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Forecast Discussion for MFR NWS Office 
000
FXUS66 KMFR 100509
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
909 PM PST TUE MAR 9 2010

.DISCUSSION...
NO UPDATE IS NECESSARY THIS EVENING AS THE FORECAST IS WELL ON TRACK.

THE STRONG COLD FRONT HAS COME ONSHORE THIS EVENING AND IS
CROSSING THE CASCADES AT THIS TIME. AS THE FRONT APPROACHED THE
COAST A FLURRY OF LIGHTNING STRIKES OCCURRED IN THE COASTAL WATERS
AS THE UPPER LEVEL COLD CORE EVIDENT ON WATER VAPOR IMAGERY DUG
SOUTHEASTWARD INTO THE BACK SIDE OF THE FRONTAL BOUNDARY. AN
UPDATE TO THE COASTAL WATERS FORECAST AND THE FORECAST ALONG THE
COAST WAS ISSUED LATE THIS AFTERNOON AS THE LIGHTNING BEGAN.

AS THE FRONT MOVED INLAND SNOW LEVELS NOSED DOWN NEAR 1500 FEET IN
THE HAYES HILL AREA ALONG HIGHWAY 199...AND ALONG HIGHWAY 96 NEAR
HAPPY CAMP...AS WELL AS ALONG INTERSTATE 5 FROM NORTH OF GRANTS
PASS TO CANYONVILLE. ALTOGETHER...REPORTS AT LOW ELEVATIONS HAVE
BEEN AN INCH OR LESS...BUT SUSPECT THAT THERE HAS BEEN MORE AND
WILL BE MORE SNOW STILL TO FALL ABOVE 2000 FEET.

SNOW LEVELS IN THE FORECAST LOOK VERY MUCH ON TRACK AND THE
CURRENT HEADLINES LOOK REASONABLE BASED ON SATELLITE...RADAR...AND
MODEL TRENDS. THE PRIMARY PRECIPITATION BAND WITH THE FRONT WILL
MOVE CONTINUE MOVING ALONG AND EAST OF THE CASCADES THIS EVENING
AND OVERNIGHT...WEAKENING AS IT DOES SO. BEHIND THE FRONT SHOWERS
WILL OCCUR OVERNIGHT...BUT WILL FOCUS ALONG THE COAST...OVER THE
HIGHER TERRAIN...AND IN AREAS FAVORED BY UPSLOPE CONDITIONS IN
NORTHWEST FLOW. SNOW LEVELS WILL LIKELY DIP TO NEAR 1500 FEET BY
MORNING. THIS MEANS THAT AREAS NORTH AND WEST OF THE BASE OF THE
SISKIYOUS WILL SEE MORE SHOWER ACTIVITY THAN AREAS OUT IN THE MAIN
VALLEY. ADDITIONALLY...EASTERN DOUGLAS COUNTY WILL LIKELY SEE
PRECIPITATION MUCH OF THE NIGHT. PRECIPITATION WILL COME TO AN END
DURING WEDNESDAY MORNING...WITH FAIR WEATHER CUMULUS LIKELY
LINGERING OVER THE HIGH TERRAIN...BUT DIMINISHING WITH
TIME...DURING WEDNESDAY AFTERNOON AND EVENING.

THE NEXT FRONT WILL FLIRT WITH THE COAST ON THURSDAY...BUT WILL
NOT MOVE INLAND UNTIL FRIDAY. THIS ONE IS WARMER ON THE FRONT
END...BUT AGAIN QUITE COLD ON THE BACK SIDE.

