Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 280355
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
855 PM PDT MON APR 27 2015

.DISCUSSION...WITH THE THERMAL TROUGH MOVING INLAND DURING THE
DAY..HIGH TEMPERATURES FOR SW OREGON WERE QUITE WARM. THE MEDFORD
AIRPORT WARMED TO 87 BUT THIS DID NOT COME CLOSE TO THE RECORD OF
95. THE THERMAL IS CROSSING THE CASCADES THIS EVENING AND IS
EXPECTED TO MOVE PAST KLAMATH FALLS SHORTLY AFTER MIDNIGHT.
ONSHORE FLOW BEHIND THE THERMAL TROUGH ALONG WITH A WEAK FRONT
TUESDAY AFTERNOON WILL LEAD TO COOLER TEMPERATURES TUESDAY AND
WEDNESDAY THAT ARE CLOSER TO SEASONAL NORMS. THE LATEST NAM12
BRING LIGHT SHOWERS TO THE COAST FROM LATE MORNING THROUGH THE
EARLY AFTERNOON...WITH SHOWERS IN THE UMPQUA BASIN AND CASCADES
MAINLY IN THE MID TO LATE AFTERNOON. THERE MAY BE SOME INSTABILITY
SHOWERS NEAR THE UMPQUA DIVIDE AND NORTHERN KLAMATH AND LAKE
COUNTIES. THE REST OF THE FORECAST AREA WILL LIKELY SEE JUST MORE
CLOUD COVER BY AFTERNOON. /FB

&&

.AVIATION...FOR THE 28/00Z TAF CYCLE. AT THE COAST...VFR WILL
PREVAIL THROUGH EARLY EVENING. AS WINDS SHIFT ONSHORE, STRATUS WITH
MVFR CIGS WILL DEVELOP WITH CIGS BECOMING IFR OVERNIGHT...WITH LIFR
CIGS POSSIBLE. EXPECT WIDESPREAD TERRAIN OBSCURATION OF THE COASTAL
RANGE. AN AREA OF LOW STRATUS CURRENTLY AROUND 10 MILES WEST OF KCEC
WILL MIGRATE NORTH AND APPROACH THE COAST ONCE THE THERMAL TROUGH
MOVES INLAND AND NORTH WINDS DECREASE...LIKELY BRINGING IFR TO LIFR
CIGS AND VIS SOUTH OF CAPE BLANCO TONIGHT.

STRATUS WILL SPREAD INTO THE UMPQUA BASIN BRINGING CIGS TO IFR
TUESDAY MORNING...WITH TERRAIN OBSCURATION OF THE COASTAL RANGE,
CASCADES, AND UMPQUA MOUNTAINS. AREAS OF FOG WITH LOCAL MVFR VIS IS
ALSO POSSIBLE. CIGS WILL LIFT AND SCATTER TO VFR IN THE UMPQUA BASIN
LATE TUESDAY MORNING...AND LIKELY DROP TO MVFR IN THE AFTERNOON AS
SHOWERS DEVELOP.

ELSEWHERE...VFR CONDITIONS WILL PREVAIL THROUGHOUT THE TAF PERIOD.
-MSC


&&

.MARINE...UPDATED 800 PM PDT MONDAY 27 APR 2015... SOUTH WINDS
WILL INCREASE AROUND MIDNIGHT AHEAD OF A WEAK COLD FRONT. THE
FRONT WILL MOVE ONSHORE TUESDAY WITH WINDS TURNING NORTHERLY BY
TUESDAY AFTERNOON. SOUTH OF GOLD BEACH NORTH WINDS COULD APPROACH
ADVISORY CRITERIA. MODERATE NORTHWESTERLY SWELL WILL MOVE INTO THE
WATERS TUESDAY AFTERNOON THROUGH WEDNESDAY MORNING. ANOTHER WEAK
FRONT WILL MOVE THROUGH THE NORTHERN WATERS WEDNESDAY. A THERMAL
TROUGH WILL BUILD NORTH ALONG THE COAST AND COULD BE STRONG ENOUGH
TO GENERATE NORTH GALES THURSDAY AND FRIDAY. /FB

&&

.PREV DISCUSSION... /ISSUED 256 PM PDT MON APR 27 2015/

DISCUSSION...27/12Z NAM/GFS IN.

