Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 291122
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
422 AM PDT FRI APR 29 2016

.DISCUSSION...A WEAK TRANSITORY RIDGE WILL MOVE SOUTHEAST OUT OF
OUR AREA THIS MORNING THEN A BROAD UPPER LOW WILL MOVE INTO THE
PACIFIC NORTHWEST. FIRST AND FOREMOST...THIS SYSTEM WILL PRODUCE
GUSTY NORTHWEST WINDS THAT WILL BE STRONGEST ON THE EAST SIDE. GUSTS
TO 25 MPH ARE EXPECTED ON THE WEST SIDE BUT 40 MPH AT RIDGES AND
ON THE EAST SIDE. IT WILL ALSO BRING AN INCREASE IN MID-LEVEL
CLOUDS WITH A SLIGHT CHANCE TO CHANCE OF SHOWERS AND ALSO A SLIGHT
CHANCE OF AFTERNOON AND EARLY EVENING THUNDERSTORMS ACROSS THE FAR
EAST SIDE. THERE IS AGREEMENT ON THE TRACK AND TIMING OF AN EMBEDDED
SHORTWAVE SUCH THAT THE AREA WITH A RISK OF THUNDERSTORMS WAS
LIMITED SOUTHERN LAKE AND EASTERN MODOC COUNTIES. CLOUDS WILL
LINGER INTO EARLY SATURDAY THEN THE TROUGH WILL MOVE SOUTH THROUGH
NEVADA TO SOUTHERN CALIFORNIA ON SATURDAY AND A STRONG RIDGE WILL
BUILD OVER THE EASTERN PACIFIC INTO WESTERN CANADA. THIS WILL
PRODUCE OFFSHORE WINDS WITH DOWNSLOPE WARMING FOR BROOKINGS INTO
THE MID TO UPPER 70S ON SATURDAY AND SUNDAY. THERE WILL ALSO BE A
STRONG WARMING TREND INLAND INTO SUNDAY. A FEW CUMULUS CLOUDS ARE
LIKELY TO POP UP OVER THE HIGHER TERRAIN ON SUNDAY. THIS WILL
FORESHADOW A CHANGE IN THE PATTERN FOR NEXT WEEK.

A BROAD TROUGH OFFSHORE CENTERED OFFSHORE FROM VANCOUVER ISLAND
WILL SLOWLY SHIFT TOWARD THE COAST THROUGH TUESDAY THEN A
SHORTWAVE WILL SPLIT OFF. IT WILL MOVE SOUTHEAST TOWARD THE
SOUTHERN CALIFORNIA WATERS INTO WEDNESDAY WHILE THE MAIN LOW
MOVES INTO BRITISH COLUMBIA. THE 00Z GFS HAS CONTINUED TO TREND
TOWARD MORE COVERAGE AND SLIGHTLY HIGHER QPF WITH INSTABILITY
SHOWERS MONDAY AFTERNOON AND EVENING. I HAVE GONE WITH A MODEL
BLEND AND RAISED POPS SLIGHTLY ON MONDAY AS THE NAM...ECMWF AND
GFS EACH GENERATE PRECIPITATION. ALTHOUGH LOOKING AT THE
DETAILS...I WILL ECHO THE EARLIER SHIFT`S COMMENTS THAT THE AMOUNT
OF AVAILABLE MOISTURE AND THE STRENGTH OF A COUPLE OF EMBEDDED
SHORTWAVES IS NOT THAT IMPRESSIVE. THE PROBABILITY IS HIGHEST FOR
WESTERN SISKIYOU COUNTY INTO THE SOUTHERN OREGON SISKIYOUS AND
CASCADES.

A STRONGER SHORTWAVE AND STRONGER SOUTHERLY FLOW ALOFT WILL
ARRIVE ON TUESDAY. THIS WILL KEEP HIGH TEMPERATURES AROUND TEN
DEGREES ABOVE NORMAL AND BRING ANOTHER SLIGHT CHANCE TO CHANCE OF
MAINLY AFTERNOON AND EVENING SHOWERS AND SLIGHT CHANCE OF
THUNDERSTORMS. THE TREND WILL CONTINUE WITH THE COVERAGE OF
MAINLY AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS EXPECTED
TO INCREASE AND LIKELY REACH A PEAK ON WEDNESDAY.

DIFFLUENCE ALOFT BETWEEN THE NORTHERN AND SOUTHERN BRANCHES OF THE
LONGWAVE TROUGH WILL LIKELY DEVELOP ON THURSDAY WITH TEMPERATURES
TRENDING TOWARD NORMAL. THIS SHIFT IN THE PATTERN WILL NOT PRODUCE
MUCH CHANGE IN THE WEATHER...YET ANOTHER DAY WITH AT LEAST A
SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS.

THERE IS DECENT MODEL AGREEMENT THAT THE CLOSED LOW WILL REMAIN
OVER SOUTHERN CALIFORNIA ON FRIDAY WITH A FEW WRAP-AROUND SHOWERS
AND THUNDERSTORMS POSSIBLE...MAINLY ON THE EAST SIDE.

&&

.AVIATION...FOR THE 29/06Z TAF CYCLE...AREAS OF MVFR CIGS ALONG THE
COAST NORTH OF CAPE BLANCO WILL OVERSPREAD MOST OF THE UMPQUA VALLEY
OVERNIGHT INTO FRIDAY MORNING. TERRAIN AND MOUNTAINS WILL BE
OBSCURED BY DAY BREAK. A COLD FRONT WILL MOVE ACROSS THE AREA FRIDAY
WITH ISOLATED TO SCATTERED SHOWERS. ISOLATED THUNDERSTORMS MAY FORM
OVER THE EAST SIDE IN THE AFTERNOON. GUSTY NORTHWEST WINDS WILL ALSO
DEVELOP FRIDAY AFTERNOON, ESPECIALLY OVER THE EAST SIDE WHERE
SUSTAINED NORTHWEST WINDS COULD APPROACH 25 KNOTS. /FB

&&

.MARINE...UPDATED 307 AM PDT FRI 29 APR 2016...NORTHWEST WINDS
AND STEEP SEAS WILL EASE THIS MORNING. A COLD FRONT WILL MOVE
THROUGH THE WATERS LATE THIS MORNING WITH ANOTHER ROUND OF GUSTY
NORTH WINDS THIS AFTERNOON AND TONIGHT. OFFSHORE HIGH PRESSURE WILL
REBUILD RAPIDLY TONIGHT WITH A THERMAL TROUGH SETTING UP ALONG THE
COAST SATURDAY. THIS WILL RESULT IN THE POTENTIAL FOR GALE FORCE
WINDS AND HIGH, VERY STEEP SEAS SOUTH OF CAPE BLANCO. WINDS AND SEAS
GRADUALLY EASE SUNDAY INTO MONDAY. /CC

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...GALE WATCH FROM SATURDAY MORNING THROUGH LATE
     SATURDAY NIGHT FOR PZZ356-376.
     SMALL CRAFT ADVISORY UNTIL 5 AM PDT EARLY THIS MORNING FOR
     PZZ356-376.
     SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 5 AM PDT SUNDAY
     FOR PZZ350-356-370-376.

$$

DW/CC/BMS



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