEEN THE
19/12Z GFS AND THE 19/12Z ECMWF EARLY NEXT WEEK...THE ECMWF
BRINGS IN A STRONGER SHORT WAVE THAN THE GFS NEXT MONDAY NIGHT.
THE GFS SCENARIO IS DRY WHILE THE ECMWF BRINGS IN SOME LIGHT
PRECIPITATION. OTHER THAN THAT...BOTH MODELS ARE DRY SATURDAY
THROUGH NEXT WEDNESDAY. AIR STAGNATION WILL BECOME AN ISSUE AGAIN
FOR THE WEST SIDE VALLEYS NEXT WEEK...ESPECIALLY IF THE GFS
SCENARIO VERIFIES.

&&

.AVIATION...VFR CONDITIONS WILL PREVAIL THROUGH THURSDAY...EXCEPT
FOR AREAS OF MVFR TO IFR CIGS/VSBYS OVER THE WEST SIDE VALLEYS
WHICH WILL BURN OFF TO MVFR CIGS TO VFR WITH LOCAL HIGHER TERRAIN
OBSCURATIONS BY LATE THURSDAY MORNING.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS FROM 3 PM
        THIS AFTERNOON TO 10 PM PST THIS EVENING FOR PZZ356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 AM PST THURSDAY
        FOR PZZ356-370.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 10 PM PST THIS EVENING FOR
        PZZ370.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 10 PM PST THURSDAY FOR
        PZZ376.
     HAZARDOUS SEAS WARNING FROM 4 PM THIS AFTERNOON TO 4 AM PST
        THURSDAY FOR PZZ376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 PM PST THIS
        AFTERNOON FOR PZZ376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 PM PST THIS
        EVENING FOR PZZ350.

15/05/16