A LONG WAVE RIDGE IS IN PLACE ALONG THE WEST COAST. SKIES ARE
MOSTLY CLEAR EXCEPT FOR SOME MARINE CLOUDS OVER THE COASTAL
WATERS. INLAND TEMPERATURES ARE WARMING UP NICELY. AT LOW
LEVELS...THE THERMAL TROUGH IS SWINGING INLAND OVER THE WEST SIDE
VALLEYS...AND THAT WILL MAKE TODAY THE WARMEST DAY OF THE COMING
WEEK FOR THOSE AREAS. HIGH TEMPERATURES WILL BE 10 TO 20 DEGREES
ABOVE NORMAL.

THE RIDGE WILL BREAK TO THE EAST OF THE AREA THIS EVENING. THE
THERMAL TROUGH WILL MOVE OVER THE EAST SIDE TUESDAY...AND THAT
WILL BE THE WARMEST DAY OF THE WEEK THERE WITH HIGH TEMPERATURES
BE 10 TO 20 DEGREES ABOVE NORMAL. THE EXCEPTION WILL BE NEAR THE
CASCADES WHERE IT WILL BE ABOUT AS WARM AS MONDAY...BUT STILL
10 TO 15 DEGREES ABOVE NORMAL. THIS WILL BE DUE TO INCREASING
CLOUD COVER AHEAD OF THE NEXT SYSTEM.

SPEAKING OF WHICH...A COMPLEX TWO PART SHORT WAVE EJECTED FROM
THE UPSTREAM TROUGH WILL MOVE ONSHORE TUESDAY NIGHT...FOLLOWED BY
THE WEAKENING LONG WAVE TROUGH WEDNESDAY. THE WEAKENING COLD FRONT
ASSOCIATED WITH THE SHORT WAVE WILL MOVE ONSHORE TUESDAY. IT WILL
BRING SOME LIGHT PRECIPITATION TO THE WEST SIDE AND POSSIBLY SOME
SHOWERS EAST OF THE CASCADES. THE FRONT ASSOCIATED WITH THE LONG
WAVE TROUGH WILL MOVE ONSHORE WEDNESDAY...BUT THE STORM TRACK WILL
HAVE MIGRATED TO THE NORTH BY THIS TIME AND IT WILL JUST BRUSH THE
NORTHERN PORTIONS OF THE MEDFORD CWA. LITTLE PRECIPITATION IS
EXPECTED AND WHAT DOES FALL WILL BE LIMITED TO THE NORTHERN
FRINGES OF THE MEDFORD CWA. WEDNESDAY WILL BE THE COOLEST DAY OF
THE WEEK FOR MANY INLAND LOCATIONS...BUT TEMPERATURES WILL STILL
BE AROUND 5 DEGREES ABOVE NORMAL JUST ABOUT EVERYWHERE BUT THE
UMPQUA BASIN AND THE COAST.

IN THE WAKE OF THE FRONT...OFFSHORE LOW LEVEL FLOW WILL SET UP
WEDNESDAY NIGHT WITH WEAK RIDGING ALOFT. IT WILL BE A RELATIVELY
WEAK EVENT...BUT IT WILL LAST THROUGH THURSDAY NIGHT WITH INLAND
TEMPERATURES WARMING INTO FRIDAY. THE RIDGING ALOFT WILL SETTLE
INTO NEARLY ZONAL FLOW THURSDAY INTO FRIDAY WITH A WEAK TROUGH TO
THE SOUTH.

