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000
FXUS66 KMFR 101157
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
357 AM PST TUE DEC 10 2013

.DISCUSSION...TEMPERATURES IN MOST AREAS THIS MORNING ARE RUNNING
ABOUT 5 TO 10 DEGREES HIGHER THAN AT THIS TIME YESTERDAY. THIS CAN
BE ATTRIBUTED TO SOME WARMING ALOFT, BUT ALSO HIGH CLOUDINESS
WHICH HAS STREAMED DOWN INTO THE AREA FROM THE NORTH OVERNIGHT.
EVEN SO, IT IS STILL VERY COLD WITH TEMPERATURES BELOW ZERO IN
SOME OF THE VALLEYS IN NORTHERN CALIFORNIA AND OVER THE EAST SIDE.
A STRONG INVERSION HAS WARMED THE MID SLOPES AND RIDGES WITH
TEMPERATURES JUST 1-3KFT OFF THE GROUND 20-30 DEGREES HIGHER.

HIGH PRESSURE OFFSHORE WILL WEAKEN OVER THE NEXT COUPLE OF DAYS AS
IT MOVES INLAND, BUT IT WILL KEEP US DRY THROUGH THURSDAY MORNING.
THERE`LL BE THE TYPICAL BOUTS OF LOW CLOUDS/FOG IN THE VALLEYS
WEST OF THE CASCADES EACH LATE-NIGHT AND EARLY MORNING. IT WILL
REMAIN COLDER THAN AVERAGE, BUT THE BITTER COLD WILL GRADUALLY
EASE. HIGHS TODAY IN MEDFORD WILL BE UP NEAR OR PERHAPS JUST ABOVE
FREEZING. IF IT EKES ABOVE FREEZING, IT WOULD BE THE FIRST TIME
SINCE LAST THURSDAY. IF IT DOESN`T, THAT`LL MAKE 5 CONSECUTIVE
DAYS BELOW FREEZING, WHICH HAS ONLY OCCURRED 5 TIMES SINCE RECORDS
HAVE BEEN KEPT. THE LONGEST STRETCH OF CONSECUTIVE DAYS 32F OR
LOWER WAS 9 ENDING 1/15/1930. THE PERSISTENT STRONG INVERSION
WILL MAINTAIN THE STAGNANT AIR MASS AND SINCE THE NEXT UPSTREAM
SYSTEM WILL BE SLOWER TO MOVE IN, I HAVE EXTENDED THE AIR
STAGNATION ADVISORY (NPWMFR) UNTIL NOON THURSDAY.

THE AFOREMENTIONED SYSTEM UPSTREAM WILL BREAK DOWN THE RIDGE
THURSDAY. TIMING OF ITS ARRIVAL IS IMPORTANT BECAUSE WE STILL
EXPECT COLD AIR TO BE TRAPPED IN THE VALLEYS THURSDAY MORNING.
MODELS HAVE BEEN SLOWING THIS SYSTEM DOWN AND IT LOOKS LIKE
PRECIPITATION WILL MOSTLY HOLD OFF UNTIL THURSDAY AFTERNOON. THIS
IS GOOD NEWS BECAUSE IT SHOULD ALLOW TEMPERATURES TO RISE ABOVE
FREEZING BEFORE PRECIPITATION ARRIVES. EVEN SO, WE HAVE LEFT A
SLIGHT CHANCE OF FREEZING RAIN IN THE FORECAST FOR THURSDAY
MORNING IN SOME OF THE WEST SIDE VALLEYS JUST IN CASE
PRECIPITATION ARRIVES SOONER. WE`LL BE TAKING A MUCH CLOSER LOOK
AT THIS OVER THE NEXT 24 HOURS OR SO.

IT SEEMS AS IF MODELS ARE ALSO TENDING TOWARD WEAKENING THESE
PACIFIC SYSTEMS AS THEY MOVE ONSHORE. THE ECMWF HAS BEEN THE
STRONGER OF THE MODELS...ALLOWING PRECIPITATION TO REACH
EAST/SOUTH OF THE CASCADES THURSDAY NIGHT INTO FRIDAY MORNING.
BUT THE GFS IS NOT AS BULLISH AND KEEPS MOST, IF NOT ALL
PRECIPITATION, ALONG AND WEST OF THE CASCADES. SIMILARLY THOUGH,
IF PRECIPITATION DOES MAKE IT EAST AND SOUTH OF THE CASCADES
THURSDAY NIGHT INTO FRIDAY, THERE IS A SLIGHT CHANCE AT SOME
FREEZING RAIN AGAIN IN THE DEEPER VALLEYS THAT GET COLD ENOUGH.
RIGHT NOW, IT LOOKS BY THEN THAT THE WEST SIDE VALLEYS SHOULD STAY
ABOVE FREEZING. SNOW LEVELS WILL BE 4500-5500 FEET AND THERE COULD
BE 1-3 INCHES IN THE CASCADES. PRECIPITATION WILL END FRIDAY
AFTERNOON WITH JUST A LITTLE LINGERING LIGHT RAIN NORTH OF THE
UMPQUA DIVIDE. HIGH PRESSURE WILL BUILD IN FRIDAY NIGHT AND
PERSIST INTO SATURDAY. THE NEXT WEAK FRONT WILL MOVE ONSHORE
SATURDAY NIGHT INTO SUNDAY, BUT AGAIN, LIGHT PRECIPITATION SHOULD
BE MOSTLY FROM THE CASCADES NORTH AND WEST. SPILDE

&&

.AVIATION...AREAS OF LOW CLOUDS AND FOG IN THE UMPQUA BASIN AND
THE ROGUE AND ILLINOIS VALLEYS THIS MORNING, PRIMARILY IN THE
LIFR TO IFR RANGE BECOMING VFR BY 21Z. VFR ELSEWHERE. SPILDE

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...FREEZE WATCH FROM LATE TONIGHT THROUGH WEDNESDAY MORNING FOR
     ORZ021.
     FREEZE WARNING UNTIL 8 AM PST THIS MORNING FOR ORZ021-022.
     AIR STAGNATION ADVISORY UNTIL NOON PST THURSDAY FOR
     ORZ023>026-028>031.

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 4 AM PST
     WEDNESDAY FOR PZZ376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 AM PST WEDNESDAY
     FOR PZZ376.

$$

MAS