Small Craft Advisory 28, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
802 PM PST MON NOV 16 2015

.DISCUSSION...17/00Z NAM IN. 17/00Z GFS IN THROUGH 90HR.

A BROAD LONG WAVE RIDGE NOW BUILDING INTO THE AREA FROM THE
SOUTHWEST WILL CONTINUE TO DO SO INTO TUESDAY. FLOW ALOFT WILL
BECOME NORTHWESTERLY MONDAY...AND THIS PATTERN WILL PERSIST INTO
THURSDAY. SEVERAL SHORT WAVES MOVING OVER THE RIDGE WILL MOVE
ONSHORE TUESDAY AND WEDNESDAY.

THE BUILDING RIDGE IS PUSHING A WARM FRONT THROUGH THE MEDFORD CWA
AT THIS TIME. THIS IS BRINGING ANOTHER ROUND OF MOSTLY LIGHT
PRECIPITATION TO THE AREA. SNOW LEVELS WILL RISE UP TO AROUND 7000
FEET FROM THE CASCADES WEST TONIGHT. THE WARM AIR WILL TAKE A BIT
LONGER TO FILTER IN EAST OF THE CASCADES...WHERE SNOW LEVELS WILL
REMAIN NEAR THE VALLEY FLOORS TONIGHT BEFORE RISING UP TO 6000 TO
7000 FEET TUESDAY.

THE COLD AIR NEAR THE SURFACE EAST OF THE CASCADES IS THE PRIMARY
CONCERN FOR TONIGHT...AS MODEL SOUNDING INDICATE A THIN LAYER OF
SUB-FREEZING TEMPERATURES WILL PERSIST NEAR THE SURFACE. THIS
PATTERN SUPPORTS FREEZING RAIN AND/OR SLEET...DEPENDING ON THE
THICKNESS OF THE SUB-FREEZING LAYER. THE ICY CONDITIONS ARE IN THE
FORECAST...BUT THE SITUATION WILL HAVE TO BE CLOSELY MONITORED FOR
POSSIBLY HAZARDOUS CONDITIONS DEVELOPING LATER TONIGHT.

THE INCOMING SHORT WAVES WILL THEN BRING ROUNDS OF SHOWERS AND
GUSTY WINDS TO THE AREA TUESDAY AND WEDNESDAY. THE BULK OF THE
PRECIPITATION WILL FALL OVER THE COAST RANGE...CASCADES...AND
SISKIYOUS WITH LIGHT AMOUNTS OR NO MEASURABLE PRECIPITATION AT
ALL ELSEWHERE. SNOW LEVELS WILL BE QUITE HIGH BY THE TIME THE
PRECIPITATION DEVELOPS...AROUND 6500 TO 7000 FEET TUESDAY
AFTERNOON. SNOW LEVELS WILL REMAIN AROUND THAT RANGE INTO
WEDNESDAY NIGHT. THE GUSTY WINDS WILL OCCUR PRIMARILY OVER THE
RIDGES AND EAST OF THE CASCADES.

LONG TERM DISCUSSION FROM THE MONDAY AFTERNOON AFD...WEDNESDAY
NIGHT THROUGH SATURDAY NIGHT. SNOW LEVELS WILL BE HIGH DURING
THIS PERIOD...7000 FEET AND HIGHER. A LINGERING FRONTAL BOUNDARY
WILL GENERALLY REMAIN OVER THE NORTHERN SECTIONS OF THE FORECAST
AREA. THIS WILL BRING TWO MAIN ROUNDS OF PRECIPITATION TO MAINLY
AREAS ALONG AND WEST OF THE CASCADES...LEAVING SISKIYOU AND MODOC
COUNTIES IN NORTHERN CALIFORNIA...AS WELL AS AREAS EAST OF THE
CASCADES IN KLAMATH AND LAKE COUNTIES...MOSTLY DRY. THE EC IS MUCH
DRIER THAN THE GFS...KEEPING RAINFALL MAINLY IN ONLY DOUGLAS AND
COOS COUNTIES...WHEREAS THE GFS DRAGS THE FRONT FARTHER SOUTH THAN
THE EC AND BRINGS RAINFALL TO MUCH OF THE WEST SIDE BOTH THURSDAY
AND FRIDAY NIGHT.

ANOTHER SYSTEM WILL APPROACH IN THE LONG TERM, BUT CONFIDENCE IS
QUITE LOW AS THE GFS AND ECMWF DISAGREE WITH THE TIMING. THE ECMWF
IS MORE AGGRESSIVE AND BRINGS IT IN ON SUNDAY WHILE THE GFS BRINGS
IT IN ON TUESDAY. HAVE HEDGED THE BETS AND HAVE BLENDED THE TIMING
OF THE SYSTEM TO BRING CHANCE POPS WEST OF THE CASCADES ON MONDAY
WITH AVERAGE TO BELOW AVERAGE TEMPERATURES ACROSS SOUTHERN OREGON
AND NORTHERN CALIFORNIA. - NSK/SCHAAF

&&

.AVIATION...FOR THE 17/00Z TAF CYCLE...A WARM FRONT WILL
BRING WIDESPREAD MVFR CIGS, TERRAIN OBSCURATIONS AND MAINLY
LIGHT RAIN/SNOW ACROSS THE CWA TONIGHT INTO TUESDAY. LOCAL IFR
IS POSSIBLE IN SOME OF THE VALLEYS AND ALONG THE COAST. SOME LIGHT
SLEET MAY ALSO OCCUR EAST OF THE CASCADES AS WARMER AIR
ALOFT MOVES IN OVER COLDER AIR AT THE SURFACE. SPILDE

&&

.MARINE...UPDATED 400 PM PST MONDAY 16 NOV 2015...SOUTH GALES
NORTH OF CAPE BLANCO AND GUSTY SOUTH WINDS ELSEWHERE THROUGH EARLY
THIS EVENING WILL DIMINISH LATER THIS EVENING. STEEP TO VERY
STEEP HAZARDOUS SEAS WILL ALSO BE HIGHEST NORTH OF CAPE BLANCO
THROUGH THIS EVENING. AFTER WINDS DIMINISH LATER THIS EVENING...SEAS
WILL REMAIN STEEP DUE TO NORTHWEST SWELL THROUGH THE MIDDLE OF THE
WEEK. WEAKER COLD FRONTS WILL MOVE ONSHORE TUESDAY NIGHT AND THURSDAY
WITH HIGH AND STEEP SEAS AND SMALL CRAFT ADVISORY LEVEL WINDS LIKELY.
MODELS ARE SHOWING THE THURSDAY FRONT HANGING UP OVER THE AREA
FRIDAY AND THEN WASHING OUT INTO SATURDAY AS THE FLOW ALOFT SPLITS.
THIS SHOULD BRING A PERIOD OF OFFSHORE FLOW AND NORTH WINDS TO THE
WATERS LATER SATURDAY INTO SUNDAY. SPILDE

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 1 AM PST TUESDAY FOR
        PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 PM PST WEDNESDAY
        FOR PZZ356-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 1 AM TUESDAY TO 4
        PM PST WEDNESDAY FOR PZZ350-370.
     GALE WARNING UNTIL 8 PM PST THIS EVENING FOR PZZ350-370.
     HAZARDOUS SEAS WARNING UNTIL 1 AM PST TUESDAY FOR PZZ350-370.

15/15/15