Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 010416
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
916 PM PDT SAT APR 30 2016

.DISCUSSION...EVENING UPDATE. OFFSHORE FLOW WILL INTENSIFY AND
SPREAD ALL THE WAY ACROSS THE EAST SIDE BY MORNING. THIS SHOULD KEEP
THE ENTIRE REGION MOSTLY CLEAR...EVEN AT THE COAST AND MOST OF THE
COASTAL WATERS. CURRENT FORECAST LOOKS ON TRACK AND WILL NOT UPDATE
THIS EVENING. SVEN

.SHORT TERM...THIS EVENING THROUGH TUESDAY...SATELLITE IMAGERY
INDICATES MOSTLY SUNNY SKIES WEST OF THE CASCADES WITH PARTLY
CLOUDY SKIES OVER THE EAST SIDE. TODAY IS THE BEGINNING OF A
4-DAY STRETCH OF ABOVE NORMAL TEMPERATURES FOR MOST OF THE
FORECAST AREA. OFFSHORE FLOW WILL INCREASE TONIGHT AND SHOULD
RESULT IN COASTAL TEMPERATURES REACHING THE 70S AND LOW 80S SUNDAY
AFTERNOON...WITH INLAND TEMPERATURES 5 TO 15 DEGREES ABOVE NORMAL.
NORTH BEND WILL NEAR A DAILY RECORD HIGH TEMPERATURE OF 79
DEGREES ON SUNDAY...AND WE HAVE BUMPED TEMPERATURES UP SEVERAL
DEGREES HIGHER THAN MOS GUIDANCE FOR THE COAST NORTH OF CAPE
BLANCO. ESRL REFORECAST ANALOGS SUGGEST VERY WARM TEMPERATURES AT
THE COAST...AND THIS IN THE PAST HAS BEEN A GOOD INDICATOR OF
ANOMALOUSLY WARM NORTH COASTAL TEMPERATURES. A MODERATE CHETCO
EFFECT FLOW WILL BRING TEMPERATURES TO AROUND 80 DEGREES AT
BROOKINGS AS WELL SUNDAY.

SYNOPTIC DEEP FLOW SWITCHES SOUTHEASTERLY ON SUNDAY...INTRODUCING
SOME ONSHORE COMPONENT AT THE COAST AND LOWERING TEMPERATURES
SOME THERE...BUT KEEPING TEMPERATURES WELL ABOVE NORMAL INLAND AS
THE THERMAL TROUGH MOVES INLAND. SOME INSTABILITY IS EVIDENT IN
MODELS FOR MONDAY AFTERNOON EAST OF THE CASCADES BUT WITH
PRECIPITABLE WATER VALUES BELOW 0.5 INCHES AND LITTLE IN THE WAY
OF TRIGGER...HAVE KEPT THUNDERSTORMS OUT OF THE FORECAST FOR NOW.
HOWEVER...IT WILL BE WORTH KEEPING AN EYE ON SOME ENERGY MOVING UP
FROM THE SOUTHEAST TO SEE IF IT`S ENOUGH TO KICK SOMETHING OFF.

ON MONDAY FLOW TURNS MORE SOUTHERLY...USHERING IN MORE
MOISTURE...AND THIS SHOULD BE ENOUGH TO SUPPORT SOME THUNDERSTORM
ACTIVITY FOR PORTIONS OF THE WEST SIDE...CASCADES...AND EAST SIDE.
700MB FLOW IS FORECAST TO BE 10-15 KT WEST OF THE CASCADES...SO
ANY THUNDERSTORMS SHOULD PULL OFF THE TERRAIN AND AFFECT VALLEYS.

TUESDAY FEATURES A BETTER CHANCE FOR THUNDERSTORMS IN TERMS OF
MOISTURE...AND THIS IS REFLECTED AT THE MOMENT IN THUNDERSTORM
COVERAGE...WITH A SLIGHT CHANCE OF THUNDERSTORMS FROM THE ILLINOIS
VALLEY AND ROSEBURG EASTWARD TO LAKEVIEW. BUT...TOO MUCH OF A GOOD
THING CAN ACTUALLY BE AN INHIBITING FACTOR AT TIMES. AND THIS CAN
BE THE CASE WITH MOISTURE AND THUNDERSTORMS...WHERE MODELS ARE
SHOWING SOME SIGNIFICANT CLOUD COVER STREAMING INTO THE FORECAST
AREA TUESDAY...AND THIS MAY STABILIZE THINGS IN THE LOW LEVELS AND
PREVENT THUNDERSTORMS. THIS IS ANOTHER REASON TO KEEP IT A SLIGHT
CHANCE AT THE MOMENT.