&&

.AVIATION...
MVFR TO VFR CONDITIONS EXIST AT MOST VALLEY LOCATIONS THIS
EVENING...EXCEPT IN THE PRIMARY FRONTAL ZONE BETWEEN MEDFORD AND
LAKEVIEW...WHERE MOSTLY IFR CONDITIONS IN RAIN AND SNOW EXIST AS
SNOW LEVELS DIP JUST BELOW 2000 FEET MSL. THE FRONT WILL CONTINUE
ACROSS AND EAST OF THE CASCADES OVERNIGHT CONTINUING IFR TO MVFR
CONDITIONS IN MOSTLY SNOW. THE WEST SIDE VALLEYS WILL BE MVFR MOST
OF THE NIGHT...WITH ISOLATED IFR IN RAIN AND SNOW SHOWERS THROUGH
EARLY WEDNESDAY MORNING. CIG VIS REDUCTIONS WILL BE MORE COMMON
AND PERSISTENT IN AREAS FAVORED BY WEST AND NW FLOW SUCH AS THE
WEST SIDE OF THE CASCADES...SPECIFICALLY TOKETEE FALLS AND
ASHLAND...AS WELL AS ALONG THE COAST. CONDITIONS WILL IMPROVE TO
VFR DURING THE LATE MORNING ALL VALLEY AREAS. MOUNTAINS ARE
OBSCURED...AND WILL GENERALLY REMAIN SO UNTIL WEDNESDAY
AFTERNOON...WHEN THEY WILL REDUCE TO PARTIAL.

&&

.PREV DISCUSSION... /ISSUED 101 PM PST TUE MAR 9 2010/

DISCUSSION...09/12Z NAM/GFS IN.

OVERALL THE MODELS ADVERTISE A SLOW PROGRESSIVE PATTERN FOR THE
NEXT WEEK WITH SIGNIFICANT BREAKS BETWEEN STORM SYSTEMS.

AN UPPER LEVEL RIDGE BROKE TO THE EAST OF THE MEDFORD CWA LAST
NIGHT AND AN INCOMING TROUGH IS PUSHING A FRONT TOWARD THE COAST.
THE MID AND HIGH LEVEL CLOUDS ASSOCIATED WITH THE FRONT ARE MOVING
ONSHORE...BUT NO PRECIPITATION YET. THAT WILL COME LATER THIS
AFTERNOON AND EVENING.

THE MAIN CONCERN WITH THIS FRONT IS UNSEASONABLY LOW SNOW
LEVELS...WHICH LOOK TO BE IN THE 1500-2000 FOOT RANGE AT THIS
TIME. GIVEN THAT THIS IS A MARITIME BASED SYSTEM...THE INCLINATION
IS TO GO WITH THE HIGH END OF THAT RANGE. MOST OF THE
PRECIPITATION ASSOCIATED WITH THIS SYSTEM WILL FALL ALONG THE
COAST AND OVER THE COAST RANGE THIS EVENING. LIGHTER PRECIPITATION
WILL DEVELOP FARTHER INLAND TONIGHT.

A WINTER STORM WARNING FOR SNOW HAS BEEN ISSUED FOR ORZ024 AND
CAZ080 ABOVE 2000 FEET FOR 6-9 INCHES OF SNOW TONIGHT AND EARLY
WEDNESDAY. WINTER WEATHER ADVISORIES ARE IN EFFECT ABOVE 2000 FEET
FOR ORZ023/025/026 AND CAZ082/083 FOR 2-5 INCHES OF SNOW TONIGHT AND
FOR ORZ027/028 FOR 5-7 INCHES OF SNOW TONIGHT. FINALLY...A WINTER
WEATHER ADVISORY IS IN EFFECT FOR CAZ081 WITH 1-2 INCHES OF SNOW
EXPECTED TONIGHT.

LARGE WESTERLY SWELL WILL BRING IN HIGH SURF THIS EVENING THROUGH
WEDNESDAY AFTERNOON.

THE TROUGH WILL MOVE EAST OF THE FORECAST AREA LATE TONIGHT AND
EARLY WEDNESDAY...THEN A BROAD LONG WAVE RIDGE WILL BUILD INTO THE
AREA WEDNESDAY AND WEDNESDAY NIGHT. POST-FRONTAL SHOWER ACTIVITY
WILL END WEDNESDAY MORNING.

