Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 250300
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
800 PM PDT FRI OCT 24 2014

.DISCUSSION...25/00Z NAM IN.

A WARM FRONT MOVED NORTH THROUGH THE MEDFORD CWA FRIDAY AND SKIES
MOSTLY CLEARED AFTER IT PASSED THROUGH. HOWEVER...MORE CLOUDS ARE
MOVING IN AHEAD OF THE TRAILING COLD FRONT...WHICH IS POISED TO
MOVE ONSHORE SATURDAY. THE FREEZING LEVEL ROSE FROM 8600 FEET ON
THE 24/12Z KMFR SOUNDING TO 12600 FEET ON THE 25/00Z SOUNDING.

A SPLITTING LONG WAVE TROUGH REMAINS OFFSHORE AROUND 133W.
DOWNSTREAM RIDGING DEVELOPED AHEAD OF IT AND THAT IS WHAT DROVE
THE WARM FRONT NORTH.

THE SOUTHERN BRANCH OF THE TROUGH WILL MOVE ONSHORE SATURDAY
AFTERNOON AND EVENING. IT WILL PUSH A WET AND WINDY FRONT ONSHORE
SATURDAY MORNING. THIS FRONT WILL MOVE THROUGH THE MEDFORD CWA
SATURDAY AFTERNOON AND EVENING AND DEPART TO THE EAST SATURDAY NIGHT.

THE MAIN IMPACT WILL BE FROM STRONG SOUTHERLY WINDS (STRONGEST IN
THE LATE MORNING AND AFTERNOON HOURS). BUT, IT WILL ALSO PRODUCE
MODERATE TO HEAVY RAIN FOR MUCH OF THE AREA WEST OF THE CASCADES
(AND LIGHT RAIN ELSEWHERE)...ISOLATED THUNDERSTORMS (WITH THE
HIGHEST PROBABILITY NEAR THE COAST)...AND UP TO 6 INCHES OF
MOUNTAIN SNOW. THE SNOW LEVEL WILL START OFF AROUND 7000 FEET ON
SATURDAY...THEN FALL TO AROUND 5000 FEET WITH POST-FRONTAL SHOWERS
SATURDAY NIGHT.

MODERATE TO HEAVY RAIN WITH ISOLATED THUNDERSTORMS WILL REACH THE
COAST AROUND MIDNIGHT THEN SPREAD INLAND SATURDAY WITH THE HEAVIEST
PRECIPITATION OCCURRING WEST OF THE CASCADE CREST. STORM TOTAL
AMOUNTS LATE TONIGHT INTO SUNDAY MORNING ARE FORECAST TO BE UP TO
4 INCHES IN THE COASTAL RANGE OF CURRY COUNTY WITH UP TO 2 INCHES
ELSEWHERE IN CURRY...COOS...JOSEPHINE...AND WESTERN AND SOUTHERN
SISKIYOU COUNTY. UP TO AN INCH ELSEWHERE ON THE WEST SIDE AND
GENERALLY UP TO A HALF INCH ON THE EAST SIDE.

POST-FRONTAL SHOWERS WILL PERSIST INTO SUNDAY...THEN AN UPPER
LEVEL RIDGE WILL EDGE INTO THE AREA...BRINGING DRIER AND WARMER
CONDITIONS WITH WEAK OFFSHORE LOW LEVEL FLOW. MONDAY MORNING WILL
LIKELY BE FAIRLY COOL THOUGH.

MONDAY WILL BE A DRY DAY WITH THE POSSIBLE EXCEPTION OF VERY LIGHT
SHOWERS AT THE COAST NORTH OF NORTH BEND. HOWEVER...HIGH CLOUDS
WILL ALREADY BE MOVING IN AHEAD OF ANOTHER STRONG FRONT...WHICH
WILL MOVE ONSHORE LATE MONDAY NIGHT OR TUESDAY MORNING.

LONG TERM DISCUSSION FROM THE FRIDAY AFTERNOON AFD...TUESDAY
MORNING THOUGH FRIDAY. MODELS ARE IN VERY GOOD AGREEMENT STARTING
TUESDAY WITH ANOTHER WET SYSTEM IMPACTING THE AREA TUESDAY INTO
WEDNESDAY. ALTHOUGH THE JET AXIS WILL BE NORTH OF THE REGION LOW
LEVEL CONVERGENCE COMBINING WITH OROGRAPHIC LIFT WILL BRING HEAVY
PRECIPITATION TO THE WEST SIDE WITH A WETTING RAIN POSSIBLE EAST
OF THE CASCADES IN A NEAR ZONAL FLOW PATTERN.

THE UPPER LEVEL RIDGE WILL BUILD AND SHIFT EAST AS THE UPPER
LEVEL TROUGH DEEPENS OFFSHORE INTO FRIDAY MORNING WITH SHOWERS
WEAKENING OVER THE REGION THROUGH FRIDAY MORNING. FROM FRIDAY THE
ECMWF AND THE GFS VARY IN THE THE DEPTH AND LOCATION OF A CUTOFF
LOW BEYOND 130W...WITH THE ECMWF PUTTING THE LOW OFF OF THE
SOUTHERN CALIFORNIA COAST AND THE GFS LOCATING IT OFF OF THE
NORTHERN CALIFORNIA COAST. CONFIDENCE IS MUCH HIGHER ON THE
FORECAST UP TO FRIDAY...AND LOWER NEXT WEEKEND. /SVEN