.MID TERM...WEDNESDAY AND THURSDAY...MODELS ARE IN PRETTY GOOD
AGREEMENT WITH A DEEP TROUGH MOVING INTO THE CALIFORNIA WATERS.
PRETTY GOOD SOUTH FLOW AHEAD OF THIS SYSTEM WITH STRONG AND BROAD
SYNOPTIC LIFT ACCORDING TO Q-VECTORS AND QPF FIELDS. INCREASED
PROBABILITY OF PRECIPITATION FOR WEDNESDAY AND THURSDAY AS A
RESULT.

THUNDERSTORMS ARE ANOTHER TALKING POINT FOR THIS PERIOD WITH STRONG
SOUTHERLY FLOW AHEAD OF THE CLOSED LOW.  POTENTIAL INSTABILITY WILL
BE PRESENT DURING THE AFTERNOON PERIODS OF THE MID TERM, SO
THUNDERSTORMS ARE PROBABLE IF WE GET STRONG ENOUGH FORCING.

.LONG TERM...FRIDAY AND SATURDAY. FEW CHANGES WERE MADE TO DAYS 6
AND 7. SHOWER AND THUNDERSTORMS CHANCES CONTINUE AS MOISTURE AND
DYNAMICS ROTATE IN OVER OUR AREA FROM A LARGE UPPER LOW TO OUR
EAST. MODELS DIFFER ON THE PROGRESSION OF THIS LOW INLAND AND THEY
DIFFER GREATLY ON HOW MUCH PRECIPITATION WE MAY GET FROM IT. THE
12Z ECMWF IS MUCH WETTER THAN THE GFS OR CANADIAN ON BOTH DAYS,
BUT ALL SHOW SOME CHANCE FOR SHOWERS/STORMS, ESPECIALLY EAST OF
THE CASCADES. GENERALLY KEPT POPS IN THE CHANCE CATEGORY EAST OF
THE CASCADES WHERE THEY ARE CLOSER TO THE LOW AND IN THE SLIGHT
CHANCE CATEGORY ON THE WEST SIDE. -WRIGHT

&&

..AVIATION...FOR THE 01/00Z TAF CYCLE...CONDITIONS WILL REMAIN VFR
AREA-WIDE THROUGH THE TAF PERIOD. GUSTY NORTH WINDS AND SOME LOW-
LEVEL INSTABILITY MAY MAKE FOR A BUMPY APPROACH TO ALL TERMINALS
DURING THE AFTERNOON AND EVENING. -WRIGHT/BPN

&&

.MARINE...UPDATED 215 PM PDT SAT 30 APR 2016...A THERMAL
TROUGH WILL WILL CONTINUE TO PRODUCE GALES THROUGH THIS AFTERNOON
AND EVENING SOUTH OF CAPE BLANCO...WITH VERY HEAVY AND STEEP SEAS
SOUTH OF CAPE ARAGO. OBSERVATIONS AT BUOY 27 HAVE SHOWN A
SIGNIFICANT RISE IN BOTH WINDS AND SEAS, WHICH SUGGESTS THE MAIN
AXIS OF THE COASTAL JET IS CLOSER TO SHORE THAN TYPICAL. HAVE MADE
ADJUSTMENTS TO ILLUSTRATE THIS IN THE UPDATED FORECAST. THE THERMAL
TROUGH WILL WEAKEN SUNDAY INTO MONDAY AND WINDS AND SEAS WILL
GRADUALLY SUBSIDE AS IT DOES SO. A WEAK COLD FRONT WILL MOVE THROUGH
THE WATERS TUESDAY INTO TUESDAY NIGHT, WITH ONLY A BRIEF PERIOD OF
SMALL CRAFT CONDITIONS POSSIBLE WITH ITS PASSAGE. -BPN


&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT SUNDAY
     FOR PZZ356.
     GALE WARNING UNTIL 2 AM PDT SUNDAY FOR PZZ356-376.
     HAZARDOUS SEAS WARNING UNTIL 11 AM PDT SUNDAY FOR
     PZZ350-356-370-376.
     SMALL CRAFT ADVISORY UNTIL 2 AM PDT SUNDAY FOR PZZ350-370.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 2 AM TO 11 PM PDT
     SUNDAY FOR PZZ350-370.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 11 AM TO 11 PM PDT
     SUNDAY FOR PZZ376.

$$

NSK/CZS/TRW



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