Weather Service Report


876 
FXUS66 KMFR 211547
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
847 AM PDT MON APR 21 2014

.SHORT TERM...A SERIES OF UPPER LEVEL TROUGHS IS EXPECTED TO MOVE
ACROSS THE REGION THIS WEEK BRINGING PRECIPITATION AND UNSETTLED
WEATHER. THIS MORNING, AN UPPER TROUGH IS LOCATED OFF THE PACNW COAST
AND A FRONT IS JUST OFFSHORE. AHEAD OF THE FRONT, SOUTHERLY
MOISTURE AND AREA OF VORTICITY WILL MOVE ACROSS THE CWA. THIS WILL
BRING SOME PRE-FRONTAL SHOWERS, MAINLY ALONG THE CASCADES AND
SISKIYOUS. THEN LATE IN THE AFTERNOON AND IN THE EVENING, EXPECT
THE FRONT TO BEGIN TO MOVE INLAND SPREADING STRATIFORM
PRECIPITATION ACROSS THE AREA THROUGH TONIGHT. 

THE FORECAST REMAINS ON TRACK WITH THE FRONTAL SYSTEM MOVING INLAND
TONIGHT. AHEAD OF THE FRONT, HAVE INCREASED THE CHANCE FOR SHOWERS
ALONG THE CASCADES AND SISKIYOUS. ALSO HAVE ADDED A WIND
ADVISORY FOR THE SUMMER LAKE AREA FOR LATE THIS AFTERNOON AND THIS
EVENING. THE NAM, RAP AND GFS MODELS SHOW A 40 TO 50 KT SOUTHWEST JET
MOVING INTO THE AREA DURING THIS PERIOD. GUIDANCE ALSO INDICATES
GUSTS NEAR 45 MPH FOR THE SUMMER LAKE AREA LATE THIS AFTERNOON
INTO THIS EVENING. EXPECT THE MAIN AREA FOR GUSTY SOUTHWEST WINDS
WILL OCCUR FROM PAISLEY NORTH ALONG HIGHWAY 31 NEAR SUMMER LAKE.
OTHER AREAS THAT WILL SEE WINDS GUSTING TO 45 MPH WILL BE OVER THE
MOUNTAINS IN LAKE COUNTY.

&&

.AVIATION...BASED ON 21/12Z TAF CYCLE...A FRONT WILL BRING SOME RAIN 
TO THE COAST LATE THIS AFTERNOON...AND PRECIPITATION WILL SPREAD 
INLAND DURING THE EVENING. EXPECT CIGS TO LOWER TO MVFR 
AT MOST WEST SIDE LOCATIONS DURING THIS TIME FRAME...AND LOWERED 
FLIGHT CONDITIONS AND PRECIPITATION SHOULD REMAIN IN PLACE THROUGH 
THE REMAINDER OF THE TAF PERIOD. EAST SIDE AND NORCAL LOCATIONS WILL 
LIKELY REMAIN VFR THROUGH MONDAY...BUT GUSTY WINDS WILL DEVELOP IN 
THE AFTERNOON. SOME AREAS OF MVFR CEILINGS AND VISIBILITIES COULD 
DEVELOP OVER THE EAST SIDE LATE TONIGHT. FREEZING LEVELS WILL DROP 
RAPIDLY BEHIND THE FRONT...REACHING DOWN TO 3000 TO 4000 FEET ABOVE 
MSL BY 12 UTC TONIGHT. -BPN


&&

.MARINE...WEST SWELLS WILL CONTINUE TO GRADUALLY SUBSIDE THROUGH 
TONIGHT AND EVENTUALLY STABILIZE AT AROUND 10 FEET ON MONDAY. 
VARIOUS SWELL TRAINS WILL MOVE THROUGH THE AREA...KEEPING SEAS AT
AROUND 10 FEET THROUGH WEDNESDAY. A WEAK FRONT WILL PASS OVER THE
WATERS TODAY...PRODUCING LIGHT NORTH WINDS (15-20 KT) BEHIND IT
INTO MONDAY EVENING. A STRONGER FRONT IS EXPECTED WEDNESDAY AND
THIS WILL BRING SOLID SMALL CRAFT ADVISORY WINDS TO ALL WATERS
WITH GALES POSSIBLE OVER THE WATERS NORTH OF CAPE BLANCO. THE
MODELS ARE STARTING TO SHOW SOME CONSISTENCY WITH THIS
SOLUTION...THUS WILL PROBABLY NEED TO HOIST A GALE WATCH OVER THE
NEXT COUPLE OF MODEL CYCLES IF THIS TREND HOLDS. THURSDAY AND
FRIDAY LOOK QUIET...BUT ANOTHER MODERATELY STRONG FRONT IS
POSSIBLE THIS WEEKEND AND PERHAPS ANOTHER EARLY NEXT WEEK.
-WRIGHT/BPN


