Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 172206
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
206 PM PST WED DEC 17 2014

.DISCUSSION...ANOTHER WEAK UPPER TROUGH IS NEAR THE COAST AND THIS
WILL MOVE INLAND THIS EVENING. CURRENT RADAR SHOWS TWO AREAS OF
SCATTERED SHOWERS. THE FIRST IS IN NORTHEAST SISKIYOU AND KLAMATH
COUNTY AND THE SECOND IS MOVING TOWARDS THE COAST. THIS SECOND
FEATURE WILL MOVE INLAND THIS EVENING AND BRING SCATTERED SHOWERS
OVER NORTHERN CAL AND SOUTHWEST OREGON. THE LATEST RAP MODELS
DEPICTS THE PLACEMENT OF THE PRECIPITATION WELL AND WILL FOLLOW THIS
FOR THIS EVENING. THE UPPER TROUGH WILL WEAKEN AS IT MOVES EAST AND
SHORTWAVE RIDGING BEGINS TO BUILD IN OVERNIGHT. THIS SHOULD SHUT OFF
THE SHOWER ACTIVITY OVER MOST OF THE AREA, ALTHOUGH SOME RESIDUAL
SHOWERS COULD LINGER IN SOUTHEAST SISKIYOU AND MODOC COUNTIES.

WE`LL CATCH A DRY BREAK ON THURSDAY WITH THE RIDGE AXIS OVER THE
AREA, BUT THIS WILL BE SHORT LIVED. THE MODELS SHOW A STRONGER FRONT
APPROACHING THE AREA THURSDAY AFTERNOON BRINGING INCREASING SOUTH
WINDS OVER THE MARINE WATERS WHICH ARE EXPECTED TO GET CLOSE TO
GALES. PRECIPITATION COULD ALSO REACH THE COAST AS EARLY AS THURSDAY
AFTERNOON. THE FRONT WILL MOVE INLAND THURSDAY NIGHT BRINGING
MODERATE TO HEAVY PRECIPITATION OVER THE USUAL SUSPECTS...THE COAST
RANGE...COASTAL MOUNTAINS AND CASCADES. HOWEVER THE MODELS ARE IN
GOOD AGREEMENT THE FRONT WILL BE A QUICK MOVER AND SO WE WON`T GET
SIGNIFICANT PRECIPITATION AMOUNTS. SNOW LEVELS WILL START OUT HIGH
THURSDAY NIGHT, BUT WILL DROP TO AROUND 4500 FEET EARLY FRIDAY
MORNING. SO IT`S A GOOD BET THE MOUNTAIN PASSES WILL GET
ACCUMULATING SNOW STARTING LATE THURSDAY NIGHT THROUGH FRIDAY
MORNING. CURRENT THINKING IS CRATER LAKE COULD PICK UP AT LEAST 6
INCHES OR MORE AND A FEW INCHES ARE POSSIBLE OVER SISKIYOU SUMMIT
AND HIGHWAY 140. KEEP IN MIND THE DETAILS ON THIS WILL CHANGE, SO
STAY TUNED FOR THE LATEST UPDATES.

THE ABOVE MENTIONED FRONT WILL QUICKLY MOVE THROUGH FRIDAY AND WE`LL
CATCH A RELATIVE BREAK IN PRECIPITATION FRIDAY AFTERNOON AND EVENING.
BUT AGAIN THIS WILL BE SHORT LIVED. THE MODELS ARE IN PRETTY GOOD
AGREEMENT SHOWING A STRONG WARM FRONT ARRIVING AT THE COAST LATE
FRIDAY NIGHT AND MOVING OVER THE AREA SATURDAY. THIS FRONT HAS A LOT
OF JUICE WITH IT AND HEAVY PRECIPITATION WILL LIKELY IMPACT THE
COAST...COAST RANGE...COASTAL MOUNTAINS AND CASCADES. MODERATE TO
HEAVY PRECIPITATION WILL ALSO IMPACT MUCH OF THE WESTSIDE VALLEYS. OF
NOTE THE IVT TRANSPORT (WHICH IS GFS BASED) PUTS THE HIGHEST VALUES
IN CENTRAL AND NORTHWEST OREGON. EVEN THE GEFS ENSEMBLE MEAN IS
SIMILAR TO THE OPERATIONAL GFS. ADDITIONALY, THE UPPER FLOW IS
ALMOST DUE WEST WHICH WILL SQUEEZE OUT EVEN MORE MOISTURE ALONG THE
COAST RANGE. ALSO WINDS WILL INCREASE AHEAD OF THE FRONT AND THERE
IS A CHANCE FOR GALE FORCE WINDS OVER THE MARINE WATERS AND MODERATE
TO STRONG WINDS OVER THE COAST AND HEADLANDS. IF THAT WEREN`T ENOUGH
THERE IS CONCERN FOR SNOW EAST OF THE CASCADES AS THE WARM FRONT
ARRIVES. MODEL SOUNDINGS SUPPORT THE IDEA THAT ENOUGH COLD AIR WILL
BE PRESENT NEAR THE SURFACE AND THIS IN COMBINATION WITH OVERRUNNING
PRECIPITATION COULD BRING A PERIOD OF SNOW SATURDAY MORNING.

