FXUS66 KMFR 271601
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
801 AM PST FRI NOV 27 2009

.DISCUSSION...27/12Z NAM IN. 27/12Z GFS IN THROUGH 72HR.

THE BACK EDGE OF A COLD FRONT IS NOW MOVING THROUGH LAKE AND MODOC
COUNTIES AND WILL CLEAR TO THE EAST OF THE MEDFORD CWA LATER TODAY.
LIGHT POST-FRONTAL SHOWERS ARE SCATTERED THROUGHOUT THE REMAINDER
OF THE CWA. THOSE SHOWERS ARE BEING FUELED BY COLD AIR ALOFT
ASSOCIATED WITH AN UPPER TROUGH THAT IS NOW IN THE PROCESS OF
SHEARING. THE NORTHERN PART WILL MOVE TO THE EAST OF THE CWA THIS
EVENING WHILE THE SHEARED CUTOFF LOW WILL SET UP OVER CENTRAL
CALIFORNIA. EXPECT THE SHOWERS TO END THIS EVENING.  

AN UPPER RIDGE WILL BUILD OVER THE AREA IN THE WAKE OF THE
TROUGH...AND THIS WILL BRING DRY WEATHER TO THE CWA. AS THE RIDGE
MOVES IN...A WARM FRONT WILL MOVE THROUGH THE AREA. AT THIS TIME
IT APPEARS IT WILL BE A DRY ONE. WEAK OFFSHORE FLOW WILL DEVELOP
TONIGHT AND PEAK SATURDAY NIGHT. WHILE THIS WILL BRING MOSTLY
CLEAR SKIES AND WARMER TEMPERATURES TO RIDGES AND PARTS OF THE
COAST...IT WILL ALSO ALLOW STRONG INVERSIONS TO DEVELOP OVER THE
WESTERN VALLEYS...TRAPPING COLD AIR AND CLOUDS IN THOSE LOCATIONS.

THE OFFSHORE FLOW REGIME WILL END MONDAY BUT THE DRY WEATHER WILL
CONTINUE. STRONG OFFSHORE RIDGE PATTERNS SUCH AS THIS USUALLY COME
TO AN END WHEN A LOW UNDERCUTS THE RIDGE...AND THE MODELS INDICATE
THAT THIS WILL BE THE CASE THIS TIME AS WELL. HOWEVER...WHILE THE
MEDIUM-RANGE MODELS DO AGREE ON THE TIMING OF THIS EVENT...
BRINGING A LOW TO THE COAST IN THE TUESDAY NIGHT TO WEDNESDAY TIME
FRAME...THEY DO VARY ON THE LOCATION OF THE LOW. THE 27/06Z DGEX
BRINGS IT INTO OREGON...WHILE THE 27/06Z GFS40 BRINGS IT INTO
NORTHERN CALIFORNIA. MEANWHILE THE 27/00Z ECMWF ADVECTS THE LOW
SOUTH ALONG THE COAST...LEAVING A RIDGE OVER OREGON. FROM THURSDAY
ON THE SOLUTION GETS MURKIER WITH THE GFS AND ECMWF 180 DEGREES
OUT OF PHASE.

&&

.AVIATION...AREAS OF MVFR CIGS IN SHOWERS WITH OBSCURATION OF
HIGHER TERRAIN WILL CLEAR TO VFR WITH ISOLATED MVFR CIGS THIS 
AFTERNOON. AREAS OF IFR CIGS/VSBYS WILL DEVELOP IN THE WESTERN
VALLEY LATE TONIGHT THROUGH SATURDAY MORNING.

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 10 PM 
        PST THIS EVENING FOR PZZ356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 AM PST MONDAY 
        FOR PZZ350-PZZ356.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 7 PM PST THIS EVENING FOR 
        PZZ350-PZZ370.
     HAZARDOUS SEAS WARNING UNTIL 10 PM PST THIS EVENING FOR PZZ370.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 10 PM PST SUNDAY FOR PZZ376.
     HAZARDOUS SEAS WARNING UNTIL 10 AM PST MONDAY FOR PZZ376.

$$

15/10/10