&&

.PREV DISCUSSION... /ISSUED 353 AM PDT MON APR 21 2014/ 

DISCUSSION...THE COLD FRONT IS MOVING INTO THE COASTAL WATERS
THIS MORNING. THIS FRONT IS ON TRACK TO BRING GUSTY WINDS TO THE
HIGHER TERRAIN OF THE WEST SIDE AND VERY GUSTY WINDS IN THE
KLAMATH AND GOOSE LAKE BASINS THIS AFTERNOON AND EVENING. SO FAR
WIND SPEEDS DON'T APPEAR TO BE STRONG ENOUGH FOR A WIND ADVISORY
BUT THIS BEARS WATCHING NONETHELESS. HOWEVER WINDS ARE FORECAST TO
BE VERY STRONG AT THE UPPER HALF OF MOUNT SHASTA (50+ MPH) AND ANY
HIKERS NEED TO TAKE THIS INTO CONSIDERATION.

SHORT TERM GUIDANCE DOES NOT BRING RAIN TO INLAND VALLEYS UNTIL
LATE AFTERNOON. THIS LOOKS REASONABLE AS UPPER LEVEL STEERING FLOW
IS ALMOST PARALLEL TO THE FRONT. ALSO WITH LACK OF STRONG
SOUTHEAST WINDS..WE SHOULD SEE MINIMUM DOWNSLOPING EFFECT AND THE
ROGUE VALLEY COULD SEE RAIN ALONG THE FRONT AS IT MOVES INLAND
THIS EVENING. THE FRONT MAY ALSO HAVE A FEW WAVES DEVELOP ALONG
THE FRONT WHICH SHOULD HELP SLOW THE EASTWARD PROGRESSION. 

TONIGHT A SERIES OF STRONG WILL MOVE INLAND. THE UPPER LEVEL
TROUGH ASSOCIATED WITH THIS SYSTEM IS FAIRLY DEEP AND SHOWS A
NEGATIVELY TILTED PROFILE. THERE WILL ALSO BE A STRONG ONSHORE
FLOW WHICH WILL HELP ENHANCE PRECIPITATION ACROSS OUR FORECAST
AREA. BOTH THE GFS AND ECMWF ARE IN GOOD AGREEMENT ON RAINFALL
AMOUNTS AND TIMING. RAINFALL AMOUNTS UP TO HALF AN INCH OF RAIN IN
THE PARTS OF THE ROGUE AND UMPQUA VALLEYS ARE NOT UNREASONABLE FOR
TONIGHT TIME FRAME. PRECIPITATION IS MUCH LIGHTER EAST OF THE
CASCADES OVERNIGHT BUT THE KLAMATH BASIN IS EXPECTED TO PICK UP
TOWARD TUESDAY MORNING. SNOW LEVELS WILL REMAIN RATHER HIGH
TONIGHT AND THIS SHOULD NOT AFFECT TRAVEL ACROSS THE MAJOR PASSES.

COOLER NORTHWEST FLOW WILL BRING SNOW LEVELS DOWN ON TUESDAY.
CURRENT FORECAST CALLS FOR THE SNOW LEVELS TO LOWER TO AROUND 3500
TO 4000 FEET TUESDAY. THIS WILL DEFINITELY IMPACT TRAVELS ACROSS
THE CASCADES WITH A FEW INCHES OF SNOW POSSIBLE AND LESSER IMPACT
OVER THE SISKIYOU PASSES. WEAK SHORT WAVE RIDGING MOVES INTO THE
AREA TUESDAY AFTERNOON THROUGH TUESDAY NIGHT. PRECIPITATION CHANCE
DECREASES SOMEWHAT BUT THIS WILL BE SHORT LIVED AS A WARM FRONT
WILL BRING ANOTHER ROUND OF RAIN TO THE COAST WEDNESDAY. THIS WARM
FRONT WILL BRING VERY GUSTY WINDS TO THE COASTAL AREA WEDNESDAY
WITH RAIN SPREADING INLAND. SNOW LEVELS WILL RISE ON WEDNESDAY. THE
SECOND HALF OF THE WEEK COULD SEE SIGNIFICANT RAIN AT LEAST FOR
SOUTHWEST OREGON AND NORTHERN CALIFORNIA WITH HIGH LEVEL OF MOISTURE
TRANSPORT FROM THE PACIFIC. /FB


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...WIND ADVISORY FROM 3 PM THIS AFTERNOON TO 11 PM PDT THIS EVENING 
     FOR ORZ030-031.

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 PM PDT WEDNESDAY 
     FOR PZZ350-356-370-376. 

$$

CC





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