Area Forecast Discussion
Issued by NWS Medford, OR

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

000
FXUS66 KMFR 222250
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
250 PM PST SUN NOV 22 2009

.DISCUSSION...COLD AIR ALOFT COMBINED WITH WEAKENING DYNAMICS AND
SOME UPSLOPE FLOW IS CAUSING SNOW SHOWERS OVER THE CASCADES WITH
ISOLATED RAIN SHOWERS IN THE COASTAL AREAS. UPSTREAM...A RIDGE IS
BUILDING AHEAD OF A STORM SYSTEM THAT WILL RIDE INTO THE GULF OF
ALASKA. THIS WILL REFLECT AS HIGH PRESSURE ON THE
SURFACE...INCREASING STABILITY OVER THE REGION AND ENDING ANY
SHOWERS. LIGHT WINDS...LONG NIGHTS...SURFACE HIGH PRESSURE AND
RECENT RAIN AND SNOWFALL IS A PERFECT SCENARIO FOR FOG DEVELOPING
IN THE VALLEYS IN THE WEST AND EAST SIDE. MONDAY THROUGH WEDNESDAY
WILL FEATURE FOG FORMING AFTER MIDNIGHT IN FAVORED VALLEYS. THE
FOG WILL LIFT TO LOW CLOUDS AND EVENTUALLY CLEAR AROUND NOON IN
MOST LOCATIONS. TUESDAY A WEAK COLD FRONT BRUSHES THE COASTAL
ZONES...BUT RAIN CHANCES ARE VERY LOW. CLEARING TIME WILL DICTATE
HOW WARM TEMPERATURES GET DURING THE FIRST HALF OF THE WEEK. CURRENT
FORECAST PRESENTS THE IDEA THAT WEDNESDAY WILL BE THE WARMEST DAY
AS GFS AND NAM AGREE THAT AIRMASS MAY BE 1-2 STANDARD DEVIATIONS
ABOVE AVERAGE BY THAT TIME. CLOUDS WILL BE MOSTLY OF THE MID AND
HIGH VARIETY THIS WEEK.

WEATHER FOR THANKSGIVING DAY TRAVEL IS GRADUALLY COMING INTO
FOCUS. GFS ENSEMBLE MEMBERS ALL INDICATE A SIMILAR IDEA OF AN
UPPER TROUGH AND COLD FRONT AFFECTING NORTHERN CALIFORNIA AND
OREGON BY THURSDAY AFTERNOON. SNOW LEVELS WILL INITIALLY BE
BETWEEN 5000 TO 7000 FEET BUT WILL FALL THURSDAY NIGHT AND END UP
AROUND 3500 FEET FRIDAY MORNING. THE ECMWF INDICATES MORE MOISTURE
THAN THE GFS SO WILL NEED TO MONITOR TRENDS IN THE NEAR-TERM. SISKIYOU PASS
WILL NOT LIKELY HAVE SIGNIFICANT SNOW IMPACTS WITH THIS WEATHER
SYSTEM. HOWEVER...AS COLD AIR FOLLOWS THE COLD FRONT...SOME SNOW
MAY ACCUMULATE AT PASS LEVEL LATE THURSDAY NIGHT OR EARLY FRIDAY
MORNING.



&&

.AVIATION...VFR CONDITIONS ARE EXPECTED TO CONTINUE AT ALL TAF
SITES THROUGH LATE TONIGHT WHEN FOG FORMS AT RBG AND
MFR...RESULTING IN IFR CONDITIONS THAT SHOULD LAST THROUGH MIDDAY
MONDAY. MOUNTAIN OBSCURATION WILL CONTINUE TO IMPACT MOST OF THE
HIGH TERRAIN THROUGH ABOUT 06Z WHEN DRY AIR BEGINS TO FILTER INTO
THE ELEVATED AREAS AND CLOUDS THERE DIMINISH.


&&

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

CA...NONE.

PACIFIC COASTAL WATERS...HAZARDOUS SEAS WARNING UNTIL 4 AM PST MONDAY
     FOR PZZ350-PZZ356-PZZ370-PZZ376.

$$

KEENE






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.