THAT RIDGE WILL BREAK TO THE EAST THURSDAY MORNING. THE UPSTREAM
SYSTEM WILL BE SLOW TO COME IN SINCE IT WILL BE ORIENTED ROUGHLY
PARALLEL TO THE UPPER LEVEL SOUTHWESTERLY FLOW. SHORT WAVES
EMBEDDED IN THE FLOW WILL CAUSE WAVE DEVELOPMENT ALONG THE FRONTAL
BOUNDARY SO THE FRONT WILL OSCILLATE BACK AND FORTH OFFSHORE
THURSDAY INTO THURSDAY NIGHT. OCCASIONALLY THE FRONT WILL BE CLOSE
ENOUGH TO THE COAST FOR SOME ASSOCIATED PRECIPITATION TO DEVELOP
ONSHORE BUT IT WILL BE LIGHT AND LIMITED TO THE COAST AND COAST
RANGE.

THE MAIN FRONT WILL MOVE ONSHORE FRIDAY MORNING AND IT LOOKS LIKE
IT WILL PRODUCE SIGNIFICANT PRECIPITATION OVER MOST OF THE CWA
FRIDAY AND FRIDAY NIGHT. IT WILL ALSO BE WINDY ALONG THE COAST BUT
IT DOESN`T LOOK LIKE A HIGH WIND WARNING WILL BE NECESSARY.

THE TRAILING LONG WAVE TROUGH WILL MOVE ONSHORE FRIDAY NIGHT AND
CLEAR OUT TO THE EAST OF THE CWA EARLY SATURDAY MORNING. POST-
FRONTAL SHOWER ACTIVITY WILL END SOMETIME SATURDAY.

ANOTHER RIDGE WILL PARADE THROUGH THE AREA...BUILDING IN THROUGH
SATURDAY NIGHT. ONCE IT MOVES ONSHORE IT WILL SLOW DOWN AND BUILD
OVER THE PACIFIC NORTHWEST THROUGH SUNDAY. IT WILL FINALLY MOVE
OFF TO THE EAST MONDAY...AND BY THAT TIME THE OFFSHORE TROUGH WILL
HAVE STRENGTHENED A BIT. IT WILL PUSH A WET BUT NOT PARTICULARLY
WINDY FRONT ONSHORE TUESDAY BEFORE THE UPPER TROUGH ITSELF MOVES
ONSHORE TUESDAY AFTERNOON.

AVIATION...VFR CONDITIONS WILL PREVAIL INITIALLY...BUT PRECIPITATION
WILL BRING MVFR CIGS TO THE COAST DURING THE AFTERNOON. MVFR
CIGS/VSBYS WITH AREAS OF IFR CIGS/VSBYS IN SNOW WILL SPREAD
INLAND THIS EVENING TO THE CASCADES WITH HIGHER TERRAIN BECOMING
OBSCURED. SKIES WILL CLEAR TO VFR EVERYWHERE DURING THE DAY
WEDNESDAY.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH SURF ADVISORY UNTIL 4 PM PST WEDNESDAY FOR ORZ021-022.
     WINTER STORM WARNING UNTIL 6 AM PST WEDNESDAY ABOVE 2000 FEET
     FOR ORZ024.
     WINTER WEATHER ADVISORY UNTIL 6 AM PST WEDNESDAY ABOVE 2000 FEET
     FOR ORZ023-025-026.
     WINTER WEATHER ADVISORY UNTIL 6 AM PST WEDNESDAY FOR ORZ027-028.

CA...WINTER STORM WARNING UNTIL 6 AM PST WEDNESDAY ABOVE 2000 FEET
     FOR CAZ080.
     WINTER WEATHER ADVISORY UNTIL 6 AM PST WEDNESDAY FOR CAZ082-083.
     WINTER WEATHER ADVISORY UNTIL 6 AM PST WEDNESDAY FOR CAZ081.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 4 AM PST WEDNESDAY FOR
     PZZ350-356-370-376.
     HAZARDOUS SEAS WARNING UNTIL 10 AM PST WEDNESDAY FOR
     PZZ350-356-370-376.

$$

BTL/JRS/CC/MAW

NWS MFR Office Area Forecast Discussion