Weather Service Report


408 
FXUS66 KMFR 070900
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
100 AM PST SUN FEB 7 2016

.DISCUSSION...07/00Z NAM/GFS IN.

THE NORTHERN HEMISPHERIC PATTERN CONTINUES TO SHOW A NEAR
TEXTBOOK 5 WAVE PATTERN AROUND THE GLOBE WITH MODERATE AMPLITUDES.
THIS PATTERN WILL CONTINUE BUT LONGITUDINAL FLOW WILL
INCREASE...CREATING A MORE BLOCKY PATTERN AROUND THE GLOBE.
THE PATTERN WILL REMAIN PROGRESSIVE...BUT WILL SLOW DOWN OVER THE
NEXT SEVERAL DAYS AS A STRONG RIDGE BUILDS OVER THE EASTERN
PACIFIC AND WESTERN NORTH AMERICA.

THE RIDGE WILL MOVE VERY SLOWLY EAST...AMPLIFYING THROUGH MONDAY.
BUT THAT TIME IT WILL BE DIRECTLY OVER THE MEDFORD CWA. DRY
CONDITIONS AND LOW LEVEL OFFSHORE FLOW WILL PERSIST INTO TUESDAY
AND TEMPERATURES WILL WARM TO ABOVE SEASONAL VALUES...ESPECIALLY
ALONG THE SOUTH COAST AND OVER THE RIDGES. MOSTLY CLEAR SKIES WILL
PREVAIL OVER MOST OF THE AREA. THE EXCEPTION WILL BE THE WEST SIDE
VALLEYS...WHERE WARM AIR ALOFT WILL STRENGTHEN INVERSIONS...WHICH
WILL TEND TO KEEP CLOUD COVER AND COOLER AIR TRAPPED OVER THOSE
AREAS. SINCE THIS IS LATE IN THE SEASON FOR SUCH PATTERNS...THE
LOW CLOUDS AND FOG ARE EXPECTED TO BURN OFF IN THE AFTERNOONS AND
EVENINGS.

USUALLY AIR STAGNATION IS A CONCERN IN A PATTERN LIKE THIS...BUT
GIVEN THE EXPECTED AFTERNOON MIXING...WILL NOT ISSUE ANY
ADVISORIES AT THIS TIME.  

THE RIDGE WILL CONTINUE TO DRIFT EAST...AND WEAK SHORT WAVES
EJECTING FROM THE UPSTREAM TROUGH WILL START TO MOVE OVER THE
AREA WEDNESDAY. TYPICALLY THE FIRST SHORT WAVE AFTER A RIDGE HAS
LITTLE EFFECT OTHER THAN HERALDING THE END OF OFFSHORE LOW LEVEL
FLOW...AND THESE LOOK TOO WEAK TO DO MUCH OF ANYTHING. MORE SHORT
WAVES WILL FOLLOW THOUGH...PUSHING PROGRESSIVELY STRONGER FRONTS
ONSHORE. SO...PRECIPITATION WILL LIKELY RETURN SOMETIME IN THE
SECOND HALF OF NEXT WEEK. THE BEST GUESS FOR THE NEXT SIGNIFICANT
ROUND OF PRECIPITATION RIGHT NOW IS THURSDAY NIGHT...ALTHOUGH A
WEAK FRONT MAY BRING SOME LIGHT RAIN TO THE COAST AS EARLY AS
WEDNESDAY NIGHT.

&&

.AVIATION...FOR THE 07/06Z TAF CYCLE...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.
HOWEVER, WITH LOW DEWPOINTS AND SHALLOW MOISTURE LAYER EAST OF THE
CASCADES, CONFIDENCE IS NOT HIGH WITH THIS EAST OF THE CASCADES. FOG
AND LOW CLOUDS ARE EXPECTED TO GRADUALLY LIFT AND CLEAR TO VFR
BETWEEN 18-20Z SUNDAY.
/SVEN

&&

.MARINE...UPDATED 1000 PM PST SAT FEB 6 2016...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. /SVEN

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...NONE.

$$

15/15/09

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