Area Forecast Discussion
Issued by NWS Medford, OR

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289
FXUS66 KMFR 091652
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
852 AM PST TUE FEB 9 2016

.DISCUSSION...PREVIOUS FORECAST IS ON TRACK. CURRENT VISIBLE
IMAGE SHOWS HIGH CLOUDS MOVING IN FROM THE SOUTHWEST INTO THE
SOUTHWEST PORTION OF THE AREA. THEY WILL CONTINUE TO MOVE
NORTHEAST DURING THE COURSE OF THE DAY. ALSO LOW CLOUDS AND
PATCHY FOG ARE MOSTLY CONFINED TO THE UMPQUA BASIN AND ILLINOIS
VALLEY. MADE A FEW ADJUSTMENTS TO THE CLOUD COVER AND WEATHER THIS
MORNING TO REFLECT CURRENT CONDITIONS. ALSO ADDED SOME CLOUD COVER
THIS AFTERNOON TO ACCOUNT FOR THE INCREASING HIGH AND MID LEVEL
CLOUDS.

THE RIDGE AXIS WILL SHIFT EAST AND GRADUALLY FLATTEN OUT SOME ON
WEDNESDAY AND THE MODELS SHOW LIGHT QPF AT THE COAST WITH THE NAM
SHOWING SOME QPF INLAND IN JOSEPHINE COUNTY, BUT SUSPECT THE NAM
MAY BE A BIT OVERDONE WITH THIS. OTHERWISE THE NEXT BEST CHANCE OF
PRECIPITATION MAY HOLD OFF UNTIL FRIDAY AS THE RIDGE AXIS SHIFTS
FURTHER EAST AND THE UPPER TROUGH APPROACHES THE OREGON COAST.
-PETRUCELLI

&&

.AVIATION...FOR THE 09/12Z TAF CYCLE...
OFFSHORE FLOW IS WEAKENING AND WILL CONTINUE TO WEAKEN TODAY. WHILE
LOW LEVEL WIND SHEAR COULD STILL BE AN ISSUE ON THE IMMEDIATE
WESTERN SIDE OF THE MOUNTAINS THROUGH ABOUT MIDDAY, NONE IS EXPECTED
DURING THE TAF PERIOD AT THE 4 PRIMARY AIRFIELDS. MEANWHILE, LIFR
LOW CLOUDS AND FOG ARE AGAIN PRESENT IN THE LOWER VALLEYS OF
JOSEPHINE AND DOUGLAS COUNTIES TO INCLUDE KRBG. THIS IS LIKELY TO
TAKE UNTIL MID AFTERNOON TO DISSIPATE. OTHERWISE, VFR CONDITIONS ARE
EXPECTED TO PREVAIL. BTL


&&

.MARINE...UPDATED 200 AM PST MON FEB 9 2016... LIGHT SOUTHEAST WINDS
THIS MORNING WILL SLOWLY INCREASE AS THEY BECOME SOUTH AND SOUTHWEST
THIS AFTERNOON THROUGH TONIGHT AS A WEAKENING FRONT APPROACHES. THIS
WEAKENING FRONT WILL MOVE IN VERY EARLY WEDNESDAY MORNING AND WILL
BE FOLLOWED BY ANOTHER FRONT LATE ON WEDNESDAY. ANOTHER FRONTAL
SYSTEM WILL AFFECT THE COASTAL WATERS THURSDAY INTO FRIDAY. WEST
SWELL WILL BUILD TO AROUND 15 FEET AT 18 SECONDS FRIDAY MORNING.
BTL


&&

.PREV DISCUSSION... /ISSUED 355 AM PST TUE FEB 9 2016/

SHORT TERM...STRONG RIDGING ALOFT WILL BEGIN TO WEAKEN AND SHIFT
EAST TODAY, AND THE SURFACE THERMAL TROUGH WILL SLIDE INLAND AS
WELL. IN A NORMAL SUMMER TIME RIDGING PATTERN, THIS WOULD SIGNAL
THE HOTTEST DAY OF THE STRETCH OVER INLAND AREAS. HOWEVER, I THINK
YESTERDAY`S RECORD BREAKING WARMTH WAS A FUNCTION OF THE INCREASED
MIXING DRIVEN BY DOWNSLOPING FLOW WHICH SHOULD BE LESS TODAY AS
GRADIENTS RELAX AND EVEN BECOME ONSHORE. GUIDANCE SHOWS 500 MB
HEIGHTS FALLING BY ABOUT 70 METERS AND 850 TEMPERATURES WILL BE
ABOUT 5C LOWER THAN YESTERDAY. ALL OF THIS MAKES A REPEAT OF
YESTERDAY UNLIKELY. THAT SAID, IT WILL STILL BE SUNNY AND
UNSEASONABLY WARM AGAIN OVER MOST INLAND SECTIONS WITH HIGH
TEMPERATURES AS MUCH AS 20 DEGREES ABOVE NORMAL. OR PUT ANOTHER
WAY: WE WOULD ONLY EXPECT TO SEE WEATHER THIS WARM IN FEBRUARY
ABOUT ONCE EVERY 5-10 YEARS. I DID BUMP TEMPERATURES UP OVER
INLAND AREAS A LITTLE TODAY, AND THE CURRENT FORECAST OF 71 IN
MEDFORD WOULD BE A RECORD IF CORRECT.

