PDXAFDMFR (11/22/08 0826)

FXUS66 KMFR 221630
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
830 AM PST SAT NOV 22 2008

.DISCUSSION...12Z NGM/NAM/GFS IN.

LIGHT PRECIPITATION IS FALLING OVER MOST OF THE MEDFORD CWA FROM
THE CASCADES WEST AND SISKIYOUS NORTH THIS MORNING WITH VERY LITTLE
REPORTED ELSEWHERE. THIS PRECIPITATION IS ASSOCIATED WITH A WEAK COLD
FRONT THAT MOVED ONSHORE LAST NIGHT. THE REMNANTS OF THAT SYSTEM
WILL MOVE OUT OF THE CWA LATER TODAY AND HIGH PRESSURE WILL BUILD
IN ITS WAKE.

THE GLOBAL SCALE SHOWS A WAVE NUMBER OF 3 ACROSS THE
HEMISPHERE...WHICH IS NORMALLY ASSOCIATED WITH A NON-PROGRESSIVE
OR RETROGRESSIVE PATTERN. HOWEVER THIS WILL MORPH INTO A 4-WAVE
PROGRESSIVE PATTERN LATER TODAY.

A WEAK UPPER TROUGH OVER THE PACIFIC NORTHWEST WILL MOVE TO THE
EAST TODAY AND AN UPPER RIDGE WILL MOVE OVER THE WEST COAST THIS
EVENING. EXPECT PRECIPITATION TO END LATER TODAY WITH CLEARING
SKIES TONIGHT AND LOTS OF OVERNIGHT FOG IN THE WEST SIDE VALLEYS.
WEAK OFFSHORE LOW LEVEL FLOW WILL DEVELOP TONIGHT.  

THE RIDGE WILL MOVE ON TOMORROW AND THEN THE PICTURE GETS A BIT
MORE COMPLICATED. THE INCOMING UPPER TROUGH WILL SHEAR AS IT
CROSSES 135W. THE NORTHERN PORTION OF THE TROUGH WILL WEAKEN
GREATLY AS IT MOVES TO THE NORTHEAST AND WILL NOT BE A FACTOR FOR
THE MEDFORD CWA. THE SHEARED PORTION OF THE TROUGH WILL FORM A
CUTOFF LOW NEAR 35N 130W MONDAY. FROM HERE ON OUT THE PICTURE
BECOMES A BIT MURKIER. THE FORECAST MODELS VARY ON ITS HANDLING OF
THIS CUTOFF...BUT AS OF THIS MORNING MOST OF THEM ARE CONVERGING
ON MOVING THE LOW EAST INTO THE CENTRAL CALIFORNIA COAST EARLY
WEDNESDAY. AS THIS OCCURS THE MEDFORD CWA WILL COME UNDER
NORTHERLY FLOW ALOFT MONDAY NIGHT...WHICH WILL BECOME
NORTHWESTERLY AS THE CUTOFF APPROACHES THE CENTRAL CALIFORNIA
COAST TUESDAY. EXPECT WEAK OFFSHORE FLOW TO PERSIST THROUGH MONDAY
WITH CONTINUED DRY WEATHER. SOME LIGHT PRECIPITATION ASSOCIATED
WITH THE CUTOFF MAY EDGE INTO THE NORTHERN CALIFORNIA ZONES TUESDAY
AND INTO THE OREGON AREAS TUESDAY NIGHT. AMOUNTS WILL BE QUITE
LIGHT.

PRECIPITATION WILL END WEDNESDAY AS THE LOW MOVES OUT AND A SHORT
WAVE RIDGE MOVES THROUGH.  

THANKSGIVING DAY...THE CURRENT MODEL RUNS BRING A COLD SHORT WAVE
DISTURBANCE DOWN THE BACK SIDE OF THE TROUGH CREATED BY THE
TUESDAY- WEDNESDAY SYSTEM. THIS COULD BRING SOME WINTER WEATHER
DOWN TO THE PASS LEVELS AT THAT TIME.  

FRIDAY AND SATURDAY...A BROAD TROUGH WILL PERSIST OVER THE
AREA...THOUGH MOST OF THE PRECIPITATION ENERGY SHOULD BE SOUTH.
THEREFORE...WILL GO WITH A DRY BUT COOL FORECAST FOR NOW.

&&

.AVIATION...AREAS OF MVFR CIGS WITH ISOLATED IFR CIGS/VSBYS THIS
MORNING FROM THE CASCADES WEST AND SISKIYOUS NORTH WILL CLEAR TO
VFR LATER TODAY. IFR CIGS/VSBYS WILL RETURN TO THE WEST SIDE
VALLEYS TONIGHT WHILE VFR CONDITIONS WILL PERSIST ON THE RIDGES.
EAST OF THE CASCADES AND SOUTH OF THE SISKIYOUS...VFR WITH LCL
MVFR CIGS WILL CLEAR TO VFR LATER TODAY AND REMAIN VFR THROUGH
SUNDAY MORNING.


&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS 
     UNTIL 9 PM PST THIS EVENING FOR PZZ350-PZZ356-PZZ370-PZZ376.



15/15/15