FXUS66 KMFR 091643
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
843 AM PST WED DEC 9 2009

.DISCUSSION...NO CHANGES NECESSARY TO THE FORECAST THIS MORNING.
LOWS WERE GENERALLY IN THE TEENS AND 20S ON THE WEST SIDE AND AT
THE COAST EARLY THIS MORNING WITH TEMPERATURES WELL BELOW ZERO ON
THE EAST SIDE. HIGH TEMPERATURES WILL BE SIMILAR TO YESTERDAYS
VALUES UNDER MAINLY CLEAR SKIES. THE CWA REMAINS IN THE DRY
NORTHWEST FLOW ALOFT AND THIS WILL CONTINUE THROUGH TONIGHT.
TEMPERATURES TONIGHT WILL AGAIN BE UNSEASONABLY COLD BUT A FEW
DEGREES HIGHER THAN THE LOWS LAST NIGHT. CONSIDERABLE UNCERTAINTY
STILL EXISTS WITH THE TIMING AND STRENGTH OF THE SYSTEMS LATER
THIS WEEK INTO THE WEEKEND...AND THAT WILL BE THE FOCUS FOR THE
AFTERNOON PACKAGE.

&&

.AVIATION...VFR WITH GOOD VISIBILITY IS EXPECTED TODAY AND
TONIGHT WITH ONLY A FEW HIGH CLOUDS.

&&

.PREV DISCUSSION... /ISSUED 249 AM PST WED DEC 9 2009/ 

DISCUSSION...CONDITIONS OVER THE NEXT COUPLE OF DAYS WILL PRETTY 
MUCH MIMIC THE LAST FEW DAYS. A COLD AIR MASS REMAINS OVER THE
AREA THROUGH THURSDAY. CURRENT IR IMAGE SHOWS CLEAR SKIES OVER THE
ENTIRE CWA. SOUTHWEST OF THE CWA OVER THE PACIFIC A SPLIT FLOW
REGIME IS IN THE WORKS AS EVIDENT BY THE CLOUD COVER STRETCHING
AND DISSIPATING NEAR 42 N AND 130 W.

THE MAIN CONCERN FOR LATER IN THE WEEK INTO NEXT WEEKEND WILL BE THE 
ONSET OF MOISTURE AND RETREATING COLD AIR MASS. THE ECMWF AND NAM 
SHOW THE RIDGE OVER THE GULF OF ALASKA GETTING PINCHED OFF THURSDAY 
ALLOWING MOISTURE TO UNDERCUT THE RIDGE AND MOVE TOWARDS SOUTHWEST 
OREGON. THE GFS APPEARS TO BE THE OUTLIER SUGGESTING MOISTURE MOVES 
INTO SOUTHWEST OREGON THURSDAY AFTERNOON FOLLOWED BY A SURFACE LOW 
TRACKING UP THE OREGON COAST FRIDAY. I THINK THIS IS OVERDONE 
BECAUSE WE'LL REMAIN IN SPLIT FLOW WHICH USUALLY FAVORS A DRIER AND 
WEAKER SOLUTION. THEREFORE THE FORECAST FOR THURSDAY INTO THE 
WEEKEND WILL LEAN MORE TOWARDS A COMBINATION OF THE 
NAM...ECMWF...CANADIAN AND ENSEMBLE MEAN WHICH LOOKS MORE 
REASONABLE. 

MOST OF THE ENERGY FRIDAY AND SATURDAY WILL BE DIRECTED INTO 
NORTHERN CALIFORNIA. THIS WILL RESULT IN A LOW QPF EVENT FOR 
SOUTHERN OREGON. SNOW LEVELS WILL COME UP SATURDAY AND SUNDAY AS THE 
COLDER AIR GETS ADVECTED OUT. 

WEAK SHORTWAVE MOVES OVER THE AREA MONDAY BRINGING A RELATIVE BREAK 
IN THE WEATHER. BEYOND MONDAY...THE OPERATIONAL MODELS AND ENSEMBLE 
MEAN POINT TOWARDS A MILDER AND WETTER PATTERN FOR THE REST OF NEXT 
WEEK WITH A PARADE OF STORMS MOVING INTO SOUTHWEST OREGON. THEREFORE 
HAVE ADJUSTED POPS TO ABOVE CLIMO. 

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...FREEZE WATCH FROM THURSDAY EVENING THROUGH FRIDAY MORNING FOR 
     ORZ021-ORZ022.
     FREEZE WARNING UNTIL 9 AM PST THIS MORNING FOR ORZ021-ORZ022.
     FREEZE WARNING FROM 11 PM THIS EVENING TO 9 AM PST THURSDAY FOR 
     ORZ021-ORZ022.

CA...NONE.

PACIFIC COASTAL WATERS...NONE.

$$

MW