WE STILL HAVE OFFSHORE FLOW AT THE COAST THIS MORNING, AND THEY`LL
LIKELY GET WARM AFTER SUNRISE THIS MORNING. HOWEVER, ALL GUIDANCE
SHOWS THE FLOW BECOMING ONSHORE BY LATE MORNING TO EARLY
AFTERNOON, AND THIS WILL, OBVIOUSLY, PUT THE BREAKS ON ANY
WARMING. IN ADDITION, THERE IS A NOTICEABLE STRATUS SURGE ABOUT
200 MILES OFF BROOKINGS WHICH IS MAKING STEADY PROGRESS TOWARD THE
COAST. ALTHOUGH IT WON`T ARRIVE UNTIL AFTER SUNSET, IT IS A SIGN
OF THE CHANGING PATTERN.

LAST BUT NOT LEAST IS THE UMPQUA BASIN AROUND ROSEBURG WHERE
STRATUS TOOK FOREVER TO BURN OFF YESTERDAY. AS A RESULT, THEY
MISSED OUT ON THE WARMTH, AND STRATUS HAS ALREADY RETURNED AND
WILL LIKELY BE STUBBORN AGAIN TODAY, SO WE`RE STILL ONLY
FORECASTING HIGHS IN THE 50S THERE.

TEMPERATURES WILL FALL BACK CLOSER TO NORMAL ON WEDNESDAY AS THE
RIDGE AXIS MOVES INTO THE GREAT BASIN, OUR FLOW BECOMES WHOLLY
ONSHORE, AND CLOUDS BEGIN TO MOVE IN. WE MAY SEE SOME LIGHT RAIN
AT THE COAST BY LATE IN THE DAY WEDNESDAY AND ON INTO THURSDAY AS
WELL. HOWEVER, WE DON`T EXPECT TO SEE RAIN MAKE MUCH PROGRESS
INLAND UNTIL FRIDAY WHEN AN UPPER TROUGH FINALLY MOVES IN. FEW
CHANGES WERE MADE DURING THIS PERIOD, EXCEPT POPS WERE INCREASED
OVER THE WATERS AND COAST AND INTRODUCED A LITTLE EARLIER THAN
PREVIOUS FORECASTS. -WRIGHT

PREVIOUS LONG TERM DISCUSSION.../ISSUED 214 PM PST MON FEB 8
2016/

THE CONFIDENCE LESSENS OVER THE WEEKEND. THE RIDGE WILL TRY
TO REBUILD SATURDAY NIGHT THROUGH SUNDAY NIGHT, BUT MODEL
CONSENSUS INDICATES IT WILL REMAIN RELATIVELY FLAT WITH A WARM
FRONT PASSING TO THE NORTH. MODEL SPREAD IS SIGNIFICANT ENOUGH TO
PRECLUDE LARGE CHANGES TO THE FORECAST. THE 12Z GFS BUILDS THE
RIDGE FAIRLY ROBUSTLY, WHILE THE ECMWF/CANADIAN GEM REMAIN FLAT
ENOUGH THAT A PACIFIC DISTURBANCE CAN STILL BRING SOME RAIN,
MAINLY WEST OF THE CASCADES AND NORTH OF THE UMPQUA DIVIDE.
CONTINUITY LEANED MORE TOWARD THE WETTER SOLUTION AND HAVE LEFT
THIS MOSTLY AS IS.

BY MONDAY AND MONDAY NIGHT, MODELS SHOW A BREAK BETWEEN SYSTEMS,
SO HAVE KEPT THE FORECAST DRY THEN. SPILDE


&&

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

CA...NONE.

PACIFIC COASTAL WATERS...NONE.

$$



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