LONG TERM...FRIDAY THROUGH MONDAY...AN UPPER TROUGH THAT ARRIVES IN
THE SHORT TERM SETTLES IN ALONG THE SOUTHERN OREGON AND NORTHERN
CALIFORNIA COAST LATE THIS WEEK AND REMAINS THERE THROUGH THE
WEEKEND INTO EARLY NEXT WEEK. WITH A SUBTROPICAL RIDGE PARKED OUT
AROUND 140W BLOCKING ANY SYSTEMS FROM THE WEST AND ZONAL FLOW TO OUR
NORTH, OUR WEATHER DURING THE LONG TERM WILL BE RATHER QUIET AND
UNCHANGING. WE WILL LIKELY SEE THE OCCASIONAL STRATUS INTRUSION ONTO
THE COAST, OTHERWISE WE EXPECT MOSTLY CLEAR SKIES AND WARMER THAN
NORMAL CONDITIONS FOR OUR AREA. I HAVEN`T GONE QUITE AS WARM AS THE
STATISTICAL GUIDANCE WOULD SUGGEST, BUT OUR FORECAST HIGHS ARE STILL
A GOOD 5-10 DEGREES ABOVE NORMAL THROUGH THE PERIOD. AS THE LANDMASS
WARMS, INSTABILITY WILL CONTINUE TO BUILD. WHILE MOST OF THE AREA
WILL REMAIN CAPPED, THERE IS AN OUTSIDE CHANCE CONVECTION COULD
BREAK THROUGH AND GIVE US A THUNDERSTORM OVER THE MOUNTAINS,
ESPECIALLY LATER IN THE PERIOD. WE WILL JUST HAVE TO KEEP AN EYE ON
THAT POTENTIAL. -WRIGHT

AVIATION...FOR THE 27/18Z TAF CYCLE. AT THE COAST AND UMPQUA
BASIN...VFR WILL PREVAIL THROUGH EARLY EVENING. AS WINDS SHIFT
ONSHORE, STRATUS WITH MVFR CIGS WILL DEVELOP AT THE COAST THIS
EVENING AND DEEPEN WITH CIGS BECOMING IFR OVERNIGHT. THIS STRATUS
WILL THEN SPREAD INTO THE UMPQUA WITH MVFR CIGS OVERNIGHT. AREAS OF
FOG WITH LOCAL MVFR VIS IS ALSO POSSIBLE. ELSEWHERE...VFR CONDITIONS
WILL PREVAIL THROUGH TUESDAY MORNING. -WRIGHT

MARINE...UPDATED 255 PM PDT MONDAY 27 APR 2015...A THERMAL
TROUGH ALONG THE COAST WILL WEAKEN AND MOVE INLAND THIS EVENING.
WINDS WILL BACK TO WESTERLY TONIGHT, AND TURN SOUTHERLY TUESDAY IN
ADVANCE OF A COLD FRONT THAT WILL MOVE THROUGH THE WATERS TUESDAY
AFTERNOON. MODERATE NORTHWESTERLY SWELL WILL MOVE INTO THE WATERS
TUESDAY AFTERNOON INTO WEDNESDAY MORNING...BRINGING SEAS TO LOW
END ADVISORY LEVEL. SEAS WILL DIMINISH WEDNESDAY AFTERNOON. WINDS
WILL TURN NORTHERLY BEHIND THE FRONT TUESDAY. PRESSURE OFFSHORE
AND ALOFT WILL BUILD, LIKELY BRINGING NORTH WINDS TO ADVISORY
LEVEL WITH POSSIBLE GALES SOUTH OF CAPE BLANCO THURSDAY AFTERNOON
AND EVENING, AND AGAIN FRIDAY AFTERNOON AND EVENING. STRONG NORTH
WINDS AND THE ASSOCIATED STEEP WIND-DRIVEN SEAS WILL LIKELY
PERSIST THROUGH THE WEEKEND. -MSC

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 5 PM TUESDAY TO 5
     AM PDT WEDNESDAY FOR PZZ350-356-370-376.

$$

FJB/TRW/FJB



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