&&

.AVIATION...BASED ON THE 25/00Z TAF CYCLE...WITH THE WARM FRONT
PUSHING NORTH OF THE AREA, VFR CONDITIONS PREVAIL AT MOST LOCATIONS
THIS EVENING...ASIDE FROM KRBG AND THE UMPQUA VALLEY WHICH LINGER IN
MVFR OR IFR CIGS. A COLD FRONT WILL APPROACH FROM THE WEST BEGINNING
LATER THIS EVENING INTO OVERNIGHT, AND GUSTY SOUTH TO SOUTHWEST
WINDS ARE EXPECTED TO DEVELOP IN MOST AREAS, ESPECIALLY ALONG THE
COAST AND EAST OF THE CASCADES. THE ROGUE VALLEY AND THE SHASTA
VALLEY ARE ALSO LIKELY TO SEE STRONG WINDS THROUGH MUCH OF
SATURDAY...WHILE AREAS ALONG THE COAST WILL POTENTIALLY SEE SOME
LOW LEVEL WIND SHEAR AS WINDS ABOVE THE SURFACE STRENGTHEN
CONSIDERABLY OVERNIGHT.

RAIN WILL BEGIN ALONG THE COAST AROUND 12 UTC, THEN SPREAD INLAND
THROUGH THE MORNING AND AFTERNOON. MOST AREAS WILL SEE RAIN BY THE
END OF THE TAF PERIOD. EXPECT MOSTLY VFR CONDITIONS THROUGH THE DAY,
ALTHOUGH MVFR CONDITIONS ARE LIKELY ALONG THE COAST AND WITHIN AREAS
OF HEAVIER PRECIPITATION. MOUNTAIN OBSCURATIONS WILL BECOME
WIDESPREAD AND EXTENSIVE. -BPN

&&

.MARINE...UPDATED 230 PM PDT FRI 24 OCT 2014...STRONG LOW PRESSURE
WILL MOVE THROUGH THE COASTAL WATERS OVER THE NEXT 48 HOURS.
SOUTHERLY WINDS WILL INCREASE THROUGH THIS EVENING AND TONIGHT AS
GRADIENTS TIGHTEN AHEAD OF THE LOW AND ITS ASSOCIATED COLD FRONT.
WINDS WILL REMAIN STRONG THROUGH MUCH OF SATURDAY.

THERE IS SOME QUESTION AS TO HOW STRONG WINDS WILL BECOME, AND HOW
LONG THEY WILL PERSIST. WHILE PRESSURE GRADIENT FORECASTS BETWEEN
EUREKA AND NORTH BEND WOULD SUGGEST STORM FORCE WINDS UNDER USUAL
CIRCUMSTANCES, THE FRONT WILL BE ORIENTED ROUGHLY PARALLEL TO THE
COAST, AND THIS WILL KEEP WINDS SLIGHTLY WEAKER THAN WE WOULD
TYPICALLY SEE WITH THIS STRONG OF A SYSTEM. WINDS WILL SHIFT WEST
AND BEGIN TO EASE IN THE LATE SATURDAY AFTERNOON. THIS IS SUBJECT TO
CHANGE DEPENDING ON THE TRACK OF THE LOW, BUT AT LEAST 12-18 HOURS
OF STRONG GALES TO LOW END STORM FORCE WINDS ARE NEARLY CERTAIN OVER
MUCH OF OUR WATERS. VERY STEEP AND CHAOTIC SEAS WILL ALSO ACCOMPANY
THE HIGH WINDS, COMPOSED OF MODERATE WEST SWELL AND VERY STRONG
SOUTHERLY CHOP.

CONDITIONS WILL IMPROVE SUNDAY, BUT ANOTHER FRONT MAY AFFECT THE
WATERS LATE MONDAY INTO TUESDAY. -BPN/WRIGHT

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WARNING FROM 11 PM THIS EVENING TO 11 PM PDT SATURDAY
        FOR ORZ029>031.
     HIGH WIND WARNING FROM 11 AM TO 5 PM PDT SATURDAY FOR
        ORZ021-022.
     HIGH WIND WARNING FROM 11 PM THIS EVENING TO 5 PM PDT SATURDAY
        FOR ORZ028.
     WIND ADVISORY FROM 5 AM TO 5 PM PDT SATURDAY FOR ORZ026.

CA...HIGH WIND WARNING FROM 11 PM THIS EVENING TO 5 PM PDT SATURDAY
        FOR CAZ082.
     HIGH WIND WARNING FROM 11 PM THIS EVENING TO 5 PM PDT SATURDAY
        FOR CAZ081.
     WIND ADVISORY UNTIL 11 PM PDT THIS EVENING FOR CAZ081.
     HIGH WIND WARNING FROM 11 PM THIS EVENING TO 11 PM PDT SATURDAY
        FOR CAZ083-085.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 2 AM PDT
        SATURDAY FOR PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT THIS
        EVENING FOR PZZ350-356-370-376.
     GALE WARNING FROM 2 AM TO 2 PM PDT SATURDAY FOR PZZ350-356.
     HAZARDOUS SEAS WARNING UNTIL 8 PM PDT SATURDAY FOR
        PZZ350-356-370-376.
     HIGH WIND WARNING FROM 11 AM TO 5 PM PDT SATURDAY FOR PZZ310.
     GALE WARNING UNTIL 2 PM PDT SATURDAY FOR PZZ370-376.

$$

15/15/15




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