STRONG WESTERLY FLOW CONTINUES SATURDAY NIGHT WITH THE HEAVIEST
PRECIPITATION WEST OF THE CASCADES, BUT SNOW LEVELS WILL JUMP UP TO
AROUND 7000 FEET SATURDAY AFTERNOON AND REMAIN HIGH SATURDAY NIGHT.
-PETRUCELLI

LONG-TERM FORECAST...SUNDAY THROUGH WEDNESDAY.  A BROAD LONG WAVE
RIDGE WILL BE IN PLACE AT THE BEGINNING OF THE EXTENDED PERIOD WITH
WITH GENERALLY NORTHWEST FLOW ALOFT. SHORT WAVES RIDING OVER THE TOP
OF THE RIDGE WILL WEAKEN IT FROM SUNDAY NIGHT ON...BUT IT WILL
REMAIN IN PLACE THROUGH TUESDAY. THE FLOW ALOFT WILL BECOME MORE
ZONAL TUESDAY.

THIS PATTERN WILL FORCE THE MAIN STORM TRACK TO THE NORTH OF THE
MEDFORD CWA...BUT THE AREA WILL STILL CATCH THE SOUTHERN END OF
SEVERAL SYSTEMS WHICH WILL MOVE ONSHORE DURING THIS INTERVAL. THE
STRONGEST OF THESE SYSTEMS WILL MOVE ONSHORE SATURDAY AFTERNOON AND
EVENING...AND WILL BE OVER THE CWA SUNDAY. REINFORCING SHORT WAVES
WILL KEEP THE PRECIPITATION GOING THROUGH MOST OF MONDAY. THE BULK
OF THE ASSOCIATED PRECIPITATION WILL FALL ALONG THE COAST...COAST
RANGE...AND UMPQUA BASIN. AMOUNTS WILL BE SIGNIFICANT BUT NOT
EXCESSIVE...NO FLOODING PROBLEMS ARE ANTICIPATED. SNOW LEVELS WILL
BE ABOVE 7000 FEET.

MONDAY NIGHT INTO TUESDAY LOOK TO BE MOSTLY DRY WITH NEARLY ALL THE
ACTION TO THE NORTH OF THE AREA.

THE RIDGE WILL BREAK DOWN WEDNESDAY AND A LONG WAVE TROUGH WILL
BEGIN TO DIG OFFSHORE.  THIS CHANGE IN PATTERN WILL SUPPORT A FRONT
MOVING ONSHORE WEDNESDAY. THIS WILL BE THE WETTEST SYSTEM OF THE
EXTENDED PERIOD IF THE CURRENT EC/GFS MODEL SOLUTIONS PAN OUT. SNOW
LEVELS MAY ALSO FALL AS LOW AS 4000 FEET BEHIND THE FRONT WEDNESDAY
NIGHT...SO SNOW MAY RETURN TO THE PASSES AROUND THAT TIME. -JRS


&&

.AVIATION...BASED ON THE 17/18Z TAF CYCLE...VFR CONDITIONS WILL
PREVAIL INITIALLY WITH AREAS OF HIGHER TERRAIN OBSCURED...EXCEPT FOR
WESTERN AND SOUTH CENTRAL SISKIYOU COUNTY...WHERE AREAS OF MVFR CIGS
WILL PREVAIL THROUGH THURSDAY MORNING.  WIDESPREAD MVFR CIGS AND
AREAS OF IFR CIGS/VSBYS WILL RETURN TO THE WEST SIDE TONIGHT. KOTH
WILL BE AFFECTED BY THE MVFR CIGS AND KRBG AND KMFR WILL BE
AFFECTED BY THE IFR CIGS/VSBYS. ALL AREAS WILL CLEAR TO VFR BY
THURSDAY AFTERNOON. -JRS


&&

.MARINE...UPDATED 935 AM PST WED DEC 17 2014...WEAK LOW PRESSURE
SYSTEMS WILL MOVE THROUGH THE AREA TODAY AND TONIGHT. SOUTHWEST
SWELL DOMINATED SEAS WILL REMAIN MOSTLY AT OR ABOVE 10 FEET TODAY.
THURSDAY INTO THURSDAY NIGHT A STRONGER FRONTAL SYSTEM WILL LIKELY
BRING GALE FORCE WINDS AND VERY STEEP SOUTHWEST SEAS. HEAVY WEST
SWELL WILL BEGIN TO ARRIVE IN THE PREDAWN HOURS FRIDAY MORNING. IT
WILL PEAK FRIDAY NIGHT AT AROUND 19 FEET AT 18 SECONDS. A WARM FRONT
WILL MOVE THROUGH FRIDAY NIGHT...FOLLOWED BY A COLD FRONT SATURDAY.
OFFSHORE HIGH PRESSURE WILL BUILD SATURDAY NIGHT INTO SUNDAY. -JRS


&&

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

CA...NONE.

PACIFIC COASTAL WATERS...GALE WATCH FROM THURSDAY MORNING THROUGH THURSDAY EVENING FOR
     PZZ350-356-370-376.
     HAZARDOUS SEAS WATCH FROM THURSDAY AFTERNOON THROUGH LATE
     THURSDAY NIGHT FOR PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 PM PST THIS
     AFTERNOON FOR PZZ350-356-370-376.

$$


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