Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 100158
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
600 PM PST TUE FEB 9 2016

AVIATION AND MARINE UPDATED

.DISCUSSION...THE LATEST VISIBLE IMAGE SHOWS HIGH CLOUDS MOVING IN
FROM THE SOUTHWEST AND ARE THICKER IN THE SOUTHWEST PART OF THE
FORECAST AREA. HIGH AND SOME MID LEVEL CLOUDS WILL REMAIN TONIGHT,
BUT PROBABLY NOT ENOUGH TO KEEP LOW CLOUDS AND PATCHY FOG FROM
FORMING IN THE SAME AREAS AS THE PAST FEW NIGHTS.

THE UPPER RIDGE WILL GRADUALLY WEAKEN WITH THE RIDGE AXIS SHIFTING
EAST OVER THE NEXT FEW DAYS. THIS WILL OPEN UP THE DOOR FOR MORE
CLOUDS TO MOVE INTO THE AREA. ALSO A COUPLE OF WEAK FRONTS WILL MOVE
INTO THE AREA. THE FIRST FRONT IS EXPECTED TO ARRIVE WEDNESDAY
MORNING. I SUSPECT THE THE MODELS, IN PARTICULAR THE NAM ARE TOO
BULLISH WITH THE QPF FIELDS ALONG THE COAST AND MAY ONLY BE THE
SACRIFICIAL LAMB. TYPICALLY WHEN FRONTS LIKE THIS RUN INTO A RIDGE
(ESPECIALLY ONE THAT IS RATHER STRONG FOR THIS TIME OF THE YEAR)
THEY TEND TO WEAKEN AND DISSIPATE, HENCE THE REASONING FOR KEEPING
POPS BELOW GUIDANCE. HOWEVER, THE OMEGA FIELDS ARE HIGHER AT THE
COAST EARLY WEDNESDAY MORNING WHICH WOULD BE AN ARGUMENT FOR HIGHER
POPS. IT WILL BE INTERESTING WHAT THE HRRR SHOWS LATER THIS EVENING
AND TONIGHT (CURRENT RUN ONLY GOES OUT TO 3AM PST). THE EVENING AND
NIGHT SHIFT MAY NEED TO REEVALUATE THIS AND INCREASE POPS ALONG THE
COAST FOR WEDNESDAY MORNING IF THERE`S STRONGER EVIDENCE TO SUPPORT
IT.

SHOWERS (IF WE GET ANY) ON WEDNESDAY MORNING SHOULD BE CONFINED TO
THE COAST. THE REST OF THE AREA WILL BE DRY WITH MORE CLOUD COVER
AND COOLER TEMPERATURES, BUT STILL ABOVE NORMAL FOR THIS TIME OF THE
YEAR. THE PATTERN DOES NOT CHANGE MUCH ON THURSDAY. HOWEVER A WARM
FRONT WILL LIFT NORTH JUST OFF THE OREGON COAST. THE MODELS KEEP
MOST OF THE PRECIP OFFSHORE IN THE MORNING, THEN SHOWS SOME INLAND
DURING THE AFTERNOON. SUSPECT THIS ALSO MAY BE OVERDONE. INSTABILITY
IS MARGINAL AT BEST AND THE TRIGGER IS WEAK OR NON- EXISTENT.
THEREFORE, CONFIDENCE IS LOW THAT WE`LL GET ANYTHING. SO WE`LL
KEEP THINGS DRY FOR NOW BUT AS PREVIOUSLY MENTIONED, LATER SHIFTS
WILL WANT TO REEVALUATE.

THE RIDGE SHIFTS EAST AND WEAKENS FRIDAY AS THE UPPER TROUGH PUSHES
EAST INTO THE AREA BRINGING THE BEST CHANCE FOR MEASURABLE RAIN.
SNOW LEVELS WILL LOWER ON FRIDAY, BUT WILL REMAIN ABOVE ALL THE
PASSES. -PETRUCELLI

.LONG TERM (SATURDAY THROUGH TUESDAY)...A MORE WESTERLY JETSTREAM
WILL BRING A WARM FRONT INLAND ON SATURDAY. SNOW LEVELS ON SATURDAY
WILL RANGE FROM AROUND 5500 FEET IN OREGON AND UP TO 7000 FEET IN
THE MOUNT SHASTA AREA. BOTH THE GFS AND THE ECMWS ARE IN A FAIRLY
GOOD AGREEMENT SO CONFIDENCE IS HIGH ON OUR FORECAST AREA SEEING
MEASURABLE PRECIPITATION.

BY MONDAY HOWEVER BOTH MODELS STRENGTHENS THE RIDGE OVER THE WEST
COAST IN RESPONSE TO AN UPSTREAM TROUGH IN THE GULF OF ALASKA
ALTHOUGH THE RIDGE ON ECMWF IS NOT AS STRONG AND ALLOWS SOME
OVERRUNNING. AS A RESULT WE ARE KEEPING MONDAY DRY BUT RE-INTRODUCE
CHANCE POPS FOR COOS AND DOUGLAS COUNTIES ON TUESDAY. BOTH MODELS
INDICATE WE MAY SHIFT BACK TO A WET PATTER AROUND THE MIDDLE OF NEXT
WEEK. /FB

&&

.AVIATION...FOR THE 10/00Z TAF CYCLE...EXPECT LIFR CIGS IN THE
UMPQUA BASIN LATE TONIGHT GIVEN THE MOIST BOUNDARY LAYER.
ALONG THE COAST...VFR CONDITIONS EXPECTED UNTIL A WEAKENING FRONT
BRINGS MVFR CIGS LATE WEDNESDAY MORNING. ELSEWHERE...VFR EXPECTED
FOR THE ENTIRE TAF PERIOD. -MSC

&&

.MARINE...UPDATED 300 PM PST TUE FEB 9 2016....SYNOPSIS FOR THE
SOUTHERN OREGON COASTAL WATERS... SOUTH WINDS WILL VEER TO SOUTHWEST
THROUGH TONIGHT AS A WEAKENING FRONT APPROACHES. THIS FRONT WILL
MOVE IN VERY EARLY WEDNESDAY MORNING...BRINGING A CHANCE FOR
LIGHTRAIN IN THE OUTER WATERS. ANOTHER WEAK WARM FRONT WILL COME IN
FROM THE SOUTH INTO THE MARINE WATERS LATE WEDNESDAY NIGHT. THERE
WILL BE A BRIEF PERIOD OF ADVISORY LEVEL CONDITIONS AHEAD OF THE
FRONT WEDNESDAY AFTERNOON IN THE NORTHERN OUTER WATERS.

A STRONG LOW PRESSURE SYSTEM IN THE BERING SEA WILL STEER A SERIES
OF FRONTS INTO THE COASTAL WATERS THURSDAY THROUGH SATURDAY. THE
NEXT CHANCE FOR ADVISORY LEVEL...OR HIGHER... CONDITIONS AFTER
WEDENESDAY WILL BE THURSDAY AFTERNOON...WITH MULTIPLE MODERATE SWELL
TRAINS COMBINING WITH MODERATE WIND WAVES. WEST SWELL WILL BUILD TO
AROUND 14 FEET AT 17 SECONDS FRIDAY MORNING. -MSC

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS FROM 10 AM TO 4 PM PST WEDNESDAY
     FOR PZZ370.

$$


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