Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 070008
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
407 PM PST SAT FEB 6 2016

UPDATED AVIATION DISCUSSION

.DISCUSSION...THE CLOUDS HAVE HELD ON LONGER THAN ORIGINALLY
ANTICIPATED TODAY DUE TO A STATIONARY FRONT WHICH IS DRAPED
ACROSS SOUTHERN OREGON AND A WARM FRONT OFF THE COAST. IN
ADDITION, A FEW VERY LIGHT SHOWERS ASSOCIATED WITH THIS FRONT HAVE
BEEN OBSERVED AT THE COAST AND COASTAL MOUNTAINS. ALTHOUGH THIS
FRONT IS MOVING SLOWLY, SHORT TERM MODELS ARE STILL PREDICTING A
VERY STRONG RIDGE TO DEVELOP THIS EVENING ALLOWING FOR
PRECIPITATION CHANCES TO COME TO AN END AFTER SUNSET.

THE RIDGE WILL BE THE MAIN WEATHER DRIVER FOR THE NEXT FEW DAYS.
THIS MEANS THAT FOR TONIGHT, PERIODS OF PATCHY FREEZING FOG ARE
POSSIBLE OVER THE EAST SIDE VALLEYS. FURTHERMORE, AREAS OF FOG
WILL BE POSSIBLE ACROSS THE WEST SIDE VALLEYS OVER THE NEXT SEVERAL
DAYS. AFTERNOON HIGH TEMPERATURES WILL BE HIGHLY DEPENDENT ON HOW
LONG IT TAKES FOR THE FOG TO BURN OFF EACH MORNING. ALTHOUGH MANY
PIECES OF GUIDANCE INDICATE ABOVE AVERAGE AND NEAR RECORD
TEMPERATURES ACROSS MANY PLACES WEST OF THE CASCADES, THE FOG SHOULD
LINGER LONG ENOUGH TO PREVENT THAT FROM OCCURRING. AS A RESULT, HAVE
GONE BELOW GUIDANCE.

FURTHERMORE, THE CLEAR SKIES EXPECTED EAST OF THE CASCADES WILL
ALLOW TEMPERATURES TO PLUMMET. THE COLDEST TEMPERATURES WILL
OCCUR IN THE EAST SIDE VALLEYS, PARTICULARLY TONIGHT AND TOMORROW
NIGHT. WINDIER CONDITIONS, HOWEVER, ARE EXPECTED ACROSS THE RIDGE
TOPS AND THIS WILL KEEP TEMPERATURES SLIGHTLY WARMER FOR THE
HIGHER ELEVATIONS.

STRONG UPPER LEVEL RIDGES LIKE THIS ONE, ALSO TEND TO INDICATE
THE POSSIBILITY FOR STAGNATING AIR. MIXING HEIGHTS WILL BE RATHER
LOW SINCE THE PATTERN HELPS STRENGTHEN THE LOW- LEVEL INVERSIONS,
BUT THIS SYSTEM SHOULD ALSO BRING JUST ENOUGH WIND TO PREVENT
STAGNANT CONDITIONS FROM OCCURRING. HAVE HELD OFF ON ANY AIR
STAGNATION PRODUCTS FOR NOW, BUT SMALL CHANGES IN THE FORECAST
COULD LEAD TO THE NECESSITY FOR AN ADVISORY.

THE RIDGE WILL CONTINUE TO SLOWLY DRIFT EAST NEXT WEEK...AND WEAK
SHORT WAVES EJECTING FROM THE UPSTREAM TROUGH WILL START TO MOVE
OVER THE AREA WEDNESDAY. MODELS SHOW VARIABILITY IN RUN TO RUN
SOLUTIONS AS WELL AS VARIABILITY WITH EACH OTHER REGARDING THE
EXACT TIMING AND THE STRENGTH OF THESE SHORT WAVES. TYPICALLY THE
FIRST SHORT WAVE AFTER A RIDGE HAS LITTLE EFFECT OTHER THAN
HERALDING THE END OF OFFSHORE LOW LEVEL FLOW. MORE SHORT WAVES
WILL FOLLOW, AND THEY WILL PUSH STRONGER FRONTS ONSHORE. AS A
RESULT, PRECIPITATION WILL LIKELY RETURN SOMETIME IN THE SECOND
HALF OF NEXT WEEK. THE BEST GUIDANCE FOR THE NEXT SIGNIFICANT
ROUND OF PRECIPITATION RIGHT NOW IS NEXT THURSDAY OR THURSDAY
NIGHT, BUT CONFIDENCE IS LOW. -SCHAAF

