Weather Service Report


215 
FXUS66 KMFR 291557
AFDMFR

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

.DISCUSSION...TODAY WILL FEATURE A COLD FRONT PASSAGE AND GUSTY
WINDS ACROSS MUCH OF THE FORECAST AREA. LIMITED MOISTURE WITH THE
COLD FRONT WILL MEAN GENERALLY LOW PRECIPITATION AMOUNTS AND
SPOTTY COVERAGE. HOWEVER...THUNDERSTORMS ARE POSSIBLE IN PORTIONS
OF LAKE AND MODOC COUNTIES...AND WETTING RAINS COULD ACCOMPANY ANY
STORMS THERE.

THIS IS A WINDY FRONT...WITH ALL GUIDANCE POINTING TOWARDS
NORTHWEST WIND GUSTS TO 40 MPH EAST OF THE CASCADES AND GUSTS TO
25 MPH OR MORE FOR MUCH OF THE WEST SIDE. WE HAVE ADJUSTED SOME
WINDS IN THE FORECAST UPWARDS TO ACCOUNT FOR THIS.

MODEL DATA IS POINTING TOWARDS A GENERALLY WARMER AND SUNNY
AFTERNOON TOMORROW...ESPECIALLY FOR AREAS WEST OF THE CASCADES.
PLEASE SEE THE PREVIOUS DISCUSSION BELOW FOR DETAILS ON THE
FORECAST INTO NEXT WEEK.

&&

.AVIATION...FOR THE 29/12Z TAF CYCLE...MVFR CIGS ALONG THE COAST
AND IN THE UMPQUA VALLEY WILL GRADUALLY LIFT TO VFR AROUND MID
MORNING. AREAS OF TERRAIN AND MOUNTAINS OBSCURATIONS ARE PRESENT
ALONG THE COASTAL MOUNTAINS, UMPQUA DIVIDE AND INTO THE CASCADES.
THIS AFTERNOON A COLD FRONT WILL MOVE ACROSS THE AREA AND BRING
ISOLATED TO SCATTERED SHOWERS WITH AREAS OF MVFR CIGS ALONG THE
COAST AND ISOLATED MVFR CIGS INLAND. ISOLATED THUNDERSTORMS MAY
FORM OVER EASTERN AREAS THIS AFTERNOON AND EVENING, MAINLY IN LAKE
AND MODOC COUNTIES. GUSTY NORTHWEST WINDS ARE EXPECTED THIS
AFTERNOON AND EVENING EAST OF THE CASCADES, WITH SUSTAINED
NORTHWEST WINDS COULD APPROACH 20 TO 25 KNOTS. THIS EVENING AND
TONIGHT, EXPECT AREAS OF MVFR CIGS TO DEVELOP OVER THE AREA WITH
WIDESPREAD MVFR CIGS IN THE UMPQUA VALLEY. /CC


&&

.MARINE...UPDATED 900 AM PDT FRI 29 APR 2016...A WEAK COLD
FRONT WILL MOVE ONSHORE BY THIS AFTERNOON. A THERMAL TROUGH WILL
BUILD NEAR THE COAST TONIGHT INTO SATURDAY...THEN MOVE OVER THE
COASTAL WATERS SATURDAY NIGHT. NORTH WINDS MAY REACH GALE FORCE
SATURDAY AFTERNOON AND EVENING SOUTH OF CAPE BLANCO WITH HIGH
VERY STEEP SEAS. THE THERMAL TROUGH WILL WEAKEN SUNDAY INTO MONDAY
AND WINDS AND SEAS WILL SUBSIDE AS IT DOES SO. ANOTHER COLD FRONT
WILL MOVE THROUGH THE WATERS TUESDAY INTO TUESDAY NIGHT.


&&

.PREV DISCUSSION... /ISSUED 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.

&&

.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 FROM 2 PM THIS AFTERNOON TO 5 AM PDT SUNDAY 
     FOR PZZ350-356-370-376. 

$$

NSK/DW/CC

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