000
FXUS66 KMFR 200507
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
900 PM PST WED NOV 19 2008
.DISCUSSION...THE STABLE PATTERN UNDER HIGH PRESSURE WILL SOON BREAK
DOWN. HOWEVER IT REMAINS STABLE UNDER THE WARM FRONT SO FOGS ARE
DEVELOPING IN THE WESTERN VALLEYS. THE FOGS SHOULD NOT LAST THE WHOLE
NIGHT. AN APPROACHING COLD FRONT WILL MIX OUT STAGNANT VALLEY AIR
LATE TONIGHT AND THURSDAY MORNING. IT IS LIKELY TO PROVIDE LIGHT TO
MODERATE PRECIPITATION TO MOST OF OUR REGION. SNOW LEVELS WILL
INITIALLY BE ABOUT 6000 TO 6500 FEET THEN FALL TO 4000 TO 5000
FEET THURSDAY MORNING BEHIND THE FRONT. THUS...AN ACCUMULATION OF
AS MUCH AS 3 INCHES OF SNOW IS POSSIBLE OVER MOUNTAIN PASSES
THURSDAY MORNING. THIS IS NOT ENOUGH TO WARRANT A WINTER WEATHER
ADVISORY BUT THERE COULD BE HAZARDOUS DRIVING CONDITIONS THURSDAY
MORNING WITH A FEW FLURRIES LINGERING THURSDAY AFTERNOON AND EVENING.
HIGH PRESSURE WILL BRIEFLY BUILD BETWEEN SYSTEMS LATE THURSDAY
NIGHT INTO FRIDAY MORNING WITH AREAS OF VALLEY FOG IN SOUTHWEST
OREGON AND A FEW PATCHES ELSEWHERE.
THE NEXT UPPER TROUGH WILL MOVE INTO WESTERN CANADA LATE FRIDAY
THROUGH FRIDAY NIGHT. THE ASSOCIATED COLD FRONT WILL BE STRONGEST
FOR NORTHERN OREGON AND POINTS NORTHWARD BUT SUFFICIENTLY STRONG
FOR RAIN TO BE LIKELY IN SOUTHWEST OREGON AND A CHANCE IN SISKIYOU
AND KLAMATH COUNTIES FRIDAY NIGHT INTO SATURDAY MORNING. SNOW
LEVELS ARE AGAIN EXPECTED TO BE AROUND 5000 TO 6000 FEET FOR THE
LARGE MAJORITY OF THE EVENT WITH MINIMAL ACCUMULATIONS...UP TO 2
INCHES IN THE CASCADES.
HIGH PRESSURE ALOFT WILL BEGIN TO BUILD IN FROM THE WEST SATURDAY
AFTERNOON AND PERSIST INTO SUNDAY EVENING. THUS...THE MAIN
WEATHER FEATURE OF INTEREST FOR MOST OF THE WEEKEND WILL BE
VALLEY FOG.
IN A BIT OF A ROLE REVERSAL FROM THE NORMAL MODEL BIASES...THE
ECMWF IS WEAKER WITH THE WEEKEND RIDGE AND THUS FASTER IN MOVING
IN THE NEXT WEATHER SYSTEM EARLY NEXT WEEK.
GIVEN THE WIDE DISPARITIES IN MODEL SOLUTIONS...THE FORECAST FOR
NEXT WEEK BEYOND SUNDAY NIGHT REFLECTS A BROAD BRUSH LEANING
TOWARD THE ECMWF TIMING AND THE EXPECTATION OF AN ACTIVE PATTERN
WITH PERIODS OF PRECIPITATION. THE HIGHEST PROBABILITY FOR NEXT
WEEK IS THAT LIGHT TO MODERATE SNOW WILL CREATE TRAVEL ISSUES AT
TIMES OVER MOUNTAIN PASSES INCLUDING SISKIYOU SUMMIT BUT THE LOWER
ATMOSPHERE MOSTLY REMAINING MIXED WILL BE GOOD NEWS FOR AIR
TRAVELERS AND AT THIS TIME NONE OF THE WEATHER SYSTEMS LOOK TO BE
ESPECIALLY STRONG OR COLD.
&&
.AVIATION...CONDITIONS WILL REMAIN VFR THIS EVENING THEN A COLD
FRONT WILL REACH THE COAST AFTER MIDNIGHT. MVFR AND LOCAL IFR
CONDITIONS ASSOCIATED WITH THE FRONT WILL SPREAD INLAND THURSDAY
MORNING BUT THE IFR WILL BE MOSTLY AS MOUNTAIN OBSCUREMENT.
THE FRONT WILL WEAKEN EAST OF THE CASCADES IN THE AFTERNOON BUT POST
FRONTAL SHOWERS WILL MAINTAIN OBSCURATIONS OF MOST OF THE HIGHER
TERRAIN IN THE REGION INCLUDING THE CASCADES AND SISKIYOUS.
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...AIR STAGNATION ADVISORY UNTIL 10 PM PST THIS EVENING FOR ORZ023-
ORZ024-ORZ026-ORZ029.
CA...NONE.
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS FROM 10 PM
THIS EVENING TO 4 AM PST THURSDAY FOR PZZ350-PZZ356-PZZ370-
PZZ376.
HAZARDOUS SEAS WARNING FROM 10 AM THURSDAY TO 4 PM PST SATURDAY
FOR PZZ350-PZZ356-PZZ370-PZZ376.
GALE WARNING FROM 4 AM TO 10 AM PST THURSDAY FOR PZZ350-PZZ356-
PZZ370-PZZ376.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 10 PM THIS EVENING
TO 10 AM PST THURSDAY FOR PZZ350-PZZ356-PZZ370-PZZ376.
$$
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