&&

.AVIATION...FOR THE 07/00Z TAF CYCLE...ONSHORE FLOW WITH A WEAK
STATIONARY BOUNDARY OVER SOUTHWEST OREGON IS BRINGING AREAS OF MVFR
AND IFR CIGS ALONG THE COAST AND INTO DOUGLAS COUNTY WITH MOUNTAIN
AND TERRAIN OBSCURATIONS FROM THE CASCADES WEST THIS EVENING.
OVERNIGHT EXPECT DRYING IN THE MID LEVELS WITH MOUNTAIN OBSCURATIONS
CLEARING. HOWEVER, VALLEY LOW CLOUDS AND FOG WILL DEVELOP AND AFFECT
AREA TERMINALS.  LATE TONIGHT AND SUNDAY MORNING BETWEEN 09-
13Z...IFR CIGS AND IFR/MVFR VISIBILITIES IN FOG ARE EXPECTED TO
DEVELOP ACROSS INLAND WEST SIDE VALLEYS. AREAS OF MVFR VISIBILITIES
AND LOCAL IFR CIGS/VISIBILITIES ARE ALSO EXPECTED TO DEVELOP IN
PATCHY FREEZING FOG FOR VALLEYS EAST OF THE CASCADES, INCLUDING AT
KLMT, LATE TONIGHT AND SUNDAY MORNING. FOG AND LOW CLOUDS ARE
EXPECTED TO GRADUALLY LIFT AND CLEAR TO VFR BETWEEN 18-20Z SUNDAY./CC


&&

.MARINE...UPDATED 200 PM PST SAT FEB 6 2016...STEEP SEAS WILL
CONTINUE INTO EARLY THIS EVENING WITH SEAS DOMINATED BY WESTERLY
SWELL...THEN SEAS ARE EXPECTED TO LOWER BELOW SMALL CRAFT ADVISORY
LEVELS TONIGHT. LIGHT SOUTHEAST WINDS ARE EXPECTED TO TONIGHT AS
HIGH PRESSURE BUILDS INTO THE AREA. WINDS ARE EXPECTED TO TURN
NORTH TO NORTHEAST SUNDAY AFTERNOON AND EVENING BUT REMAIN
LIGHT....THEN LIGHT NORTHEAST TO EAST WINDS CONTINUE ON MONDAY.
WINDS WILL SHIFT TO SOUTHERLY ON TUESDAY AS HIGH PRESSURE MOVES
INLAND. ADDITIONAL...STEEP SWELL IS EXPECTED TO ENTER THE WATERS
MONDAY AS A LONG PERIOD WEST SWELL OF AROUND 10 FEET AT 16 SECONDS
BUILDS INTO THE WATERS.

A FRONT MAY NEAR THE COASTAL WATERS ON WEDNESDAY THEN MOVE INTO THE
WATERS THURSDAY. MODELS SHOW VARIABILITY WITH THE STRENGTH AND
TIMING OF THIS FRONTAL SYSTEM THOUGH AND CONFIDENCE IS LOW ON
DETAILS FOR WAVE AND WIND FORECASTS DURING THIS PERIOD. OVERALL,
EXPECT AN INCREASE IN SEAS WEDNESDAY AND THURSDAY, WITH THE
POTENTIAL FOR SMALL CRAFT WINDS AND STEEP SEAS DURING THIS PERIOD.
ANOTHER STEEP LONG PERIOD SWELL MAY MOVE INTO THE WATERS LATE
THURSDAY AND FRIDAY. /CC

&&

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

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS
    UNTIL 5 PM PST THIS AFTERNOON FOR PZZ350-356-370-376.

$$

BMS/CC


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